1PROC(5) Linux Programmer's Manual PROC(5)
2
6 proc - process information pseudo-filesystem
7
9 The proc filesystem is a pseudo-filesystem which provides an interface
10 to kernel data structures. It is commonly mounted at /proc. Typi‐
11 cally, it is mounted automatically by the system, but it can also be
12 mounted manually using a command such as:
13 mount -t proc proc /proc
15 Most of the files in the proc filesystem are read-only, but some files
17 are writable, allowing kernel variables to be changed.
18 Mount options
20 The proc filesystem supports the following mount options:
21 hidepid=n (since Linux 3.3)
23 This option controls who can access the information in
24 /proc/[pid] directories. The argument, n, is one of the follow‐
25 ing values:
26 0 Everybody may access all /proc/[pid] directories. This is
28 the traditional behavior, and the default if this mount
29 option is not specified.
30 1 Users may not access files and subdirectories inside any
32 /proc/[pid] directories but their own (the /proc/[pid]
33 directories themselves remain visible). Sensitive files
34 such as /proc/[pid]/cmdline and /proc/[pid]/status are now
35 protected against other users. This makes it impossible to
36 learn whether any user is running a specific program (so
37 long as the program doesn't otherwise reveal itself by its
38 behavior).
39 2 As for mode 1, but in addition the /proc/[pid] directories
41 belonging to other users become invisible. This means that
42 /proc/[pid] entries can no longer be used to discover the
43 PIDs on the system. This doesn't hide the fact that a
44 process with a specific PID value exists (it can be learned
45 by other means, for example, by "kill -0 $PID"), but it
46 hides a process's UID and GID, which could otherwise be
47 learned by employing stat(2) on a /proc/[pid] directory.
48 This greatly complicates an attacker's task of gathering
49 information about running processes (e.g., discovering
50 whether some daemon is running with elevated privileges,
51 whether another user is running some sensitive program,
52 whether other users are running any program at all, and so
53 on).
54 gid=gid (since Linux 3.3)
56 Specifies the ID of a group whose members are authorized to
57 learn process information otherwise prohibited by hidepid (i.e.,
58 users in this group behave as though /proc was mounted with
59 hidepid=0). This group should be used instead of approaches
60 such as putting nonroot users into the sudoers(5) file.
61 Files and directories
63 The following list describes many of the files and directories under
64 the /proc hierarchy.
65 /proc/[pid]
67 There is a numerical subdirectory for each running process; the
68 subdirectory is named by the process ID.
69 Each /proc/[pid] subdirectory contains the pseudo-files and
71 directories described below. These files are normally owned by
72 the effective user and effective group ID of the process. How‐
73 ever, as a security measure, the ownership is made root:root if
74 the process's "dumpable" attribute is set to a value other than
75 1. This attribute may change for the following reasons:
76 * The attribute was explicitly set via the prctl(2)
78 PR_SET_DUMPABLE operation.
79 * The attribute was reset to the value in the file
81 /proc/sys/fs/suid_dumpable (described below), for the reasons
82 described in prctl(2).
83 Resetting the "dumpable" attribute to 1 reverts the ownership of
85 the /proc/[pid]/* files to the process's real UID and real GID.
86 /proc/[pid]/attr
88 The files in this directory provide an API for security modules.
89 The contents of this directory are files that can be read and
90 written in order to set security-related attributes. This
91 directory was added to support SELinux, but the intention was
92 that the API be general enough to support other security mod‐
93 ules. For the purpose of explanation, examples of how SELinux
94 uses these files are provided below.
95 This directory is present only if the kernel was configured with
97 CONFIG_SECURITY.
98 /proc/[pid]/attr/current (since Linux 2.6.0)
100 The contents of this file represent the current security
101 attributes of the process.
102 In SELinux, this file is used to get the security context of a
104 process. Prior to Linux 2.6.11, this file could not be used to
105 set the security context (a write was always denied), since
106 SELinux limited process security transitions to execve(2) (see
107 the description of /proc/[pid]/attr/exec, below). Since Linux
108 2.6.11, SELinux lifted this restriction and began supporting
109 "set" operations via writes to this node if authorized by pol‐
110 icy, although use of this operation is only suitable for appli‐
111 cations that are trusted to maintain any desired separation
112 between the old and new security contexts. Prior to Linux
113 2.6.28, SELinux did not allow threads within a multi-threaded
114 process to set their security context via this node as it would
115 yield an inconsistency among the security contexts of the
116 threads sharing the same memory space. Since Linux 2.6.28,
117 SELinux lifted this restriction and began supporting "set" oper‐
118 ations for threads within a multithreaded process if the new
119 security context is bounded by the old security context, where
120 the bounded relation is defined in policy and guarantees that
121 the new security context has a subset of the permissions of the
122 old security context. Other security modules may choose to sup‐
123 port "set" operations via writes to this node.
124 /proc/[pid]/attr/exec (since Linux 2.6.0)
126 This file represents the attributes to assign to the process
127 upon a subsequent execve(2).
128 In SELinux, this is needed to support role/domain transitions,
130 and execve(2) is the preferred point to make such transitions
131 because it offers better control over the initialization of the
132 process in the new security label and the inheritance of state.
133 In SELinux, this attribute is reset on execve(2) so that the new
134 program reverts to the default behavior for any execve(2) calls
135 that it may make. In SELinux, a process can set only its own
136 /proc/[pid]/attr/exec attribute.
137 /proc/[pid]/attr/fscreate (since Linux 2.6.0)
139 This file represents the attributes to assign to files created
140 by subsequent calls to open(2), mkdir(2), symlink(2), and
141 mknod(2)
142 SELinux employs this file to support creation of a file (using
144 the aforementioned system calls) in a secure state, so that
145 there is no risk of inappropriate access being obtained between
146 the time of creation and the time that attributes are set. In
147 SELinux, this attribute is reset on execve(2), so that the new
148 program reverts to the default behavior for any file creation
149 calls it may make, but the attribute will persist across multi‐
150 ple file creation calls within a program unless it is explicitly
151 reset. In SELinux, a process can set only its own
152 /proc/[pid]/attr/fscreate attribute.
153 /proc/[pid]/attr/keycreate (since Linux 2.6.18)
155 If a process writes a security context into this file, all sub‐
156 sequently created keys (add_key(2)) will be labeled with this
157 context. For further information, see the kernel source file
158 Documentation/security/keys/core.rst (or file Documenta‐
159 tion/security/keys.txt on Linux between 3.0 and 4.13, or Docu‐
160 mentation/keys.txt before Linux 3.0).
161 /proc/[pid]/attr/prev (since Linux 2.6.0)
163 This file contains the security context of the process before
164 the last execve(2); that is, the previous value of
165 /proc/[pid]/attr/current.
166 /proc/[pid]/attr/socketcreate (since Linux 2.6.18)
168 If a process writes a security context into this file, all sub‐
169 sequently created sockets will be labeled with this context.
170 /proc/[pid]/autogroup (since Linux 2.6.38)
172 See sched(7).
173 /proc/[pid]/auxv (since 2.6.0-test7)
175 This contains the contents of the ELF interpreter information
176 passed to the process at exec time. The format is one unsigned
177 long ID plus one unsigned long value for each entry. The last
178 entry contains two zeros. See also getauxval(3).
179 Permission to access this file is governed by a ptrace access
181 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
182 /proc/[pid]/cgroup (since Linux 2.6.24)
184 See cgroups(7).
185 /proc/[pid]/clear_refs (since Linux 2.6.22)
187 This is a write-only file, writable only by owner of the
189 process.
190 The following values may be written to the file:
192 1 (since Linux 2.6.22)
194 Reset the PG_Referenced and ACCESSED/YOUNG bits for all
195 the pages associated with the process. (Before kernel
196 2.6.32, writing any nonzero value to this file had this
197 effect.)
198 2 (since Linux 2.6.32)
200 Reset the PG_Referenced and ACCESSED/YOUNG bits for all
201 anonymous pages associated with the process.
202 3 (since Linux 2.6.32)
204 Reset the PG_Referenced and ACCESSED/YOUNG bits for all
205 file-mapped pages associated with the process.
206 Clearing the PG_Referenced and ACCESSED/YOUNG bits provides a
208 method to measure approximately how much memory a process is
209 using. One first inspects the values in the "Referenced" fields
210 for the VMAs shown in /proc/[pid]/smaps to get an idea of the
211 memory footprint of the process. One then clears the PG_Refer‐
212 enced and ACCESSED/YOUNG bits and, after some measured time
213 interval, once again inspects the values in the "Referenced"
214 fields to get an idea of the change in memory footprint of the
215 process during the measured interval. If one is interested only
216 in inspecting the selected mapping types, then the value 2 or 3
217 can be used instead of 1.
218 Further values can be written to affect different properties:
220 4 (since Linux 3.11)
222 Clear the soft-dirty bit for all the pages associated
223 with the process. This is used (in conjunction with
224 /proc/[pid]/pagemap) by the check-point restore system to
225 discover which pages of a process have been dirtied since
226 the file /proc/[pid]/clear_refs was written to.
227 5 (since Linux 4.0)
229 Reset the peak resident set size ("high water mark") to
230 the process's current resident set size value.
231 Writing any value to /proc/[pid]/clear_refs other than those
233 listed above has no effect.
234 The /proc/[pid]/clear_refs file is present only if the CON‐
236 FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
237 /proc/[pid]/cmdline
239 This read-only file holds the complete command line for the
240 process, unless the process is a zombie. In the latter case,
241 there is nothing in this file: that is, a read on this file will
242 return 0 characters. The command-line arguments appear in this
243 file as a set of strings separated by null bytes ('\0'), with a
244 further null byte after the last string.
245 /proc/[pid]/comm (since Linux 2.6.33)
247 This file exposes the process's comm value—that is, the command
248 name associated with the process. Different threads in the same
249 process may have different comm values, accessible via
250 /proc/[pid]/task/[tid]/comm. A thread may modify its comm
251 value, or that of any of other thread in the same thread group
252 (see the discussion of CLONE_THREAD in clone(2)), by writing to
253 the file /proc/self/task/[tid]/comm. Strings longer than
254 TASK_COMM_LEN (16) characters are silently truncated.
255 This file provides a superset of the prctl(2) PR_SET_NAME and
257 PR_GET_NAME operations, and is employed by pthread_setname_np(3)
258 when used to rename threads other than the caller.
259 /proc/[pid]/coredump_filter (since Linux 2.6.23)
261 See core(5).
262 /proc/[pid]/cpuset (since Linux 2.6.12)
264 See cpuset(7).
265 /proc/[pid]/cwd
267 This is a symbolic link to the current working directory of the
268 process. To find out the current working directory of process
269 20, for instance, you can do this:
270 $ cd /proc/20/cwd; /bin/pwd
272 Note that the pwd command is often a shell built-in, and might
274 not work properly. In bash(1), you may use pwd -P.
275 In a multithreaded process, the contents of this symbolic link
277 are not available if the main thread has already terminated
278 (typically by calling pthread_exit(3)).
279 Permission to dereference or read (readlink(2)) this symbolic
281 link is governed by a ptrace access mode
282 PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
283 /proc/[pid]/environ
285 This file contains the initial environment that was set when the
286 currently executing program was started via execve(2). The
287 entries are separated by null bytes ('\0'), and there may be a
288 null byte at the end. Thus, to print out the environment of
289 process 1, you would do:
290 $ strings /proc/1/environ
292 If, after an execve(2), the process modifies its environment
294 (e.g., by calling functions such as putenv(3) or modifying the
295 environ(7) variable directly), this file will not reflect those
296 changes.
297 Furthermore, a process may change the memory location that this
299 file refers via prctl(2) operations such as PR_SET_MM_ENV_START.
300 Permission to access this file is governed by a ptrace access
302 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
303 /proc/[pid]/exe
305 Under Linux 2.2 and later, this file is a symbolic link contain‐
306 ing the actual pathname of the executed command. This symbolic
307 link can be dereferenced normally; attempting to open it will
308 open the executable. You can even type /proc/[pid]/exe to run
309 another copy of the same executable that is being run by process
310 [pid]. If the pathname has been unlinked, the symbolic link
311 will contain the string '(deleted)' appended to the original
312 pathname. In a multithreaded process, the contents of this sym‐
313 bolic link are not available if the main thread has already ter‐
314 minated (typically by calling pthread_exit(3)).
315 Permission to dereference or read (readlink(2)) this symbolic
317 link is governed by a ptrace access mode
318 PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
319 Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the
321 binary which was executed, and appears as a symbolic link. A
322 readlink(2) call on this file under Linux 2.0 returns a string
323 in the format:
324 [device]:inode
326 For example, [0301]:1502 would be inode 1502 on device major 03
328 (IDE, MFM, etc. drives) minor 01 (first partition on the first
329 drive).
330 find(1) with the -inum option can be used to locate the file.
332 /proc/[pid]/fd/
334 This is a subdirectory containing one entry for each file which
335 the process has open, named by its file descriptor, and which is
336 a symbolic link to the actual file. Thus, 0 is standard input,
337 1 standard output, 2 standard error, and so on.
338 For file descriptors for pipes and sockets, the entries will be
340 symbolic links whose content is the file type with the inode. A
341 readlink(2) call on this file returns a string in the format:
342 type:[inode]
344 For example, socket:[2248868] will be a socket and its inode is
346 2248868. For sockets, that inode can be used to find more
347 information in one of the files under /proc/net/.
348 For file descriptors that have no corresponding inode (e.g.,
350 file descriptors produced by bpf(2), epoll_create(2),
351 eventfd(2), inotify_init(2), perf_event_open(2), signalfd(2),
352 timerfd_create(2), and userfaultfd(2)), the entry will be a sym‐
353 bolic link with contents of the form
354 anon_inode:<file-type>
356 In many cases (but not all), the file-type is surrounded by
358 square brackets.
359 For example, an epoll file descriptor will have a symbolic link
361 whose content is the string anon_inode:[eventpoll].
362 In a multithreaded process, the contents of this directory are
364 not available if the main thread has already terminated (typi‐
365 cally by calling pthread_exit(3)).
366 Programs that take a filename as a command-line argument, but
368 don't take input from standard input if no argument is supplied,
369 and programs that write to a file named as a command-line argu‐
370 ment, but don't send their output to standard output if no argu‐
371 ment is supplied, can nevertheless be made to use standard input
372 or standard output by using /proc/[pid]/fd files as command-line
373 arguments. For example, assuming that -i is the flag designat‐
374 ing an input file and -o is the flag designating an output file:
375 $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...
377 and you have a working filter.
379 /proc/self/fd/N is approximately the same as /dev/fd/N in some
381 UNIX and UNIX-like systems. Most Linux MAKEDEV scripts symboli‐
382 cally link /dev/fd to /proc/self/fd, in fact.
383 Most systems provide symbolic links /dev/stdin, /dev/stdout, and
385 /dev/stderr, which respectively link to the files 0, 1, and 2 in
386 /proc/self/fd. Thus the example command above could be written
387 as:
388 $ foobar -i /dev/stdin -o /dev/stdout ...
390 Permission to dereference or read (readlink(2)) the symbolic
392 links in this directory is governed by a ptrace access mode
393 PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
394 Note that for file descriptors referring to inodes (pipes and
396 sockets, see above), those inodes still have permission bits and
397 ownership information distinct from those of the /proc/[pid]/fd
398 entry, and that the owner may differ from the user and group IDs
399 of the process. An unprivileged process may lack permissions to
400 open them, as in this example:
401 $ echo test | sudo -u nobody cat
403 test
404 $ echo test | sudo -u nobody cat /proc/self/fd/0
405 cat: /proc/self/fd/0: Permission denied
406 File descriptor 0 refers to the pipe created by the shell and
408 owned by that shell's user, which is not nobody, so cat does not
409 have permission to create a new file descriptor to read from
410 that inode, even though it can still read from its existing file
411 descriptor 0.
412 /proc/[pid]/fdinfo/ (since Linux 2.6.22)
414 This is a subdirectory containing one entry for each file which
415 the process has open, named by its file descriptor. The files
416 in this directory are readable only by the owner of the process.
417 The contents of each file can be read to obtain information
418 about the corresponding file descriptor. The content depends on
419 the type of file referred to by the corresponding file descrip‐
420 tor.
421 For regular files and directories, we see something like:
423 $ cat /proc/12015/fdinfo/4
425 pos: 1000
426 flags: 01002002
427 mnt_id: 21
428 The fields are as follows:
430 pos This is a decimal number showing the file offset.
432 flags This is an octal number that displays the file access
434 mode and file status flags (see open(2)). If the close-
435 on-exec file descriptor flag is set, then flags will also
436 include the value O_CLOEXEC.
437 Before Linux 3.1, this field incorrectly displayed the
439 setting of O_CLOEXEC at the time the file was opened,
440 rather than the current setting of the close-on-exec
441 flag.
442 mnt_id This field, present since Linux 3.15, is the ID of the
444 mount point containing this file. See the description of
445 /proc/[pid]/mountinfo.
446 For eventfd file descriptors (see eventfd(2)), we see (since
448 Linux 3.8) the following fields:
449 pos: 0
451 flags: 02
452 mnt_id: 10
453 eventfd-count: 40
454 eventfd-count is the current value of the eventfd counter, in
456 hexadecimal.
457 For epoll file descriptors (see epoll(7)), we see (since Linux
459 3.8) the following fields:
460 pos: 0
462 flags: 02
463 mnt_id: 10
464 tfd: 9 events: 19 data: 74253d2500000009
465 tfd: 7 events: 19 data: 74253d2500000007
466 Each of the lines beginning tfd describes one of the file
468 descriptors being monitored via the epoll file descriptor (see
469 epoll_ctl(2) for some details). The tfd field is the number of
470 the file descriptor. The events field is a hexadecimal mask of
471 the events being monitored for this file descriptor. The data
472 field is the data value associated with this file descriptor.
473 For signalfd file descriptors (see signalfd(2)), we see (since
475 Linux 3.8) the following fields:
476 pos: 0
478 flags: 02
479 mnt_id: 10
480 sigmask: 0000000000000006
481 sigmask is the hexadecimal mask of signals that are accepted via
483 this signalfd file descriptor. (In this example, bits 2 and 3
484 are set, corresponding to the signals SIGINT and SIGQUIT; see
485 signal(7).)
486 For inotify file descriptors (see inotify(7)), we see (since
488 Linux 3.8) the following fields:
489 pos: 0
491 flags: 00
492 mnt_id: 11
493 inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73
494 inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73
495 Each of the lines beginning with "inotify" displays information
497 about one file or directory that is being monitored. The fields
498 in this line are as follows:
499 wd A watch descriptor number (in decimal).
501 ino The inode number of the target file (in hexadecimal).
503 sdev The ID of the device where the target file resides (in
505 hexadecimal).
506 mask The mask of events being monitored for the target file
508 (in hexadecimal).
509 If the kernel was built with exportfs support, the path to the
511 target file is exposed as a file handle, via three hexadecimal
512 fields: fhandle-bytes, fhandle-type, and f_handle.
513 For fanotify file descriptors (see fanotify(7)), we see (since
515 Linux 3.8) the following fields:
516 pos: 0
518 flags: 02
519 mnt_id: 11
520 fanotify flags:0 event-flags:88002
521 fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73
522 The fourth line displays information defined when the fanotify
524 group was created via fanotify_init(2):
525 flags The flags argument given to fanotify_init(2) (expressed
527 in hexadecimal).
528 event-flags
530 The event_f_flags argument given to fanotify_init(2)
531 (expressed in hexadecimal).
532 Each additional line shown in the file contains information
534 about one of the marks in the fanotify group. Most of these
535 fields are as for inotify, except:
536 mflags The flags associated with the mark (expressed in hexadec‐
538 imal).
539 mask The events mask for this mark (expressed in hexadecimal).
541 ignored_mask
543 The mask of events that are ignored for this mark
544 (expressed in hexadecimal).
545 For details on these fields, see fanotify_mark(2).
547 /proc/[pid]/gid_map (since Linux 3.5)
549 See user_namespaces(7).
550 /proc/[pid]/io (since kernel 2.6.20)
552 This file contains I/O statistics for the process, for example:
553 # cat /proc/3828/io
555 rchar: 323934931
556 wchar: 323929600
557 syscr: 632687
558 syscw: 632675
559 read_bytes: 0
560 write_bytes: 323932160
561 cancelled_write_bytes: 0
562 The fields are as follows:
564 rchar: characters read
566 The number of bytes which this task has caused to be read
567 from storage. This is simply the sum of bytes which this
568 process passed to read(2) and similar system calls. It
569 includes things such as terminal I/O and is unaffected by
570 whether or not actual physical disk I/O was required (the
571 read might have been satisfied from pagecache).
572 wchar: characters written
574 The number of bytes which this task has caused, or shall
575 cause to be written to disk. Similar caveats apply here
576 as with rchar.
577 syscr: read syscalls
579 Attempt to count the number of read I/O operations—that
580 is, system calls such as read(2) and pread(2).
581 syscw: write syscalls
583 Attempt to count the number of write I/O operations—that
584 is, system calls such as write(2) and pwrite(2).
585 read_bytes: bytes read
587 Attempt to count the number of bytes which this process
588 really did cause to be fetched from the storage layer.
589 This is accurate for block-backed filesystems.
590 write_bytes: bytes written
592 Attempt to count the number of bytes which this process
593 caused to be sent to the storage layer.
594 cancelled_write_bytes:
596 The big inaccuracy here is truncate. If a process writes
597 1MB to a file and then deletes the file, it will in fact
598 perform no writeout. But it will have been accounted as
599 having caused 1MB of write. In other words: this field
600 represents the number of bytes which this process caused
601 to not happen, by truncating pagecache. A task can cause
602 "negative" I/O too. If this task truncates some dirty
603 pagecache, some I/O which another task has been accounted
604 for (in its write_bytes) will not be happening.
605 Note: In the current implementation, things are a bit racy on
607 32-bit systems: if process A reads process B's /proc/[pid]/io
608 while process B is updating one of these 64-bit counters,
609 process A could see an intermediate result.
610 Permission to access this file is governed by a ptrace access
612 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
613 /proc/[pid]/limits (since Linux 2.6.24)
615 This file displays the soft limit, hard limit, and units of mea‐
616 surement for each of the process's resource limits (see getr‐
617 limit(2)). Up to and including Linux 2.6.35, this file is pro‐
618 tected to allow reading only by the real UID of the process.
619 Since Linux 2.6.36, this file is readable by all users on the
620 system.
621 /proc/[pid]/map_files/ (since kernel 3.3)
623 This subdirectory contains entries corresponding to memory-
624 mapped files (see mmap(2)). Entries are named by memory region
625 start and end address pair (expressed as hexadecimal numbers),
626 and are symbolic links to the mapped files themselves. Here is
627 an example, with the output wrapped and reformatted to fit on an
628 80-column display:
629 # ls -l /proc/self/map_files/
631 lr--------. 1 root root 64 Apr 16 21:31
632 3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
633 ...
634 Although these entries are present for memory regions that were
636 mapped with the MAP_FILE flag, the way anonymous shared memory
637 (regions created with the MAP_ANON | MAP_SHARED flags) is imple‐
638 mented in Linux means that such regions also appear on this
639 directory. Here is an example where the target file is the
640 deleted /dev/zero one:
641 lrw-------. 1 root root 64 Apr 16 21:33
643 7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)
644 This directory appears only if the CONFIG_CHECKPOINT_RESTORE
646 kernel configuration option is enabled. Privilege
647 (CAP_SYS_ADMIN) is required to view the contents of this direc‐
648 tory.
649 /proc/[pid]/maps
651 A file containing the currently mapped memory regions and their
652 access permissions. See mmap(2) for some further information
653 about memory mappings.
654 Permission to access this file is governed by a ptrace access
656 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
657 The format of the file is:
659 address perms offset dev inode pathname
661 00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon
662 00651000-00652000 r--p 00051000 08:02 173521 /usr/bin/dbus-daemon
663 00652000-00655000 rw-p 00052000 08:02 173521 /usr/bin/dbus-daemon
664 00e03000-00e24000 rw-p 00000000 00:00 0 [heap]
665 00e24000-011f7000 rw-p 00000000 00:00 0 [heap]
666 ...
667 35b1800000-35b1820000 r-xp 00000000 08:02 135522 /usr/lib64/ld-2.15.so
668 35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522 /usr/lib64/ld-2.15.so
669 35b1a20000-35b1a21000 rw-p 00020000 08:02 135522 /usr/lib64/ld-2.15.so
670 35b1a21000-35b1a22000 rw-p 00000000 00:00 0
671 35b1c00000-35b1dac000 r-xp 00000000 08:02 135870 /usr/lib64/libc-2.15.so
672 35b1dac000-35b1fac000 ---p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
673 35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
674 35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870 /usr/lib64/libc-2.15.so
675 ...
676 f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0 [stack:986]
677 ...
678 7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0 [stack]
679 7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0 [vdso]
680 The address field is the address space in the process that the
682 mapping occupies. The perms field is a set of permissions:
683 r = read
685 w = write
686 x = execute
687 s = shared
688 p = private (copy on write)
689 The offset field is the offset into the file/whatever; dev is
691 the device (major:minor); inode is the inode on that device. 0
692 indicates that no inode is associated with the memory region, as
693 would be the case with BSS (uninitialized data).
694 The pathname field will usually be the file that is backing the
696 mapping. For ELF files, you can easily coordinate with the off‐
697 set field by looking at the Offset field in the ELF program
698 headers (readelf -l).
699 There are additional helpful pseudo-paths:
701 [stack]
703 The initial process's (also known as the main
704 thread's) stack.
705 [stack:<tid>] (since Linux 3.4)
707 A thread's stack (where the <tid> is a thread ID).
708 It corresponds to the /proc/[pid]/task/[tid]/ path.
709 [vdso] The virtual dynamically linked shared object. See
711 vdso(7).
712 [heap] The process's heap.
714 If the pathname field is blank, this is an anonymous mapping as
716 obtained via mmap(2). There is no easy way to coordinate this
717 back to a process's source, short of running it through gdb(1),
718 strace(1), or similar.
719 Under Linux 2.0, there is no field giving pathname.
721 /proc/[pid]/mem
723 This file can be used to access the pages of a process's memory
724 through open(2), read(2), and lseek(2).
725 Permission to access this file is governed by a ptrace access
727 mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).
728 /proc/[pid]/mountinfo (since Linux 2.6.26)
730 This file contains information about mount points in the
731 process's mount namespace (see mount_namespaces(7)). It sup‐
732 plies various information (e.g., propagation state, root of
733 mount for bind mounts, identifier for each mount and its parent)
734 that is missing from the (older) /proc/[pid]/mounts file, and
735 fixes various other problems with that file (e.g., nonextensi‐
736 bility, failure to distinguish per-mount versus per-superblock
737 options).
738 The file contains lines of the form:
74036 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
742(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
743 The numbers in parentheses are labels for the descriptions
745 below:
746 (1) mount ID: a unique ID for the mount (may be reused after
748 umount(2)).
749 (2) parent ID: the ID of the parent mount (or of self for the
751 root of this mount namespace's mount tree).
752 If the parent mount point lies outside the process's root
754 directory (see chroot(2)), the ID shown here won't have a
755 corresponding record in mountinfo whose mount ID (field 1)
756 matches this parent mount ID (because mount points that lie
757 outside the process's root directory are not shown in
758 mountinfo). As a special case of this point, the process's
759 root mount point may have a parent mount (for the initramfs
760 filesystem) that lies outside the process's root directory,
761 and an entry for that mount point will not appear in
762 mountinfo.
763 (3) major:minor: the value of st_dev for files on this filesys‐
765 tem (see stat(2)).
766 (4) root: the pathname of the directory in the filesystem which
768 forms the root of this mount.
769 (5) mount point: the pathname of the mount point relative to
771 the process's root directory.
772 (6) mount options: per-mount options.
774 (7) optional fields: zero or more fields of the form
776 "tag[:value]"; see below.
777 (8) separator: the end of the optional fields is marked by a
779 single hyphen.
780 (9) filesystem type: the filesystem type in the form
782 "type[.subtype]".
783 (10) mount source: filesystem-specific information or "none".
785 (11) super options: per-superblock options.
787 Currently, the possible optional fields are shared, master,
789 propagate_from, and unbindable. See mount_namespaces(7) for a
790 description of these fields. Parsers should ignore all unrecog‐
791 nized optional fields.
792 For more information on mount propagation see: Documenta‐
794 tion/filesystems/sharedsubtree.txt in the Linux kernel source
795 tree.
796 /proc/[pid]/mounts (since Linux 2.4.19)
798 This file lists all the filesystems currently mounted in the
799 process's mount namespace (see mount_namespaces(7)). The format
800 of this file is documented in fstab(5).
801 Since kernel version 2.6.15, this file is pollable: after open‐
803 ing the file for reading, a change in this file (i.e., a
804 filesystem mount or unmount) causes select(2) to mark the file
805 descriptor as having an exceptional condition, and poll(2) and
806 epoll_wait(2) mark the file as having a priority event (POLL‐
807 PRI). (Before Linux 2.6.30, a change in this file was indicated
808 by the file descriptor being marked as readable for select(2),
809 and being marked as having an error condition for poll(2) and
810 epoll_wait(2).)
811 /proc/[pid]/mountstats (since Linux 2.6.17)
813 This file exports information (statistics, configuration infor‐
814 mation) about the mount points in the process's mount namespace
815 (see mount_namespaces(7)). Lines in this file have the form:
816 device /dev/sda7 mounted on /home with fstype ext3 [statistics]
818 ( 1 ) ( 2 ) (3 ) (4)
819 The fields in each line are:
821 (1) The name of the mounted device (or "nodevice" if there is
823 no corresponding device).
824 (2) The mount point within the filesystem tree.
826 (3) The filesystem type.
828 (4) Optional statistics and configuration information. Cur‐
830 rently (as at Linux 2.6.26), only NFS filesystems export
831 information via this field.
832 This file is readable only by the owner of the process.
834 /proc/[pid]/net (since Linux 2.6.25)
836 See the description of /proc/net.
837 /proc/[pid]/ns/ (since Linux 3.0)
839 This is a subdirectory containing one entry for each namespace
840 that supports being manipulated by setns(2). For more informa‐
841 tion, see namespaces(7).
842 /proc/[pid]/numa_maps (since Linux 2.6.14)
844 See numa(7).
845 /proc/[pid]/oom_adj (since Linux 2.6.11)
847 This file can be used to adjust the score used to select which
848 process should be killed in an out-of-memory (OOM) situation.
849 The kernel uses this value for a bit-shift operation of the
850 process's oom_score value: valid values are in the range -16 to
851 +15, plus the special value -17, which disables OOM-killing
852 altogether for this process. A positive score increases the
853 likelihood of this process being killed by the OOM-killer; a
854 negative score decreases the likelihood.
855 The default value for this file is 0; a new process inherits its
857 parent's oom_adj setting. A process must be privileged
858 (CAP_SYS_RESOURCE) to update this file.
859 Since Linux 2.6.36, use of this file is deprecated in favor of
861 /proc/[pid]/oom_score_adj.
862 /proc/[pid]/oom_score (since Linux 2.6.11)
864 This file displays the current score that the kernel gives to
865 this process for the purpose of selecting a process for the OOM-
866 killer. A higher score means that the process is more likely to
867 be selected by the OOM-killer. The basis for this score is the
868 amount of memory used by the process, with increases (+) or
869 decreases (-) for factors including:
870 * whether the process is privileged (-).
872 Before kernel 2.6.36 the following factors were also used in the
874 calculation of oom_score:
875 * whether the process creates a lot of children using fork(2)
877 (+);
878 * whether the process has been running a long time, or has used
880 a lot of CPU time (-);
881 * whether the process has a low nice value (i.e., > 0) (+); and
883 * whether the process is making direct hardware access (-).
885 The oom_score also reflects the adjustment specified by the
887 oom_score_adj or oom_adj setting for the process.
888 /proc/[pid]/oom_score_adj (since Linux 2.6.36)
890 This file can be used to adjust the badness heuristic used to
891 select which process gets killed in out-of-memory conditions.
892 The badness heuristic assigns a value to each candidate task
894 ranging from 0 (never kill) to 1000 (always kill) to determine
895 which process is targeted. The units are roughly a proportion
896 along that range of allowed memory the process may allocate
897 from, based on an estimation of its current memory and swap use.
898 For example, if a task is using all allowed memory, its badness
899 score will be 1000. If it is using half of its allowed memory,
900 its score will be 500.
901 There is an additional factor included in the badness score:
903 root processes are given 3% extra memory over other tasks.
904 The amount of "allowed" memory depends on the context in which
906 the OOM-killer was called. If it is due to the memory assigned
907 to the allocating task's cpuset being exhausted, the allowed
908 memory represents the set of mems assigned to that cpuset (see
909 cpuset(7)). If it is due to a mempolicy's node(s) being
910 exhausted, the allowed memory represents the set of mempolicy
911 nodes. If it is due to a memory limit (or swap limit) being
912 reached, the allowed memory is that configured limit. Finally,
913 if it is due to the entire system being out of memory, the
914 allowed memory represents all allocatable resources.
915 The value of oom_score_adj is added to the badness score before
917 it is used to determine which task to kill. Acceptable values
918 range from -1000 (OOM_SCORE_ADJ_MIN) to +1000
919 (OOM_SCORE_ADJ_MAX). This allows user space to control the
920 preference for OOM-killing, ranging from always preferring a
921 certain task or completely disabling it from OOM killing. The
922 lowest possible value, -1000, is equivalent to disabling OOM-
923 killing entirely for that task, since it will always report a
924 badness score of 0.
925 Consequently, it is very simple for user space to define the
927 amount of memory to consider for each task. Setting an
928 oom_score_adj value of +500, for example, is roughly equivalent
929 to allowing the remainder of tasks sharing the same system,
930 cpuset, mempolicy, or memory controller resources to use at
931 least 50% more memory. A value of -500, on the other hand,
932 would be roughly equivalent to discounting 50% of the task's
933 allowed memory from being considered as scoring against the
934 task.
935 For backward compatibility with previous kernels,
937 /proc/[pid]/oom_adj can still be used to tune the badness score.
938 Its value is scaled linearly with oom_score_adj.
939 Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
941 change the other with its scaled value.
942 /proc/[pid]/pagemap (since Linux 2.6.25)
944 This file shows the mapping of each of the process's virtual
945 pages into physical page frames or swap area. It contains one
946 64-bit value for each virtual page, with the bits set as fol‐
947 lows:
948 63 If set, the page is present in RAM.
950 62 If set, the page is in swap space
952 61 (since Linux 3.5)
954 The page is a file-mapped page or a shared anonymous
955 page.
956 60–57 (since Linux 3.11)
958 Zero
959 56 (since Linux 4.2)
961 The page is exclusively mapped.
962 55 (since Linux 3.11)
964 PTE is soft-dirty (see the kernel source file Docu‐
965 mentation/vm/soft-dirty.txt).
966 54–0 If the page is present in RAM (bit 63), then these
968 bits provide the page frame number, which can be
969 used to index /proc/kpageflags and /proc/kpagecount.
970 If the page is present in swap (bit 62), then bits
971 4–0 give the swap type, and bits 54–5 encode the
972 swap offset.
973 Before Linux 3.11, bits 60–55 were used to encode the base-2 log
975 of the page size.
976 To employ /proc/[pid]/pagemap efficiently, use /proc/[pid]/maps
978 to determine which areas of memory are actually mapped and seek
979 to skip over unmapped regions.
980 The /proc/[pid]/pagemap file is present only if the CON‐
982 FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
983 Permission to access this file is governed by a ptrace access
985 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
986 /proc/[pid]/personality (since Linux 2.6.28)
988 This read-only file exposes the process's execution domain, as
989 set by personality(2). The value is displayed in hexadecimal
990 notation.
991 Permission to access this file is governed by a ptrace access
993 mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).
994 /proc/[pid]/root
996 UNIX and Linux support the idea of a per-process root of the
997 filesystem, set by the chroot(2) system call. This file is a
998 symbolic link that points to the process's root directory, and
999 behaves in the same way as exe, and fd/*.
1000 Note however that this file is not merely a symbolic link. It
1002 provides the same view of the filesystem (including namespaces
1003 and the set of per-process mounts) as the process itself. An
1004 example illustrates this point. In one terminal, we start a
1005 shell in new user and mount namespaces, and in that shell we
1006 create some new mount points:
1007 $ PS1='sh1# ' unshare -Urnm
1009 sh1# mount -t tmpfs tmpfs /etc # Mount empty tmpfs at /etc
1010 sh1# mount --bind /usr /dev # Mount /usr at /dev
1011 sh1# echo $$
1012 27123
1013 In a second terminal window, in the initial mount namespace, we
1015 look at the contents of the corresponding mounts in the initial
1016 and new namespaces:
1017 $ PS1='sh2# ' sudo sh
1019 sh2# ls /etc | wc -l # In initial NS
1020 309
1021 sh2# ls /proc/27123/root/etc | wc -l # /etc in other NS
1022 0 # The empty tmpfs dir
1023 sh2# ls /dev | wc -l # In initial NS
1024 205
1025 sh2# ls /proc/27123/root/dev | wc -l # /dev in other NS
1026 11 # Actually bind
1027 # mounted to /usr
1028 sh2# ls /usr | wc -l # /usr in initial NS
1029 11
1030 In a multithreaded process, the contents of the /proc/[pid]/root
1032 symbolic link are not available if the main thread has already
1033 terminated (typically by calling pthread_exit(3)).
1034 Permission to dereference or read (readlink(2)) this symbolic
1036 link is governed by a ptrace access mode
1037 PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
1038 /proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)
1040 This file can be used to read and change the process's secure
1041 computing (seccomp) mode setting. It contains the value 0 if
1042 the process is not in seccomp mode, and 1 if the process is in
1043 strict seccomp mode (see seccomp(2)). Writing 1 to this file
1044 places the process irreversibly in strict seccomp mode. (Fur‐
1045 ther attempts to write to the file fail with the EPERM error.)
1046 In Linux 2.6.23, this file went away, to be replaced by the
1048 prctl(2) PR_GET_SECCOMP and PR_SET_SECCOMP operations (and later
1049 by seccomp(2) and the Seccomp field in /proc/[pid]/status).
1050 /proc/[pid]/setgroups (since Linux 3.19)
1052 See user_namespaces(7).
1053 /proc/[pid]/smaps (since Linux 2.6.14)
1055 This file shows memory consumption for each of the process's
1056 mappings. (The pmap(1) command displays similar information, in
1057 a form that may be easier for parsing.) For each mapping there
1058 is a series of lines such as the following:
1059 00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash
1061 Size: 552 kB
1062 Rss: 460 kB
1063 Pss: 100 kB
1064 Shared_Clean: 452 kB
1065 Shared_Dirty: 0 kB
1066 Private_Clean: 8 kB
1067 Private_Dirty: 0 kB
1068 Referenced: 460 kB
1069 Anonymous: 0 kB
1070 AnonHugePages: 0 kB
1071 ShmemHugePages: 0 kB
1072 ShmemPmdMapped: 0 kB
1073 Swap: 0 kB
1074 KernelPageSize: 4 kB
1075 MMUPageSize: 4 kB
1076 KernelPageSize: 4 kB
1077 MMUPageSize: 4 kB
1078 Locked: 0 kB
1079 ProtectionKey: 0
1080 VmFlags: rd ex mr mw me dw
1081 The first of these lines shows the same information as is dis‐
1083 played for the mapping in /proc/[pid]/maps. The following lines
1084 show the size of the mapping, the amount of the mapping that is
1085 currently resident in RAM ("Rss"), the process's proportional
1086 share of this mapping ("Pss"), the number of clean and dirty
1087 shared pages in the mapping, and the number of clean and dirty
1088 private pages in the mapping. "Referenced" indicates the amount
1089 of memory currently marked as referenced or accessed. "Anony‐
1090 mous" shows the amount of memory that does not belong to any
1091 file. "Swap" shows how much would-be-anonymous memory is also
1092 used, but out on swap.
1093 The "KernelPageSize" line (available since Linux 2.6.29) is the
1095 page size used by the kernel to back the virtual memory area.
1096 This matches the size used by the MMU in the majority of cases.
1097 However, one counter-example occurs on PPC64 kernels whereby a
1098 kernel using 64kB as a base page size may still use 4kB pages
1099 for the MMU on older processors. To distinguish the two
1100 attributes, the "MMUPageSize" line (also available since Linux
1101 2.6.29) reports the page size used by the MMU.
1102 The "Locked" indicates whether the mapping is locked in memory
1104 or not.
1105 The "ProtectionKey" line (available since Linux 4.9, on x86
1107 only) contains the memory protection key (see pkeys(7)) associ‐
1108 ated with the virtual memory area. This entry is present only
1109 if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC‐
1110 TION_KEYS configuration option.
1111 The "VmFlags" line (available since Linux 3.8) represents the
1113 kernel flags associated with the virtual memory area, encoded
1114 using the following two-letter codes:
1115 rd - readable
1117 wr - writable
1118 ex - executable
1119 sh - shared
1120 mr - may read
1121 mw - may write
1122 me - may execute
1123 ms - may share
1124 gd - stack segment grows down
1125 pf - pure PFN range
1126 dw - disabled write to the mapped file
1127 lo - pages are locked in memory
1128 io - memory mapped I/O area
1129 sr - sequential read advise provided
1130 rr - random read advise provided
1131 dc - do not copy area on fork
1132 de - do not expand area on remapping
1133 ac - area is accountable
1134 nr - swap space is not reserved for the area
1135 ht - area uses huge tlb pages
1136 nl - non-linear mapping
1137 ar - architecture specific flag
1138 dd - do not include area into core dump
1139 sd - soft-dirty flag
1140 mm - mixed map area
1141 hg - huge page advise flag
1142 nh - no-huge page advise flag
1143 mg - mergeable advise flag
1144 "ProtectionKey" field contains the memory protection key (see
1146 pkeys(5)) associated with the virtual memory area. Present only
1147 if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC‐
1148 TION_KEYS configuration option. (since Linux 4.6)
1149 The /proc/[pid]/smaps file is present only if the CON‐
1151 FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
1152 /proc/[pid]/stack (since Linux 2.6.29)
1154 This file provides a symbolic trace of the function calls in
1155 this process's kernel stack. This file is provided only if the
1156 kernel was built with the CONFIG_STACKTRACE configuration
1157 option.
1158 Permission to access this file is governed by a ptrace access
1160 mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).
1161 /proc/[pid]/stat
1163 Status information about the process. This is used by ps(1).
1164 It is defined in the kernel source file fs/proc/array.c.
1165 The fields, in order, with their proper scanf(3) format speci‐
1167 fiers, are listed below. Whether or not certain of these fields
1168 display valid information is governed by a ptrace access mode
1169 PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT check (refer to
1170 ptrace(2)). If the check denies access, then the field value is
1171 displayed as 0. The affected fields are indicated with the
1172 marking [PT].
1173 (1) pid %d
1175 The process ID.
1176 (2) comm %s
1178 The filename of the executable, in parentheses. This
1179 is visible whether or not the executable is swapped
1180 out.
1181 (3) state %c
1183 One of the following characters, indicating process
1184 state:
1185 R Running
1187 S Sleeping in an interruptible wait
1189 D Waiting in uninterruptible disk sleep
1191 Z Zombie
1193 T Stopped (on a signal) or (before Linux 2.6.33)
1195 trace stopped
1196 t Tracing stop (Linux 2.6.33 onward)
1198 W Paging (only before Linux 2.6.0)
1200 X Dead (from Linux 2.6.0 onward)
1202 x Dead (Linux 2.6.33 to 3.13 only)
1204 K Wakekill (Linux 2.6.33 to 3.13 only)
1206 W Waking (Linux 2.6.33 to 3.13 only)
1208 P Parked (Linux 3.9 to 3.13 only)
1210 (4) ppid %d
1212 The PID of the parent of this process.
1213 (5) pgrp %d
1215 The process group ID of the process.
1216 (6) session %d
1218 The session ID of the process.
1219 (7) tty_nr %d
1221 The controlling terminal of the process. (The minor
1222 device number is contained in the combination of bits
1223 31 to 20 and 7 to 0; the major device number is in
1224 bits 15 to 8.)
1225 (8) tpgid %d
1227 The ID of the foreground process group of the control‐
1228 ling terminal of the process.
1229 (9) flags %u
1231 The kernel flags word of the process. For bit mean‐
1232 ings, see the PF_* defines in the Linux kernel source
1233 file include/linux/sched.h. Details depend on the
1234 kernel version.
1235 The format for this field was %lu before Linux 2.6.
1237 (10) minflt %lu
1239 The number of minor faults the process has made which
1240 have not required loading a memory page from disk.
1241 (11) cminflt %lu
1243 The number of minor faults that the process's waited-
1244 for children have made.
1245 (12) majflt %lu
1247 The number of major faults the process has made which
1248 have required loading a memory page from disk.
1249 (13) cmajflt %lu
1251 The number of major faults that the process's waited-
1252 for children have made.
1253 (14) utime %lu
1255 Amount of time that this process has been scheduled in
1256 user mode, measured in clock ticks (divide by
1257 sysconf(_SC_CLK_TCK)). This includes guest time,
1258 guest_time (time spent running a virtual CPU, see
1259 below), so that applications that are not aware of the
1260 guest time field do not lose that time from their cal‐
1261 culations.
1262 (15) stime %lu
1264 Amount of time that this process has been scheduled in
1265 kernel mode, measured in clock ticks (divide by
1266 sysconf(_SC_CLK_TCK)).
1267 (16) cutime %ld
1269 Amount of time that this process's waited-for children
1270 have been scheduled in user mode, measured in clock
1271 ticks (divide by sysconf(_SC_CLK_TCK)). (See also
1272 times(2).) This includes guest time, cguest_time
1273 (time spent running a virtual CPU, see below).
1274 (17) cstime %ld
1276 Amount of time that this process's waited-for children
1277 have been scheduled in kernel mode, measured in clock
1278 ticks (divide by sysconf(_SC_CLK_TCK)).
1279 (18) priority %ld
1281 (Explanation for Linux 2.6) For processes running a
1282 real-time scheduling policy (policy below; see
1283 sched_setscheduler(2)), this is the negated scheduling
1284 priority, minus one; that is, a number in the range -2
1285 to -100, corresponding to real-time priorities 1 to
1286 99. For processes running under a non-real-time
1287 scheduling policy, this is the raw nice value (setpri‐
1288 ority(2)) as represented in the kernel. The kernel
1289 stores nice values as numbers in the range 0 (high) to
1290 39 (low), corresponding to the user-visible nice range
1291 of -20 to 19.
1292 Before Linux 2.6, this was a scaled value based on the
1294 scheduler weighting given to this process.
1295 (19) nice %ld
1297 The nice value (see setpriority(2)), a value in the
1298 range 19 (low priority) to -20 (high priority).
1299 (20) num_threads %ld
1301 Number of threads in this process (since Linux 2.6).
1302 Before kernel 2.6, this field was hard coded to 0 as a
1303 placeholder for an earlier removed field.
1304 (21) itrealvalue %ld
1306 The time in jiffies before the next SIGALRM is sent to
1307 the process due to an interval timer. Since kernel
1308 2.6.17, this field is no longer maintained, and is
1309 hard coded as 0.
1310 (22) starttime %llu
1312 The time the process started after system boot. In
1313 kernels before Linux 2.6, this value was expressed in
1314 jiffies. Since Linux 2.6, the value is expressed in
1315 clock ticks (divide by sysconf(_SC_CLK_TCK)).
1316 The format for this field was %lu before Linux 2.6.
1318 (23) vsize %lu
1320 Virtual memory size in bytes.
1321 (24) rss %ld
1323 Resident Set Size: number of pages the process has in
1324 real memory. This is just the pages which count
1325 toward text, data, or stack space. This does not
1326 include pages which have not been demand-loaded in, or
1327 which are swapped out.
1328 (25) rsslim %lu
1330 Current soft limit in bytes on the rss of the process;
1331 see the description of RLIMIT_RSS in getrlimit(2).
1332 (26) startcode %lu [PT]
1334 The address above which program text can run.
1335 (27) endcode %lu [PT]
1337 The address below which program text can run.
1338 (28) startstack %lu [PT]
1340 The address of the start (i.e., bottom) of the stack.
1341 (29) kstkesp %lu [PT]
1343 The current value of ESP (stack pointer), as found in
1344 the kernel stack page for the process.
1345 (30) kstkeip %lu [PT]
1347 The current EIP (instruction pointer).
1348 (31) signal %lu
1350 The bitmap of pending signals, displayed as a decimal
1351 number. Obsolete, because it does not provide infor‐
1352 mation on real-time signals; use /proc/[pid]/status
1353 instead.
1354 (32) blocked %lu
1356 The bitmap of blocked signals, displayed as a decimal
1357 number. Obsolete, because it does not provide infor‐
1358 mation on real-time signals; use /proc/[pid]/status
1359 instead.
1360 (33) sigignore %lu
1362 The bitmap of ignored signals, displayed as a decimal
1363 number. Obsolete, because it does not provide infor‐
1364 mation on real-time signals; use /proc/[pid]/status
1365 instead.
1366 (34) sigcatch %lu
1368 The bitmap of caught signals, displayed as a decimal
1369 number. Obsolete, because it does not provide infor‐
1370 mation on real-time signals; use /proc/[pid]/status
1371 instead.
1372 (35) wchan %lu [PT]
1374 This is the "channel" in which the process is waiting.
1375 It is the address of a location in the kernel where
1376 the process is sleeping. The corresponding symbolic
1377 name can be found in /proc/[pid]/wchan.
1378 (36) nswap %lu
1380 Number of pages swapped (not maintained).
1381 (37) cnswap %lu
1383 Cumulative nswap for child processes (not maintained).
1384 (38) exit_signal %d (since Linux 2.1.22)
1386 Signal to be sent to parent when we die.
1387 (39) processor %d (since Linux 2.2.8)
1389 CPU number last executed on.
1390 (40) rt_priority %u (since Linux 2.5.19)
1392 Real-time scheduling priority, a number in the range 1
1393 to 99 for processes scheduled under a real-time pol‐
1394 icy, or 0, for non-real-time processes (see
1395 sched_setscheduler(2)).
1396 (41) policy %u (since Linux 2.5.19)
1398 Scheduling policy (see sched_setscheduler(2)). Decode
1399 using the SCHED_* constants in linux/sched.h.
1400 The format for this field was %lu before Linux 2.6.22.
1402 (42) delayacct_blkio_ticks %llu (since Linux 2.6.18)
1404 Aggregated block I/O delays, measured in clock ticks
1405 (centiseconds).
1406 (43) guest_time %lu (since Linux 2.6.24)
1408 Guest time of the process (time spent running a vir‐
1409 tual CPU for a guest operating system), measured in
1410 clock ticks (divide by sysconf(_SC_CLK_TCK)).
1411 (44) cguest_time %ld (since Linux 2.6.24)
1413 Guest time of the process's children, measured in
1414 clock ticks (divide by sysconf(_SC_CLK_TCK)).
1415 (45) start_data %lu (since Linux 3.3) [PT]
1417 Address above which program initialized and uninitial‐
1418 ized (BSS) data are placed.
1419 (46) end_data %lu (since Linux 3.3) [PT]
1421 Address below which program initialized and uninitial‐
1422 ized (BSS) data are placed.
1423 (47) start_brk %lu (since Linux 3.3) [PT]
1425 Address above which program heap can be expanded with
1426 brk(2).
1427 (48) arg_start %lu (since Linux 3.5) [PT]
1429 Address above which program command-line arguments
1430 (argv) are placed.
1431 (49) arg_end %lu (since Linux 3.5) [PT]
1433 Address below program command-line arguments (argv)
1434 are placed.
1435 (50) env_start %lu (since Linux 3.5) [PT]
1437 Address above which program environment is placed.
1438 (51) env_end %lu (since Linux 3.5) [PT]
1440 Address below which program environment is placed.
1441 (52) exit_code %d (since Linux 3.5) [PT]
1443 The thread's exit status in the form reported by wait‐
1444 pid(2).
1445 /proc/[pid]/statm
1447 Provides information about memory usage, measured in pages. The
1448 columns are:
1449 size (1) total program size
1451 (same as VmSize in /proc/[pid]/status)
1452 resident (2) resident set size
1453 (same as VmRSS in /proc/[pid]/status)
1454 shared (3) number of resident shared pages (i.e., backed by a file)
1455 (same as RssFile+RssShmem in /proc/[pid]/status)
1456 text (4) text (code)
1457 lib (5) library (unused since Linux 2.6; always 0)
1458 data (6) data + stack
1459 dt (7) dirty pages (unused since Linux 2.6; always 0)
1460 /proc/[pid]/status
1462 Provides much of the information in /proc/[pid]/stat and
1463 /proc/[pid]/statm in a format that's easier for humans to parse.
1464 Here's an example:
1465 $ cat /proc/$$/status
1467 Name: bash
1468 Umask: 0022
1469 State: S (sleeping)
1470 Tgid: 17248
1471 Ngid: 0
1472 Pid: 17248
1473 PPid: 17200
1474 TracerPid: 0
1475 Uid: 1000 1000 1000 1000
1476 Gid: 100 100 100 100
1477 FDSize: 256
1478 Groups: 16 33 100
1479 NStgid: 17248
1480 NSpid: 17248
1481 NSpgid: 17248
1482 NSsid: 17200
1483 VmPeak: 131168 kB
1484 VmSize: 131168 kB
1485 VmLck: 0 kB
1486 VmPin: 0 kB
1487 VmHWM: 13484 kB
1488 VmRSS: 13484 kB
1489 RssAnon: 10264 kB
1490 RssFile: 3220 kB
1491 RssShmem: 0 kB
1492 VmData: 10332 kB
1493 VmStk: 136 kB
1494 VmExe: 992 kB
1495 VmLib: 2104 kB
1496 VmPTE: 76 kB
1497 VmPMD: 12 kB
1498 VmSwap: 0 kB
1499 HugetlbPages: 0 kB # 4.4
1500 Threads: 1
1501 SigQ: 0/3067
1502 SigPnd: 0000000000000000
1503 ShdPnd: 0000000000000000
1504 SigBlk: 0000000000010000
1505 SigIgn: 0000000000384004
1506 SigCgt: 000000004b813efb
1507 CapInh: 0000000000000000
1508 CapPrm: 0000000000000000
1509 CapEff: 0000000000000000
1510 CapBnd: ffffffffffffffff
1511 CapAmb: 0000000000000000
1512 NoNewPrivs: 0
1513 Seccomp: 0
1514 Speculation_Store_Bypass: vulnerable
1515 Cpus_allowed: 00000001
1516 Cpus_allowed_list: 0
1517 Mems_allowed: 1
1518 Mems_allowed_list: 0
1519 voluntary_ctxt_switches: 150
1520 nonvoluntary_ctxt_switches: 545
1521 The fields are as follows:
1523 * Name: Command run by this process.
1525 * Umask: Process umask, expressed in octal with a leading zero;
1527 see umask(2). (Since Linux 4.7.)
1528 * State: Current state of the process. One of "R (running)", "S
1530 (sleeping)", "D (disk sleep)", "T (stopped)", "T (tracing
1531 stop)", "Z (zombie)", or "X (dead)".
1532 * Tgid: Thread group ID (i.e., Process ID).
1534 * Ngid: NUMA group ID (0 if none; since Linux 3.13).
1536 * Pid: Thread ID (see gettid(2)).
1538 * PPid: PID of parent process.
1540 * TracerPid: PID of process tracing this process (0 if not being
1542 traced).
1543 * Uid, Gid: Real, effective, saved set, and filesystem UIDs
1545 (GIDs).
1546 * FDSize: Number of file descriptor slots currently allocated.
1548 * Groups: Supplementary group list.
1550 * NStgid : Thread group ID (i.e., PID) in each of the PID names‐
1552 paces of which [pid] is a member. The leftmost entry shows
1553 the value with respect to the PID namespace of the reading
1554 process, followed by the value in successively nested inner
1555 namespaces. (Since Linux 4.1.)
1556 * NSpid: Thread ID in each of the PID namespaces of which [pid]
1558 is a member. The fields are ordered as for NStgid. (Since
1559 Linux 4.1.)
1560 * NSpgid: Process group ID in each of the PID namespaces of
1562 which [pid] is a member. The fields are ordered as for NSt‐
1563 gid. (Since Linux 4.1.)
1564 * NSsid: descendant namespace session ID hierarchy Session ID in
1566 each of the PID namespaces of which [pid] is a member. The
1567 fields are ordered as for NStgid. (Since Linux 4.1.)
1568 * VmPeak: Peak virtual memory size.
1570 * VmSize: Virtual memory size.
1572 * VmLck: Locked memory size (see mlock(3)).
1574 * VmPin: Pinned memory size (since Linux 3.2). These are pages
1576 that can't be moved because something needs to directly access
1577 physical memory.
1578 * VmHWM: Peak resident set size ("high water mark").
1580 * VmRSS: Resident set size. Note that the value here is the sum
1582 of RssAnon, RssFile, and RssShmem.
1583 * RssAnon: Size of resident anonymous memory. (since Linux
1585 4.5).
1586 * RssFile: Size of resident file mappings. (since Linux 4.5).
1588 * RssShmem: Size of resident shared memory (includes System V
1590 shared memory, mappings from tmpfs(5), and shared anonymous
1591 mappings). (since Linux 4.5).
1592 * VmData, VmStk, VmExe: Size of data, stack, and text segments.
1594 * VmLib: Shared library code size.
1596 * VmPTE: Page table entries size (since Linux 2.6.10).
1598 * VmPMD: Size of second-level page tables (since Linux 4.0).
1600 * VmSwap: Swapped-out virtual memory size by anonymous private
1602 pages; shmem swap usage is not included (since Linux 2.6.34).
1603 * HugetlbPages: Size of hugetlb memory portions. (since Linux
1605 4.4).
1606 * Threads: Number of threads in process containing this thread.
1608 * SigQ: This field contains two slash-separated numbers that
1610 relate to queued signals for the real user ID of this process.
1611 The first of these is the number of currently queued signals
1612 for this real user ID, and the second is the resource limit on
1613 the number of queued signals for this process (see the
1614 description of RLIMIT_SIGPENDING in getrlimit(2)).
1615 * SigPnd, ShdPnd: Number of signals pending for thread and for
1617 process as a whole (see pthreads(7) and signal(7)).
1618 * SigBlk, SigIgn, SigCgt: Masks indicating signals being
1620 blocked, ignored, and caught (see signal(7)).
1621 * CapInh, CapPrm, CapEff: Masks of capabilities enabled in
1623 inheritable, permitted, and effective sets (see capabili‐
1624 ties(7)).
1625 * CapBnd: Capability Bounding set (since Linux 2.6.26, see capa‐
1627 bilities(7)).
1628 * CapAmb: Ambient capability set (since Linux 4.3, see capabili‐
1630 ties(7)).
1631 * NoNewPrivs: Value of the no_new_privs bit (since Linux 4.10,
1633 see prctl(2)).
1634 * Seccomp: Seccomp mode of the process (since Linux 3.8, see
1636 seccomp(2)). 0 means SECCOMP_MODE_DISABLED; 1 means SEC‐
1637 COMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER. This field is
1638 provided only if the kernel was built with the CONFIG_SECCOMP
1639 kernel configuration option enabled.
1640 * Speculation_Store_Bypass: Speculation flaw mitigation state
1642 (since Linux 4.17, see prctl(2)).
1643 * Cpus_allowed: Mask of CPUs on which this process may run
1645 (since Linux 2.6.24, see cpuset(7)).
1646 * Cpus_allowed_list: Same as previous, but in "list format"
1648 (since Linux 2.6.26, see cpuset(7)).
1649 * Mems_allowed: Mask of memory nodes allowed to this process
1651 (since Linux 2.6.24, see cpuset(7)).
1652 * Mems_allowed_list: Same as previous, but in "list format"
1654 (since Linux 2.6.26, see cpuset(7)).
1655 * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of
1657 voluntary and involuntary context switches (since Linux
1658 2.6.23).
1659 /proc/[pid]/syscall (since Linux 2.6.27)
1661 This file exposes the system call number and argument registers
1662 for the system call currently being executed by the process,
1663 followed by the values of the stack pointer and program counter
1664 registers. The values of all six argument registers are
1665 exposed, although most system calls use fewer registers.
1666 If the process is blocked, but not in a system call, then the
1668 file displays -1 in place of the system call number, followed by
1669 just the values of the stack pointer and program counter. If
1670 process is not blocked, then the file contains just the string
1671 "running".
1672 This file is present only if the kernel was configured with CON‐
1674 FIG_HAVE_ARCH_TRACEHOOK.
1675 Permission to access this file is governed by a ptrace access
1677 mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).
1678 /proc/[pid]/task (since Linux 2.6.0-test6)
1680 This is a directory that contains one subdirectory for each
1681 thread in the process. The name of each subdirectory is the
1682 numerical thread ID ([tid]) of the thread (see gettid(2)).
1683 Within each of these subdirectories, there is a set of files
1684 with the same names and contents as under the /proc/[pid] direc‐
1685 tories. For attributes that are shared by all threads, the con‐
1686 tents for each of the files under the task/[tid] subdirectories
1687 will be the same as in the corresponding file in the parent
1688 /proc/[pid] directory (e.g., in a multithreaded process, all of
1689 the task/[tid]/cwd files will have the same value as the
1690 /proc/[pid]/cwd file in the parent directory, since all of the
1691 threads in a process share a working directory). For attributes
1692 that are distinct for each thread, the corresponding files under
1693 task/[tid] may have different values (e.g., various fields in
1694 each of the task/[tid]/status files may be different for each
1695 thread), or they might not exist in /proc/[pid] at all. In a
1696 multithreaded process, the contents of the /proc/[pid]/task
1697 directory are not available if the main thread has already ter‐
1698 minated (typically by calling pthread_exit(3)).
1699 /proc/[pid]/task/[tid]/children (since Linux 3.5)
1701 A space-separated list of child tasks of this task. Each child
1702 task is represented by its TID.
1703 This option is intended for use by the checkpoint-restore (CRIU)
1705 system, and reliably provides a list of children only if all of
1706 the child processes are stopped or frozen. It does not work
1707 properly if children of the target task exit while the file is
1708 being read! Exiting children may cause non-exiting children to
1709 be omitted from the list. This makes this interface even more
1710 unreliable than classic PID-based approaches if the inspected
1711 task and its children aren't frozen, and most code should proba‐
1712 bly not use this interface.
1713 Until Linux 4.2, the presence of this file was governed by the
1715 CONFIG_CHECKPOINT_RESTORE kernel configuration option. Since
1716 Linux 4.2, it is governed by the CONFIG_PROC_CHILDREN option.
1717 /proc/[pid]/timers (since Linux 3.10)
1719 A list of the POSIX timers for this process. Each timer is
1720 listed with a line that starts with the string "ID:". For exam‐
1721 ple:
1722 ID: 1
1724 signal: 60/00007fff86e452a8
1725 notify: signal/pid.2634
1726 ClockID: 0
1727 ID: 0
1728 signal: 60/00007fff86e452a8
1729 notify: signal/pid.2634
1730 ClockID: 1
1731 The lines shown for each timer have the following meanings:
1733 ID The ID for this timer. This is not the same as the timer
1735 ID returned by timer_create(2); rather, it is the same
1736 kernel-internal ID that is available via the si_timerid
1737 field of the siginfo_t structure (see sigaction(2)).
1738 signal This is the signal number that this timer uses to deliver
1740 notifications followed by a slash, and then the
1741 sigev_value value supplied to the signal handler. Valid
1742 only for timers that notify via a signal.
1743 notify The part before the slash specifies the mechanism that
1745 this timer uses to deliver notifications, and is one of
1746 "thread", "signal", or "none". Immediately following the
1747 slash is either the string "tid" for timers with
1748 SIGEV_THREAD_ID notification, or "pid" for timers that
1749 notify by other mechanisms. Following the "." is the PID
1750 of the process (or the kernel thread ID of the thread)
1751 that will be delivered a signal if the timer delivers
1752 notifications via a signal.
1753 ClockID
1755 This field identifies the clock that the timer uses for
1756 measuring time. For most clocks, this is a number that
1757 matches one of the user-space CLOCK_* constants exposed
1758 via <time.h>. CLOCK_PROCESS_CPUTIME_ID timers display
1759 with a value of -6 in this field.
1760 CLOCK_THREAD_CPUTIME_ID timers display with a value of -2
1761 in this field.
1762 This file is available only when the kernel was configured with
1764 CONFIG_CHECKPOINT_RESTORE.
1765 /proc/[pid]/timerslack_ns (since Linux 4.6)
1767 This file exposes the process's "current" timer slack value,
1768 expressed in nanoseconds. The file is writable, allowing the
1769 process's timer slack value to be changed. Writing 0 to this
1770 file resets the "current" timer slack to the "default" timer
1771 slack value. For further details, see the discussion of
1772 PR_SET_TIMERSLACK in prctl(2).
1773 Initially, permission to access this file was governed by a
1775 ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check (see
1776 ptrace(2)). However, this was subsequently deemed too strict a
1777 requirement (and had the side effect that requiring a process to
1778 have the CAP_SYS_PTRACE capability would also allow it to view
1779 and change any process's memory). Therefore, since Linux 4.9,
1780 only the (weaker) CAP_SYS_NICE capability is required to access
1781 this file.
1782 /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)
1784 See user_namespaces(7).
1785 /proc/[pid]/wchan (since Linux 2.6.0)
1787 The symbolic name corresponding to the location in the kernel
1788 where the process is sleeping.
1789 Permission to access this file is governed by a ptrace access
1791 mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
1792 /proc/apm
1794 Advanced power management version and battery information when
1795 CONFIG_APM is defined at kernel compilation time.
1796 /proc/buddyinfo
1798 This file contains information which is used for diagnosing mem‐
1799 ory fragmentation issues. Each line starts with the identifica‐
1800 tion of the node and the name of the zone which together iden‐
1801 tify a memory region This is then followed by the count of
1802 available chunks of a certain order in which these zones are
1803 split. The size in bytes of a certain order is given by the
1804 formula:
1805 (2^order) * PAGE_SIZE
1807 The binary buddy allocator algorithm inside the kernel will
1809 split one chunk into two chunks of a smaller order (thus with
1810 half the size) or combine two contiguous chunks into one larger
1811 chunk of a higher order (thus with double the size) to satisfy
1812 allocation requests and to counter memory fragmentation. The
1813 order matches the column number, when starting to count at zero.
1814 For example on an x86-64 system:
1816 Node 0, zone DMA 1 1 1 0 2 1 1 0 1 1 3
1818 Node 0, zone DMA32 65 47 4 81 52 28 13 10 5 1 404
1819 Node 0, zone Normal 216 55 189 101 84 38 37 27 5 3 587
1820 In this example, there is one node containing three zones and
1822 there are 11 different chunk sizes. If the page size is 4 kilo‐
1823 bytes, then the first zone called DMA (on x86 the first 16
1824 megabyte of memory) has 1 chunk of 4 kilobytes (order 0) avail‐
1825 able and has 3 chunks of 4 megabytes (order 10) available.
1826 If the memory is heavily fragmented, the counters for higher
1828 order chunks will be zero and allocation of large contiguous
1829 areas will fail.
1830 Further information about the zones can be found in /proc/zone‐
1832 info.
1833 /proc/bus
1835 Contains subdirectories for installed busses.
1836 /proc/bus/pccard
1838 Subdirectory for PCMCIA devices when CONFIG_PCMCIA is set at
1839 kernel compilation time.
1840 /proc/bus/pccard/drivers
1842 /proc/bus/pci
1844 Contains various bus subdirectories and pseudo-files containing
1845 information about PCI busses, installed devices, and device
1846 drivers. Some of these files are not ASCII.
1847 /proc/bus/pci/devices
1849 Information about PCI devices. They may be accessed through
1850 lspci(8) and setpci(8).
1851 /proc/cgroups (since Linux 2.6.24)
1853 See cgroups(7).
1854 /proc/cmdline
1856 Arguments passed to the Linux kernel at boot time. Often done
1857 via a boot manager such as lilo(8) or grub(8).
1858 /proc/config.gz (since Linux 2.6)
1860 This file exposes the configuration options that were used to
1861 build the currently running kernel, in the same format as they
1862 would be shown in the .config file that resulted when configur‐
1863 ing the kernel (using make xconfig, make config, or similar).
1864 The file contents are compressed; view or search them using
1865 zcat(1) and zgrep(1). As long as no changes have been made to
1866 the following file, the contents of /proc/config.gz are the same
1867 as those provided by:
1868 cat /lib/modules/$(uname -r)/build/.config
1870 /proc/config.gz is provided only if the kernel is configured
1872 with CONFIG_IKCONFIG_PROC.
1873 /proc/crypto
1875 A list of the ciphers provided by the kernel crypto API. For
1876 details, see the kernel Linux Kernel Crypto API documentation
1877 available under the kernel source directory Documenta‐
1878 tion/crypto/ (or Documentation/DocBook before 4.10; the documen‐
1879 tation can be built using a command such as make htmldocs in the
1880 root directory of the kernel source tree).
1881 /proc/cpuinfo
1883 This is a collection of CPU and system architecture dependent
1884 items, for each supported architecture a different list. Two
1885 common entries are processor which gives CPU number and
1886 bogomips; a system constant that is calculated during kernel
1887 initialization. SMP machines have information for each CPU.
1888 The lscpu(1) command gathers its information from this file.
1889 /proc/devices
1891 Text listing of major numbers and device groups. This can be
1892 used by MAKEDEV scripts for consistency with the kernel.
1893 /proc/diskstats (since Linux 2.5.69)
1895 This file contains disk I/O statistics for each disk device.
1896 See the Linux kernel source file Documentation/iostats.txt for
1897 further information.
1898 /proc/dma
1900 This is a list of the registered ISA DMA (direct memory access)
1901 channels in use.
1902 /proc/driver
1904 Empty subdirectory.
1905 /proc/execdomains
1907 List of the execution domains (ABI personalities).
1908 /proc/fb
1910 Frame buffer information when CONFIG_FB is defined during kernel
1911 compilation.
1912 /proc/filesystems
1914 A text listing of the filesystems which are supported by the
1915 kernel, namely filesystems which were compiled into the kernel
1916 or whose kernel modules are currently loaded. (See also
1917 filesystems(5).) If a filesystem is marked with "nodev", this
1918 means that it does not require a block device to be mounted
1919 (e.g., virtual filesystem, network filesystem).
1920 Incidentally, this file may be used by mount(8) when no filesys‐
1922 tem is specified and it didn't manage to determine the filesys‐
1923 tem type. Then filesystems contained in this file are tried
1924 (excepted those that are marked with "nodev").
1925 /proc/fs
1927 Contains subdirectories that in turn contain files with informa‐
1928 tion about (certain) mounted filesystems.
1929 /proc/ide
1931 This directory exists on systems with the IDE bus. There are
1932 directories for each IDE channel and attached device. Files
1933 include:
1934 cache buffer size in KB
1936 capacity number of sectors
1937 driver driver version
1938 geometry physical and logical geometry
1939 identify in hexadecimal
1940 media media type
1941 model manufacturer's model number
1942 settings drive settings
1943 smart_thresholds in hexadecimal
1944 smart_values in hexadecimal
1945 The hdparm(8) utility provides access to this information in a
1947 friendly format.
1948 /proc/interrupts
1950 This is used to record the number of interrupts per CPU per IO
1951 device. Since Linux 2.6.24, for the i386 and x86-64 architec‐
1952 tures, at least, this also includes interrupts internal to the
1953 system (that is, not associated with a device as such), such as
1954 NMI (nonmaskable interrupt), LOC (local timer interrupt), and
1955 for SMP systems, TLB (TLB flush interrupt), RES (rescheduling
1956 interrupt), CAL (remote function call interrupt), and possibly
1957 others. Very easy to read formatting, done in ASCII.
1958 /proc/iomem
1960 I/O memory map in Linux 2.4.
1961 /proc/ioports
1963 This is a list of currently registered Input-Output port regions
1964 that are in use.
1965 /proc/kallsyms (since Linux 2.5.71)
1967 This holds the kernel exported symbol definitions used by the
1968 modules(X) tools to dynamically link and bind loadable modules.
1969 In Linux 2.5.47 and earlier, a similar file with slightly dif‐
1970 ferent syntax was named ksyms.
1971 /proc/kcore
1973 This file represents the physical memory of the system and is
1974 stored in the ELF core file format. With this pseudo-file, and
1975 an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
1976 used to examine the current state of any kernel data structures.
1977 The total length of the file is the size of physical memory
1979 (RAM) plus 4 KiB.
1980 /proc/keys (since Linux 2.6.10)
1982 See keyrings(7).
1983 /proc/key-users (since Linux 2.6.10)
1985 See keyrings(7).
1986 /proc/kmsg
1988 This file can be used instead of the syslog(2) system call to
1989 read kernel messages. A process must have superuser privileges
1990 to read this file, and only one process should read this file.
1991 This file should not be read if a syslog process is running
1992 which uses the syslog(2) system call facility to log kernel mes‐
1993 sages.
1994 Information in this file is retrieved with the dmesg(1) program.
1996 /proc/kpagecgroup (since Linux 4.3)
1998 This file contains a 64-bit inode number of the memory cgroup
1999 each page is charged to, indexed by page frame number (see the
2000 discussion of /proc/[pid]/pagemap).
2001 The /proc/kpagecgroup file is present only if the CONFIG_MEMCG
2003 kernel configuration option is enabled.
2004 /proc/kpagecount (since Linux 2.6.25)
2006 This file contains a 64-bit count of the number of times each
2007 physical page frame is mapped, indexed by page frame number (see
2008 the discussion of /proc/[pid]/pagemap).
2009 The /proc/kpagecount file is present only if the CON‐
2011 FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
2012 /proc/kpageflags (since Linux 2.6.25)
2014 This file contains 64-bit masks corresponding to each physical
2015 page frame; it is indexed by page frame number (see the discus‐
2016 sion of /proc/[pid]/pagemap). The bits are as follows:
2017 0 - KPF_LOCKED
2019 1 - KPF_ERROR
2020 2 - KPF_REFERENCED
2021 3 - KPF_UPTODATE
2022 4 - KPF_DIRTY
2023 5 - KPF_LRU
2024 6 - KPF_ACTIVE
2025 7 - KPF_SLAB
2026 8 - KPF_WRITEBACK
2027 9 - KPF_RECLAIM
2028 10 - KPF_BUDDY
2029 11 - KPF_MMAP (since Linux 2.6.31)
2030 12 - KPF_ANON (since Linux 2.6.31)
2031 13 - KPF_SWAPCACHE (since Linux 2.6.31)
2032 14 - KPF_SWAPBACKED (since Linux 2.6.31)
2033 15 - KPF_COMPOUND_HEAD (since Linux 2.6.31)
2034 16 - KPF_COMPOUND_TAIL (since Linux 2.6.31)
2035 17 - KPF_HUGE (since Linux 2.6.31)
2036 18 - KPF_UNEVICTABLE (since Linux 2.6.31)
2037 19 - KPF_HWPOISON (since Linux 2.6.31)
2038 20 - KPF_NOPAGE (since Linux 2.6.31)
2039 21 - KPF_KSM (since Linux 2.6.32)
2040 22 - KPF_THP (since Linux 3.4)
2041 23 - KPF_BALLOON (since Linux 3.18)
2042 24 - KPF_ZERO_PAGE (since Linux 4.0)
2043 25 - KPF_IDLE (since Linux 4.3)
2044 For further details on the meanings of these bits, see the ker‐
2046 nel source file Documentation/vm/pagemap.txt. Before kernel
2047 2.6.29, KPF_WRITEBACK, KPF_RECLAIM, KPF_BUDDY, and KPF_LOCKED
2048 did not report correctly.
2049 The /proc/kpageflags file is present only if the CON‐
2051 FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
2052 /proc/ksyms (Linux 1.1.23–2.5.47)
2054 See /proc/kallsyms.
2055 /proc/loadavg
2057 The first three fields in this file are load average figures
2058 giving the number of jobs in the run queue (state R) or waiting
2059 for disk I/O (state D) averaged over 1, 5, and 15 minutes. They
2060 are the same as the load average numbers given by uptime(1) and
2061 other programs. The fourth field consists of two numbers sepa‐
2062 rated by a slash (/). The first of these is the number of cur‐
2063 rently runnable kernel scheduling entities (processes, threads).
2064 The value after the slash is the number of kernel scheduling
2065 entities that currently exist on the system. The fifth field is
2066 the PID of the process that was most recently created on the
2067 system.
2068 /proc/locks
2070 This file shows current file locks (flock(2) and fcntl(2)) and
2071 leases (fcntl(2)).
2072 An example of the content shown in this file is the following:
2074 1: POSIX ADVISORY READ 5433 08:01:7864448 128 128
2076 2: FLOCK ADVISORY WRITE 2001 08:01:7864554 0 EOF
2077 3: FLOCK ADVISORY WRITE 1568 00:2f:32388 0 EOF
2078 4: POSIX ADVISORY WRITE 699 00:16:28457 0 EOF
2079 5: POSIX ADVISORY WRITE 764 00:16:21448 0 0
2080 6: POSIX ADVISORY READ 3548 08:01:7867240 1 1
2081 7: POSIX ADVISORY READ 3548 08:01:7865567 1826 2335
2082 8: OFDLCK ADVISORY WRITE -1 08:01:8713209 128 191
2083 The fields shown in each line are as follows:
2085 (1) The ordinal position of the lock in the list.
2087 (2) The lock type. Values that may appear here include:
2089 FLOCK This is a BSD file lock created using flock(2).
2091 OFDLCK This is an open file description (OFD) lock created
2093 using fcntl(2).
2094 POSIX This is a POSIX byte-range lock created using
2096 fcntl(2).
2097 (3) Among the strings that can appear here are the following:
2099 ADVISORY
2101 This is an advisory lock.
2102 MANDATORY
2104 This is a mandatory lock.
2105 (4) The type of lock. Values that can appear here are:
2107 READ This is a POSIX or OFD read lock, or a BSD shared
2109 lock.
2110 WRITE This is a POSIX or OFD write lock, or a BSD exclusive
2112 lock.
2113 (5) The PID of the process that owns the lock.
2115 Because OFD locks are not owned by a single process (since
2117 multiple processes may have file descriptors that refer to
2118 the same open file description), the value -1 is displayed
2119 in this field for OFD locks. (Before kernel 4.14, a bug
2120 meant that the PID of the process that initially acquired
2121 the lock was displayed instead of the value -1.)
2122 (6) Three colon-separated subfields that identify the major and
2124 minor device ID of the device containing the filesystem
2125 where the locked file resides, followed by the inode number
2126 of the locked file.
2127 (7) The byte offset of the first byte of the lock. For BSD
2129 locks, this value is always 0.
2130 (8) The byte offset of the last byte of the lock. EOF in this
2132 field means that the lock extends to the end of the file.
2133 For BSD locks, the value shown is always EOF.
2134 Since Linux 4.9, the list of locks shown in /proc/locks is fil‐
2136 tered to show just the locks for the processes in the PID names‐
2137 pace (see pid_namespaces(7)) for which the /proc filesystem was
2138 mounted. (In the initial PID namespace, there is no filtering
2139 of the records shown in this file.)
2140 The lslocks(8) command provides a bit more information about
2142 each lock.
2143 /proc/malloc (only up to and including Linux 2.2)
2145 This file is present only if CONFIG_DEBUG_MALLOC was defined
2146 during compilation.
2147 /proc/meminfo
2149 This file reports statistics about memory usage on the system.
2150 It is used by free(1) to report the amount of free and used mem‐
2151 ory (both physical and swap) on the system as well as the shared
2152 memory and buffers used by the kernel. Each line of the file
2153 consists of a parameter name, followed by a colon, the value of
2154 the parameter, and an option unit of measurement (e.g., "kB").
2155 The list below describes the parameter names and the format
2156 specifier required to read the field value. Except as noted
2157 below, all of the fields have been present since at least Linux
2158 2.6.0. Some fields are displayed only if the kernel was config‐
2159 ured with various options; those dependencies are noted in the
2160 list.
2161 MemTotal %lu
2163 Total usable RAM (i.e., physical RAM minus a few reserved
2164 bits and the kernel binary code).
2165 MemFree %lu
2167 The sum of LowFree+HighFree.
2168 MemAvailable %lu (since Linux 3.14)
2170 An estimate of how much memory is available for starting
2171 new applications, without swapping.
2172 Buffers %lu
2174 Relatively temporary storage for raw disk blocks that
2175 shouldn't get tremendously large (20MB or so).
2176 Cached %lu
2178 In-memory cache for files read from the disk (the page
2179 cache). Doesn't include SwapCached.
2180 SwapCached %lu
2182 Memory that once was swapped out, is swapped back in but
2183 still also is in the swap file. (If memory pressure is
2184 high, these pages don't need to be swapped out again
2185 because they are already in the swap file. This saves
2186 I/O.)
2187 Active %lu
2189 Memory that has been used more recently and usually not
2190 reclaimed unless absolutely necessary.
2191 Inactive %lu
2193 Memory which has been less recently used. It is more
2194 eligible to be reclaimed for other purposes.
2195 Active(anon) %lu (since Linux 2.6.28)
2197 [To be documented.]
2198 Inactive(anon) %lu (since Linux 2.6.28)
2200 [To be documented.]
2201 Active(file) %lu (since Linux 2.6.28)
2203 [To be documented.]
2204 Inactive(file) %lu (since Linux 2.6.28)
2206 [To be documented.]
2207 Unevictable %lu (since Linux 2.6.28)
2209 (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
2210 required.) [To be documented.]
2211 Mlocked %lu (since Linux 2.6.28)
2213 (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
2214 required.) [To be documented.]
2215 HighTotal %lu
2217 (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
2218 Total amount of highmem. Highmem is all memory above
2219 ~860MB of physical memory. Highmem areas are for use by
2220 user-space programs, or for the page cache. The kernel
2221 must use tricks to access this memory, making it slower
2222 to access than lowmem.
2223 HighFree %lu
2225 (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
2226 Amount of free highmem.
2227 LowTotal %lu
2229 (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
2230 Total amount of lowmem. Lowmem is memory which can be
2231 used for everything that highmem can be used for, but it
2232 is also available for the kernel's use for its own data
2233 structures. Among many other things, it is where every‐
2234 thing from Slab is allocated. Bad things happen when
2235 you're out of lowmem.
2236 LowFree %lu
2238 (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
2239 Amount of free lowmem.
2240 MmapCopy %lu (since Linux 2.6.29)
2242 (CONFIG_MMU is required.) [To be documented.]
2243 SwapTotal %lu
2245 Total amount of swap space available.
2246 SwapFree %lu
2248 Amount of swap space that is currently unused.
2249 Dirty %lu
2251 Memory which is waiting to get written back to the disk.
2252 Writeback %lu
2254 Memory which is actively being written back to the disk.
2255 AnonPages %lu (since Linux 2.6.18)
2257 Non-file backed pages mapped into user-space page tables.
2258 Mapped %lu
2260 Files which have been mapped into memory (with mmap(2)),
2261 such as libraries.
2262 Shmem %lu (since Linux 2.6.32)
2264 Amount of memory consumed in tmpfs(5) filesystems.
2265 Slab %lu
2267 In-kernel data structures cache. (See slabinfo(5).)
2268 SReclaimable %lu (since Linux 2.6.19)
2270 Part of Slab, that might be reclaimed, such as caches.
2271 SUnreclaim %lu (since Linux 2.6.19)
2273 Part of Slab, that cannot be reclaimed on memory pres‐
2274 sure.
2275 KernelStack %lu (since Linux 2.6.32)
2277 Amount of memory allocated to kernel stacks.
2278 PageTables %lu (since Linux 2.6.18)
2280 Amount of memory dedicated to the lowest level of page
2281 tables.
2282 Quicklists %lu (since Linux 2.6.27)
2284 (CONFIG_QUICKLIST is required.) [To be documented.]
2285 NFS_Unstable %lu (since Linux 2.6.18)
2287 NFS pages sent to the server, but not yet committed to
2288 stable storage.
2289 Bounce %lu (since Linux 2.6.18)
2291 Memory used for block device "bounce buffers".
2292 WritebackTmp %lu (since Linux 2.6.26)
2294 Memory used by FUSE for temporary writeback buffers.
2295 CommitLimit %lu (since Linux 2.6.10)
2297 This is the total amount of memory currently available to
2298 be allocated on the system, expressed in kilobytes. This
2299 limit is adhered to only if strict overcommit accounting
2300 is enabled (mode 2 in /proc/sys/vm/overcommit_memory).
2301 The limit is calculated according to the formula
2302 described under /proc/sys/vm/overcommit_memory. For fur‐
2303 ther details, see the kernel source file Documenta‐
2304 tion/vm/overcommit-accounting.
2305 Committed_AS %lu
2307 The amount of memory presently allocated on the system.
2308 The committed memory is a sum of all of the memory which
2309 has been allocated by processes, even if it has not been
2310 "used" by them as of yet. A process which allocates 1GB
2311 of memory (using malloc(3) or similar), but touches only
2312 300MB of that memory will show up as using only 300MB of
2313 memory even if it has the address space allocated for the
2314 entire 1GB.
2315 This 1GB is memory which has been "committed" to by the
2317 VM and can be used at any time by the allocating applica‐
2318 tion. With strict overcommit enabled on the system (mode
2319 2 in /proc/sys/vm/overcommit_memory), allocations which
2320 would exceed the CommitLimit will not be permitted. This
2321 is useful if one needs to guarantee that processes will
2322 not fail due to lack of memory once that memory has been
2323 successfully allocated.
2324 VmallocTotal %lu
2326 Total size of vmalloc memory area.
2327 VmallocUsed %lu
2329 Amount of vmalloc area which is used.
2330 VmallocChunk %lu
2332 Largest contiguous block of vmalloc area which is free.
2333 HardwareCorrupted %lu (since Linux 2.6.32)
2335 (CONFIG_MEMORY_FAILURE is required.) [To be documented.]
2336 AnonHugePages %lu (since Linux 2.6.38)
2338 (CONFIG_TRANSPARENT_HUGEPAGE is required.) Non-file
2339 backed huge pages mapped into user-space page tables.
2340 ShmemHugePages %lu (since Linux 4.8)
2342 (CONFIG_TRANSPARENT_HUGEPAGE is required.) Memory used
2343 by shared memory (shmem) and tmpfs(5) allocated with huge
2344 pages
2345 ShmemPmdMapped %lu (since Linux 4.8)
2347 (CONFIG_TRANSPARENT_HUGEPAGE is required.) Shared memory
2348 mapped into user space with huge pages.
2349 CmaTotal %lu (since Linux 3.1)
2351 Total CMA (Contiguous Memory Allocator) pages. (CON‐
2352 FIG_CMA is required.)
2353 CmaFree %lu (since Linux 3.1)
2355 Free CMA (Contiguous Memory Allocator) pages. (CON‐
2356 FIG_CMA is required.)
2357 HugePages_Total %lu
2359 (CONFIG_HUGETLB_PAGE is required.) The size of the pool
2360 of huge pages.
2361 HugePages_Free %lu
2363 (CONFIG_HUGETLB_PAGE is required.) The number of huge
2364 pages in the pool that are not yet allocated.
2365 HugePages_Rsvd %lu (since Linux 2.6.17)
2367 (CONFIG_HUGETLB_PAGE is required.) This is the number of
2368 huge pages for which a commitment to allocate from the
2369 pool has been made, but no allocation has yet been made.
2370 These reserved huge pages guarantee that an application
2371 will be able to allocate a huge page from the pool of
2372 huge pages at fault time.
2373 HugePages_Surp %lu (since Linux 2.6.24)
2375 (CONFIG_HUGETLB_PAGE is required.) This is the number of
2376 huge pages in the pool above the value in
2377 /proc/sys/vm/nr_hugepages. The maximum number of surplus
2378 huge pages is controlled by /proc/sys/vm/nr_overcom‐
2379 mit_hugepages.
2380 Hugepagesize %lu
2382 (CONFIG_HUGETLB_PAGE is required.) The size of huge
2383 pages.
2384 DirectMap4k %lu (since Linux 2.6.27)
2386 Number of bytes of RAM linearly mapped by kernel in 4kB
2387 pages. (x86.)
2388 DirectMap4M %lu (since Linux 2.6.27)
2390 Number of bytes of RAM linearly mapped by kernel in 4MB
2391 pages. (x86 with CONFIG_X86_64 or CONFIG_X86_PAE
2392 enabled.)
2393 DirectMap2M %lu (since Linux 2.6.27)
2395 Number of bytes of RAM linearly mapped by kernel in 2MB
2396 pages. (x86 with neither CONFIG_X86_64 nor CON‐
2397 FIG_X86_PAE enabled.)
2398 DirectMap1G %lu (since Linux 2.6.27)
2400 (x86 with CONFIG_X86_64 and CONFIG_X86_DIRECT_GBPAGES
2401 enabled.)
2402 /proc/modules
2404 A text list of the modules that have been loaded by the system.
2405 See also lsmod(8).
2406 /proc/mounts
2408 Before kernel 2.4.19, this file was a list of all the filesys‐
2409 tems currently mounted on the system. With the introduction of
2410 per-process mount namespaces in Linux 2.4.19 (see mount_names‐
2411 paces(7)), this file became a link to /proc/self/mounts, which
2412 lists the mount points of the process's own mount namespace.
2413 The format of this file is documented in fstab(5).
2414 /proc/mtrr
2416 Memory Type Range Registers. See the Linux kernel source file
2417 Documentation/x86/mtrr.txt (or Documentation/mtrr.txt before
2418 Linux 2.6.28) for details.
2419 /proc/net
2421 This directory contains various files and subdirectories con‐
2422 taining information about the networking layer. The files con‐
2423 tain ASCII structures and are, therefore, readable with cat(1).
2424 However, the standard netstat(8) suite provides much cleaner
2425 access to these files.
2426 With the advent of network namespaces, various information
2428 relating to the network stack is virtualized (see names‐
2429 paces(7)). Thus, since Linux 2.6.25, /proc/net is a symbolic
2430 link to the directory /proc/self/net, which contains the same
2431 files and directories as listed below. However, these files and
2432 directories now expose information for the network namespace of
2433 which the process is a member.
2434 /proc/net/arp
2436 This holds an ASCII readable dump of the kernel ARP table used
2437 for address resolutions. It will show both dynamically learned
2438 and preprogrammed ARP entries. The format is:
2439 IP address HW type Flags HW address Mask Device
2441 192.168.0.50 0x1 0x2 00:50:BF:25:68:F3 * eth0
2442 192.168.0.250 0x1 0xc 00:00:00:00:00:00 * eth0
2443 Here "IP address" is the IPv4 address of the machine and the "HW
2445 type" is the hardware type of the address from RFC 826. The
2446 flags are the internal flags of the ARP structure (as defined in
2447 /usr/include/linux/if_arp.h) and the "HW address" is the data
2448 link layer mapping for that IP address if it is known.
2449 /proc/net/dev
2451 The dev pseudo-file contains network device status information.
2452 This gives the number of received and sent packets, the number
2453 of errors and collisions and other basic statistics. These are
2454 used by the ifconfig(8) program to report device status. The
2455 format is:
2456 Inter-| Receive | Transmit
2458 face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
2459 lo: 2776770 11307 0 0 0 0 0 0 2776770 11307 0 0 0 0 0 0
2460 eth0: 1215645 2751 0 0 0 0 0 0 1782404 4324 0 0 0 427 0 0
2461 ppp0: 1622270 5552 1 0 0 0 0 0 354130 5669 0 0 0 0 0 0
2462 tap0: 7714 81 0 0 0 0 0 0 7714 81 0 0 0 0 0 0
2463 /proc/net/dev_mcast
2465 Defined in /usr/src/linux/net/core/dev_mcast.c:
2466 indx interface_name dmi_u dmi_g dmi_address
2468 2 eth0 1 0 01005e000001
2469 3 eth1 1 0 01005e000001
2470 4 eth2 1 0 01005e000001
2471 /proc/net/igmp
2473 Internet Group Management Protocol. Defined in
2474 /usr/src/linux/net/core/igmp.c.
2475 /proc/net/rarp
2477 This file uses the same format as the arp file and contains the
2478 current reverse mapping database used to provide rarp(8) reverse
2479 address lookup services. If RARP is not configured into the
2480 kernel, this file will not be present.
2481 /proc/net/raw
2483 Holds a dump of the RAW socket table. Much of the information
2484 is not of use apart from debugging. The "sl" value is the ker‐
2485 nel hash slot for the socket, the "local_address" is the local
2486 address and protocol number pair. "St" is the internal status
2487 of the socket. The "tx_queue" and "rx_queue" are the outgoing
2488 and incoming data queue in terms of kernel memory usage. The
2489 "tr", "tm->when", and "rexmits" fields are not used by RAW. The
2490 "uid" field holds the effective UID of the creator of the
2491 socket.
2492 /proc/net/snmp
2494 This file holds the ASCII data needed for the IP, ICMP, TCP, and
2495 UDP management information bases for an SNMP agent.
2496 /proc/net/tcp
2498 Holds a dump of the TCP socket table. Much of the information
2499 is not of use apart from debugging. The "sl" value is the ker‐
2500 nel hash slot for the socket, the "local_address" is the local
2501 address and port number pair. The "rem_address" is the remote
2502 address and port number pair (if connected). "St" is the inter‐
2503 nal status of the socket. The "tx_queue" and "rx_queue" are the
2504 outgoing and incoming data queue in terms of kernel memory
2505 usage. The "tr", "tm->when", and "rexmits" fields hold internal
2506 information of the kernel socket state and are useful only for
2507 debugging. The "uid" field holds the effective UID of the cre‐
2508 ator of the socket.
2509 /proc/net/udp
2511 Holds a dump of the UDP socket table. Much of the information
2512 is not of use apart from debugging. The "sl" value is the ker‐
2513 nel hash slot for the socket, the "local_address" is the local
2514 address and port number pair. The "rem_address" is the remote
2515 address and port number pair (if connected). "St" is the inter‐
2516 nal status of the socket. The "tx_queue" and "rx_queue" are the
2517 outgoing and incoming data queue in terms of kernel memory
2518 usage. The "tr", "tm->when", and "rexmits" fields are not used
2519 by UDP. The "uid" field holds the effective UID of the creator
2520 of the socket. The format is:
2521 sl local_address rem_address st tx_queue rx_queue tr rexmits tm->when uid
2523 1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
2524 1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
2525 1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0
2526 /proc/net/unix
2528 Lists the UNIX domain sockets present within the system and
2529 their status. The format is:
2530 Num RefCount Protocol Flags Type St Path
2532 0: 00000002 00000000 00000000 0001 03
2533 1: 00000001 00000000 00010000 0001 01 /dev/printer
2534 The fields are as follows:
2536 Num: the kernel table slot number.
2538 RefCount: the number of users of the socket.
2540 Protocol: currently always 0.
2542 Flags: the internal kernel flags holding the status of the
2544 socket.
2545 Type: the socket type. For SOCK_STREAM sockets, this is
2547 0001; for SOCK_DGRAM sockets, it is 0002; and for
2548 SOCK_SEQPACKET sockets, it is 0005.
2549 St: the internal state of the socket.
2551 Path: the bound path (if any) of the socket. Sockets in the
2553 abstract namespace are included in the list, and are
2554 shown with a Path that commences with the character
2555 '@'.
2556 /proc/net/netfilter/nfnetlink_queue
2558 This file contains information about netfilter user-space queue‐
2559 ing, if used. Each line represents a queue. Queues that have
2560 not been subscribed to by user space are not shown.
2561 1 4207 0 2 65535 0 0 0 1
2563 (1) (2) (3)(4) (5) (6) (7) (8)
2564 The fields in each line are:
2566 (1) The ID of the queue. This matches what is specified in the
2568 --queue-num or --queue-balance options to the iptables(8)
2569 NFQUEUE target. See iptables-extensions(8) for more infor‐
2570 mation.
2571 (2) The netlink port ID subscribed to the queue.
2573 (3) The number of packets currently queued and waiting to be
2575 processed by the application.
2576 (4) The copy mode of the queue. It is either 1 (metadata only)
2578 or 2 (also copy payload data to user space).
2579 (5) Copy range; that is, how many bytes of packet payload
2581 should be copied to user space at most.
2582 (6) queue dropped. Number of packets that had to be dropped by
2584 the kernel because too many packets are already waiting for
2585 user space to send back the mandatory accept/drop verdicts.
2586 (7) queue user dropped. Number of packets that were dropped
2588 within the netlink subsystem. Such drops usually happen
2589 when the corresponding socket buffer is full; that is, user
2590 space is not able to read messages fast enough.
2591 (8) sequence number. Every queued packet is associated with a
2593 (32-bit) monotonically-increasing sequence number. This
2594 shows the ID of the most recent packet queued.
2595 The last number exists only for compatibility reasons and is
2597 always 1.
2598 /proc/partitions
2600 Contains the major and minor numbers of each partition as well
2601 as the number of 1024-byte blocks and the partition name.
2602 /proc/pci
2604 This is a listing of all PCI devices found during kernel ini‐
2605 tialization and their configuration.
2606 This file has been deprecated in favor of a new /proc interface
2608 for PCI (/proc/bus/pci). It became optional in Linux 2.2
2609 (available with CONFIG_PCI_OLD_PROC set at kernel compilation).
2610 It became once more nonoptionally enabled in Linux 2.4. Next,
2611 it was deprecated in Linux 2.6 (still available with CON‐
2612 FIG_PCI_LEGACY_PROC set), and finally removed altogether since
2613 Linux 2.6.17.
2614 /proc/profile (since Linux 2.4)
2616 This file is present only if the kernel was booted with the pro‐
2617 file=1 command-line option. It exposes kernel profiling infor‐
2618 mation in a binary format for use by readprofile(1). Writing
2619 (e.g., an empty string) to this file resets the profiling coun‐
2620 ters; on some architectures, writing a binary integer "profiling
2621 multiplier" of size sizeof(int) sets the profiling interrupt
2622 frequency.
2623 /proc/scsi
2625 A directory with the scsi mid-level pseudo-file and various SCSI
2626 low-level driver directories, which contain a file for each SCSI
2627 host in this system, all of which give the status of some part
2628 of the SCSI IO subsystem. These files contain ASCII structures
2629 and are, therefore, readable with cat(1).
2630 You can also write to some of the files to reconfigure the sub‐
2632 system or switch certain features on or off.
2633 /proc/scsi/scsi
2635 This is a listing of all SCSI devices known to the kernel. The
2636 listing is similar to the one seen during bootup. scsi cur‐
2637 rently supports only the add-single-device command which allows
2638 root to add a hotplugged device to the list of known devices.
2639 The command
2641 echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi
2643 will cause host scsi1 to scan on SCSI channel 0 for a device on
2645 ID 5 LUN 0. If there is already a device known on this address
2646 or the address is invalid, an error will be returned.
2647 /proc/scsi/[drivername]
2649 [drivername] can currently be NCR53c7xx, aha152x, aha1542,
2650 aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
2651 pas16, qlogic, scsi_debug, seagate, t128, u15-24f, ultrastore,
2652 or wd7000. These directories show up for all drivers that reg‐
2653 istered at least one SCSI HBA. Every directory contains one
2654 file per registered host. Every host-file is named after the
2655 number the host was assigned during initialization.
2656 Reading these files will usually show driver and host configura‐
2658 tion, statistics, and so on.
2659 Writing to these files allows different things on different
2661 hosts. For example, with the latency and nolatency commands,
2662 root can switch on and off command latency measurement code in
2663 the eata_dma driver. With the lockup and unlock commands, root
2664 can control bus lockups simulated by the scsi_debug driver.
2665 /proc/self
2667 This directory refers to the process accessing the /proc
2668 filesystem, and is identical to the /proc directory named by the
2669 process ID of the same process.
2670 /proc/slabinfo
2672 Information about kernel caches. See slabinfo(5) for details.
2673 /proc/stat
2675 kernel/system statistics. Varies with architecture. Common
2676 entries include:
2677 cpu 10132153 290696 3084719 46828483 16683 0 25195 0 175628 0
2679 cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
2680 The amount of time, measured in units of USER_HZ
2681 (1/100ths of a second on most architectures, use
2682 sysconf(_SC_CLK_TCK) to obtain the right value), that the
2683 system ("cpu" line) or the specific CPU ("cpuN" line)
2684 spent in various states:
2685 user (1) Time spent in user mode.
2687 nice (2) Time spent in user mode with low priority
2689 (nice).
2690 system (3) Time spent in system mode.
2692 idle (4) Time spent in the idle task. This value
2694 should be USER_HZ times the second entry in the
2695 /proc/uptime pseudo-file.
2696 iowait (since Linux 2.5.41)
2698 (5) Time waiting for I/O to complete. This value
2699 is not reliable, for the following reasons:
2700 1. The CPU will not wait for I/O to complete;
2702 iowait is the time that a task is waiting for
2703 I/O to complete. When a CPU goes into idle
2704 state for outstanding task I/O, another task
2705 will be scheduled on this CPU.
2706 2. On a multi-core CPU, the task waiting for I/O
2708 to complete is not running on any CPU, so the
2709 iowait of each CPU is difficult to calculate.
2710 3. The value in this field may decrease in certain
2712 conditions.
2713 irq (since Linux 2.6.0-test4)
2715 (6) Time servicing interrupts.
2716 softirq (since Linux 2.6.0-test4)
2718 (7) Time servicing softirqs.
2719 steal (since Linux 2.6.11)
2721 (8) Stolen time, which is the time spent in other
2722 operating systems when running in a virtualized
2723 environment
2724 guest (since Linux 2.6.24)
2726 (9) Time spent running a virtual CPU for guest
2727 operating systems under the control of the Linux
2728 kernel.
2729 guest_nice (since Linux 2.6.33)
2731 (10) Time spent running a niced guest (virtual CPU
2732 for guest operating systems under the control of
2733 the Linux kernel).
2734 page 5741 1808
2736 The number of pages the system paged in and the number
2737 that were paged out (from disk).
2738 swap 1 0
2740 The number of swap pages that have been brought in and
2741 out.
2742 intr 1462898
2744 This line shows counts of interrupts serviced since boot
2745 time, for each of the possible system interrupts. The
2746 first column is the total of all interrupts serviced
2747 including unnumbered architecture specific interrupts;
2748 each subsequent column is the total for that particular
2749 numbered interrupt. Unnumbered interrupts are not shown,
2750 only summed into the total.
2751 disk_io: (2,0):(31,30,5764,1,2) (3,0):...
2753 (major,disk_idx):(noinfo, read_io_ops, blks_read,
2754 write_io_ops, blks_written)
2755 (Linux 2.4 only)
2756 ctxt 115315
2758 The number of context switches that the system underwent.
2759 btime 769041601
2761 boot time, in seconds since the Epoch, 1970-01-01
2762 00:00:00 +0000 (UTC).
2763 processes 86031
2765 Number of forks since boot.
2766 procs_running 6
2768 Number of processes in runnable state. (Linux 2.5.45
2769 onward.)
2770 procs_blocked 2
2772 Number of processes blocked waiting for I/O to complete.
2773 (Linux 2.5.45 onward.)
2774 softirq 229245889 94 60001584 13619 5175704 2471304 28 51212741
2776 59130143 0 51240672
2777 This line shows the number of softirq for all CPUs. The
2778 first column is the total of all softirqs and each subse‐
2779 quent column is the total for particular softirq. (Linux
2780 2.6.31 onward.)
2781 /proc/swaps
2783 Swap areas in use. See also swapon(8).
2784 /proc/sys
2786 This directory (present since 1.3.57) contains a number of files
2787 and subdirectories corresponding to kernel variables. These
2788 variables can be read and sometimes modified using the /proc
2789 filesystem, and the (deprecated) sysctl(2) system call.
2790 String values may be terminated by either '\0' or '\n'.
2792 Integer and long values may be written either in decimal or in
2794 hexadecimal notation (e.g. 0x3FFF). When writing multiple inte‐
2795 ger or long values, these may be separated by any of the follow‐
2796 ing whitespace characters: ' ', '\t', or '\n'. Using other sep‐
2797 arators leads to the error EINVAL.
2798 /proc/sys/abi (since Linux 2.4.10)
2800 This directory may contain files with application binary infor‐
2801 mation. See the Linux kernel source file Documenta‐
2802 tion/sysctl/abi.txt for more information.
2803 /proc/sys/debug
2805 This directory may be empty.
2806 /proc/sys/dev
2808 This directory contains device-specific information (e.g.,
2809 dev/cdrom/info). On some systems, it may be empty.
2810 /proc/sys/fs
2812 This directory contains the files and subdirectories for kernel
2813 variables related to filesystems.
2814 /proc/sys/fs/binfmt_misc
2816 Documentation for files in this directory can be found in the
2817 Linux kernel source in the file Documentation/admin-
2818 guide/binfmt-misc.rst (or in Documentation/binfmt_misc.txt on
2819 older kernels).
2820 /proc/sys/fs/dentry-state (since Linux 2.2)
2822 This file contains information about the status of the directory
2823 cache (dcache). The file contains six numbers, nr_dentry,
2824 nr_unused, age_limit (age in seconds), want_pages (pages
2825 requested by system) and two dummy values.
2826 * nr_dentry is the number of allocated dentries (dcache
2828 entries). This field is unused in Linux 2.2.
2829 * nr_unused is the number of unused dentries.
2831 * age_limit is the age in seconds after which dcache entries can
2833 be reclaimed when memory is short.
2834 * want_pages is nonzero when the kernel has called
2836 shrink_dcache_pages() and the dcache isn't pruned yet.
2837 /proc/sys/fs/dir-notify-enable
2839 This file can be used to disable or enable the dnotify interface
2840 described in fcntl(2) on a system-wide basis. A value of 0 in
2841 this file disables the interface, and a value of 1 enables it.
2842 /proc/sys/fs/dquot-max
2844 This file shows the maximum number of cached disk quota entries.
2845 On some (2.4) systems, it is not present. If the number of free
2846 cached disk quota entries is very low and you have some awesome
2847 number of simultaneous system users, you might want to raise the
2848 limit.
2849 /proc/sys/fs/dquot-nr
2851 This file shows the number of allocated disk quota entries and
2852 the number of free disk quota entries.
2853 /proc/sys/fs/epoll (since Linux 2.6.28)
2855 This directory contains the file max_user_watches, which can be
2856 used to limit the amount of kernel memory consumed by the epoll
2857 interface. For further details, see epoll(7).
2858 /proc/sys/fs/file-max
2860 This file defines a system-wide limit on the number of open
2861 files for all processes. System calls that fail when encounter‐
2862 ing this limit fail with the error ENFILE. (See also setr‐
2863 limit(2), which can be used by a process to set the per-process
2864 limit, RLIMIT_NOFILE, on the number of files it may open.) If
2865 you get lots of error messages in the kernel log about running
2866 out of file handles (look for "VFS: file-max limit <number>
2867 reached"), try increasing this value:
2868 echo 100000 > /proc/sys/fs/file-max
2870 Privileged processes (CAP_SYS_ADMIN) can override the file-max
2872 limit.
2873 /proc/sys/fs/file-nr
2875 This (read-only) file contains three numbers: the number of
2876 allocated file handles (i.e., the number of files presently
2877 opened); the number of free file handles; and the maximum number
2878 of file handles (i.e., the same value as /proc/sys/fs/file-max).
2879 If the number of allocated file handles is close to the maximum,
2880 you should consider increasing the maximum. Before Linux 2.6,
2881 the kernel allocated file handles dynamically, but it didn't
2882 free them again. Instead the free file handles were kept in a
2883 list for reallocation; the "free file handles" value indicates
2884 the size of that list. A large number of free file handles
2885 indicates that there was a past peak in the usage of open file
2886 handles. Since Linux 2.6, the kernel does deallocate freed file
2887 handles, and the "free file handles" value is always zero.
2888 /proc/sys/fs/inode-max (only present until Linux 2.2)
2890 This file contains the maximum number of in-memory inodes. This
2891 value should be 3–4 times larger than the value in file-max,
2892 since stdin, stdout and network sockets also need an inode to
2893 handle them. When you regularly run out of inodes, you need to
2894 increase this value.
2895 Starting with Linux 2.4, there is no longer a static limit on
2897 the number of inodes, and this file is removed.
2898 /proc/sys/fs/inode-nr
2900 This file contains the first two values from inode-state.
2901 /proc/sys/fs/inode-state
2903 This file contains seven numbers: nr_inodes, nr_free_inodes,
2904 preshrink, and four dummy values (always zero).
2905 nr_inodes is the number of inodes the system has allocated.
2907 nr_free_inodes represents the number of free inodes.
2908 preshrink is nonzero when the nr_inodes > inode-max and the sys‐
2910 tem needs to prune the inode list instead of allocating more;
2911 since Linux 2.4, this field is a dummy value (always zero).
2912 /proc/sys/fs/inotify (since Linux 2.6.13)
2914 This directory contains files max_queued_events,
2915 max_user_instances, and max_user_watches, that can be used to
2916 limit the amount of kernel memory consumed by the inotify inter‐
2917 face. For further details, see inotify(7).
2918 /proc/sys/fs/lease-break-time
2920 This file specifies the grace period that the kernel grants to a
2921 process holding a file lease (fcntl(2)) after it has sent a sig‐
2922 nal to that process notifying it that another process is waiting
2923 to open the file. If the lease holder does not remove or down‐
2924 grade the lease within this grace period, the kernel forcibly
2925 breaks the lease.
2926 /proc/sys/fs/leases-enable
2928 This file can be used to enable or disable file leases
2929 (fcntl(2)) on a system-wide basis. If this file contains the
2930 value 0, leases are disabled. A nonzero value enables leases.
2931 /proc/sys/fs/mount-max (since Linux 4.9)
2933 The value in this file specifies the maximum number of mounts
2934 that may exist in a mount namespace. The default value in this
2935 file is 100,000.
2936 /proc/sys/fs/mqueue (since Linux 2.6.6)
2938 This directory contains files msg_max, msgsize_max, and
2939 queues_max, controlling the resources used by POSIX message
2940 queues. See mq_overview(7) for details.
2941 /proc/sys/fs/nr_open (since Linux 2.6.25)
2943 This file imposes ceiling on the value to which the
2944 RLIMIT_NOFILE resource limit can be raised (see getrlimit(2)).
2945 This ceiling is enforced for both unprivileged and privileged
2946 process. The default value in this file is 1048576. (Before
2947 Linux 2.6.25, the ceiling for RLIMIT_NOFILE was hard-coded to
2948 the same value.)
2949 /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
2951 These files allow you to change the value of the fixed UID and
2952 GID. The default is 65534. Some filesystems support only
2953 16-bit UIDs and GIDs, although in Linux UIDs and GIDs are 32
2954 bits. When one of these filesystems is mounted with writes
2955 enabled, any UID or GID that would exceed 65535 is translated to
2956 the overflow value before being written to disk.
2957 /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
2959 See pipe(7).
2960 /proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)
2962 See pipe(7).
2963 /proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)
2965 See pipe(7).
2966 /proc/sys/fs/protected_hardlinks (since Linux 3.6)
2968 When the value in this file is 0, no restrictions are placed on
2969 the creation of hard links (i.e., this is the historical behav‐
2970 ior before Linux 3.6). When the value in this file is 1, a hard
2971 link can be created to a target file only if one of the follow‐
2972 ing conditions is true:
2973 * The calling process has the CAP_FOWNER capability in its user
2975 namespace and the file UID has a mapping in the namespace.
2976 * The filesystem UID of the process creating the link matches
2978 the owner (UID) of the target file (as described in creden‐
2979 tials(7), a process's filesystem UID is normally the same as
2980 its effective UID).
2981 * All of the following conditions are true:
2983 · the target is a regular file;
2985 · the target file does not have its set-user-ID mode bit
2987 enabled;
2988 · the target file does not have both its set-group-ID and
2990 group-executable mode bits enabled; and
2991 · the caller has permission to read and write the target
2993 file (either via the file's permissions mask or because
2994 it has suitable capabilities).
2995 The default value in this file is 0. Setting the value to 1
2997 prevents a longstanding class of security issues caused by hard-
2998 link-based time-of-check, time-of-use races, most commonly seen
2999 in world-writable directories such as /tmp. The common method
3000 of exploiting this flaw is to cross privilege boundaries when
3001 following a given hard link (i.e., a root process follows a hard
3002 link created by another user). Additionally, on systems without
3003 separated partitions, this stops unauthorized users from "pin‐
3004 ning" vulnerable set-user-ID and set-group-ID files against
3005 being upgraded by the administrator, or linking to special
3006 files.
3007 /proc/sys/fs/protected_symlinks (since Linux 3.6)
3009 When the value in this file is 0, no restrictions are placed on
3010 following symbolic links (i.e., this is the historical behavior
3011 before Linux 3.6). When the value in this file is 1, symbolic
3012 links are followed only in the following circumstances:
3013 * the filesystem UID of the process following the link matches
3015 the owner (UID) of the symbolic link (as described in creden‐
3016 tials(7), a process's filesystem UID is normally the same as
3017 its effective UID);
3018 * the link is not in a sticky world-writable directory; or
3020 * the symbolic link and its parent directory have the same
3022 owner (UID)
3023 A system call that fails to follow a symbolic link because of
3025 the above restrictions returns the error EACCES in errno.
3026 The default value in this file is 0. Setting the value to 1
3028 avoids a longstanding class of security issues based on time-of-
3029 check, time-of-use races when accessing symbolic links.
3030 /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
3032 The value in this file is assigned to a process's "dumpable"
3033 flag in the circumstances described in prctl(2). In effect, the
3034 value in this file determines whether core dump files are pro‐
3035 duced for set-user-ID or otherwise protected/tainted binaries.
3036 The "dumpable" setting also affects the ownership of files in a
3037 process's /proc/[pid] directory, as described above.
3038 Three different integer values can be specified:
3040 0 (default)
3042 This provides the traditional (pre-Linux 2.6.13) behav‐
3043 ior. A core dump will not be produced for a process
3044 which has changed credentials (by calling seteuid(2),
3045 setgid(2), or similar, or by executing a set-user-ID or
3046 set-group-ID program) or whose binary does not have read
3047 permission enabled.
3048 1 ("debug")
3050 All processes dump core when possible. (Reasons why a
3051 process might nevertheless not dump core are described in
3052 core(5).) The core dump is owned by the filesystem user
3053 ID of the dumping process and no security is applied.
3054 This is intended for system debugging situations only:
3055 this mode is insecure because it allows unprivileged
3056 users to examine the memory contents of privileged pro‐
3057 cesses.
3058 2 ("suidsafe")
3060 Any binary which normally would not be dumped (see "0"
3061 above) is dumped readable by root only. This allows the
3062 user to remove the core dump file but not to read it.
3063 For security reasons core dumps in this mode will not
3064 overwrite one another or other files. This mode is
3065 appropriate when administrators are attempting to debug
3066 problems in a normal environment.
3067 Additionally, since Linux 3.6, /proc/sys/kernel/core_pat‐
3069 tern must either be an absolute pathname or a pipe com‐
3070 mand, as detailed in core(5). Warnings will be written
3071 to the kernel log if core_pattern does not follow these
3072 rules, and no core dump will be produced.
3073 For details of the effect of a process's "dumpable" setting on
3075 ptrace access mode checking, see ptrace(2).
3076 /proc/sys/fs/super-max
3078 This file controls the maximum number of superblocks, and thus
3079 the maximum number of mounted filesystems the kernel can have.
3080 You need increase only super-max if you need to mount more
3081 filesystems than the current value in super-max allows you to.
3082 /proc/sys/fs/super-nr
3084 This file contains the number of filesystems currently mounted.
3085 /proc/sys/kernel
3087 This directory contains files controlling a range of kernel
3088 parameters, as described below.
3089 /proc/sys/kernel/acct
3091 This file contains three numbers: highwater, lowwater, and fre‐
3092 quency. If BSD-style process accounting is enabled, these val‐
3093 ues control its behavior. If free space on filesystem where the
3094 log lives goes below lowwater percent, accounting suspends. If
3095 free space gets above highwater percent, accounting resumes.
3096 frequency determines how often the kernel checks the amount of
3097 free space (value is in seconds). Default values are 4, 2 and
3098 30. That is, suspend accounting if 2% or less space is free;
3099 resume it if 4% or more space is free; consider information
3100 about amount of free space valid for 30 seconds.
3101 /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
3103 From Linux 2.6.27 to 3.18, this file was used to control recom‐
3104 puting of the value in /proc/sys/kernel/msgmni upon the addition
3105 or removal of memory or upon IPC namespace creation/removal.
3106 Echoing "1" into this file enabled msgmni automatic recomputing
3107 (and triggered a recomputation of msgmni based on the current
3108 amount of available memory and number of IPC namespaces). Echo‐
3109 ing "0" disabled automatic recomputing. (Automatic recomputing
3110 was also disabled if a value was explicitly assigned to
3111 /proc/sys/kernel/msgmni.) The default value in auto_msgmni was
3112 1.
3113 Since Linux 3.19, the content of this file has no effect
3115 (because msgmni defaults to near the maximum value possible),
3116 and reads from this file always return the value "0".
3117 /proc/sys/kernel/cap_last_cap (since Linux 3.2)
3119 See capabilities(7).
3120 /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
3122 This file holds the value of the kernel capability bounding set
3123 (expressed as a signed decimal number). This set is ANDed
3124 against the capabilities permitted to a process during
3125 execve(2). Starting with Linux 2.6.25, the system-wide capabil‐
3126 ity bounding set disappeared, and was replaced by a per-thread
3127 bounding set; see capabilities(7).
3128 /proc/sys/kernel/core_pattern
3130 See core(5).
3131 /proc/sys/kernel/core_pipe_limit
3133 See core(5).
3134 /proc/sys/kernel/core_uses_pid
3136 See core(5).
3137 /proc/sys/kernel/ctrl-alt-del
3139 This file controls the handling of Ctrl-Alt-Del from the key‐
3140 board. When the value in this file is 0, Ctrl-Alt-Del is
3141 trapped and sent to the init(1) program to handle a graceful
3142 restart. When the value is greater than zero, Linux's reaction
3143 to a Vulcan Nerve Pinch (tm) will be an immediate reboot, with‐
3144 out even syncing its dirty buffers. Note: when a program (like
3145 dosemu) has the keyboard in "raw" mode, the ctrl-alt-del is
3146 intercepted by the program before it ever reaches the kernel tty
3147 layer, and it's up to the program to decide what to do with it.
3148 /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
3150 The value in this file determines who can see kernel syslog con‐
3151 tents. A value of 0 in this file imposes no restrictions. If
3152 the value is 1, only privileged users can read the kernel sys‐
3153 log. (See syslog(2) for more details.) Since Linux 3.4, only
3154 users with the CAP_SYS_ADMIN capability may change the value in
3155 this file.
3156 /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
3158 can be used to set the NIS/YP domainname and the hostname of
3159 your box in exactly the same way as the commands domainname(1)
3160 and hostname(1), that is:
3161 # echo 'darkstar' > /proc/sys/kernel/hostname
3163 # echo 'mydomain' > /proc/sys/kernel/domainname
3164 has the same effect as
3166 # hostname 'darkstar'
3168 # domainname 'mydomain'
3169 Note, however, that the classic darkstar.frop.org has the host‐
3171 name "darkstar" and DNS (Internet Domain Name Server) domainname
3172 "frop.org", not to be confused with the NIS (Network Information
3173 Service) or YP (Yellow Pages) domainname. These two domain
3174 names are in general different. For a detailed discussion see
3175 the hostname(1) man page.
3176 /proc/sys/kernel/hotplug
3178 This file contains the path for the hotplug policy agent. The
3179 default value in this file is /sbin/hotplug.
3180 /proc/sys/kernel/htab-reclaim (before Linux 2.4.9.2)
3182 (PowerPC only) If this file is set to a nonzero value, the Pow‐
3183 erPC htab (see kernel file Documentation/powerpc/ppc_htab.txt)
3184 is pruned each time the system hits the idle loop.
3185 /proc/sys/kernel/keys/*
3187 This directory contains various files that define parameters and
3188 limits for the key-management facility. These files are
3189 described in keyrings(7).
3190 /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
3192 The value in this file determines whether kernel addresses are
3193 exposed via /proc files and other interfaces. A value of 0 in
3194 this file imposes no restrictions. If the value is 1, kernel
3195 pointers printed using the %pK format specifier will be replaced
3196 with zeros unless the user has the CAP_SYSLOG capability. If
3197 the value is 2, kernel pointers printed using the %pK format
3198 specifier will be replaced with zeros regardless of the user's
3199 capabilities. The initial default value for this file was 1,
3200 but the default was changed to 0 in Linux 2.6.39. Since Linux
3201 3.4, only users with the CAP_SYS_ADMIN capability can change the
3202 value in this file.
3203 /proc/sys/kernel/l2cr
3205 (PowerPC only) This file contains a flag that controls the L2
3206 cache of G3 processor boards. If 0, the cache is disabled.
3207 Enabled if nonzero.
3208 /proc/sys/kernel/modprobe
3210 This file contains the path for the kernel module loader. The
3211 default value is /sbin/modprobe. The file is present only if
3212 the kernel is built with the CONFIG_MODULES (CONFIG_KMOD in
3213 Linux 2.6.26 and earlier) option enabled. It is described by
3214 the Linux kernel source file Documentation/kmod.txt (present
3215 only in kernel 2.4 and earlier).
3216 /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
3218 A toggle value indicating if modules are allowed to be loaded in
3219 an otherwise modular kernel. This toggle defaults to off (0),
3220 but can be set true (1). Once true, modules can be neither
3221 loaded nor unloaded, and the toggle cannot be set back to false.
3222 The file is present only if the kernel is built with the CON‐
3223 FIG_MODULES option enabled.
3224 /proc/sys/kernel/msgmax (since Linux 2.2)
3226 This file defines a system-wide limit specifying the maximum
3227 number of bytes in a single message written on a System V mes‐
3228 sage queue.
3229 /proc/sys/kernel/msgmni (since Linux 2.4)
3231 This file defines the system-wide limit on the number of message
3232 queue identifiers. See also /proc/sys/kernel/auto_msgmni.
3233 /proc/sys/kernel/msgmnb (since Linux 2.2)
3235 This file defines a system-wide parameter used to initialize the
3236 msg_qbytes setting for subsequently created message queues. The
3237 msg_qbytes setting specifies the maximum number of bytes that
3238 may be written to the message queue.
3239 /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
3241 This is a read-only file that displays the upper limit on the
3242 number of a process's group memberships.
3243 /proc/sys/kernel/ns_last_pid (since Linux 3.3)
3245 See pid_namespaces(7).
3246 /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
3248 These files give substrings of /proc/version.
3249 /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
3251 These files duplicate the files /proc/sys/fs/overflowgid and
3252 /proc/sys/fs/overflowuid.
3253 /proc/sys/kernel/panic
3255 This file gives read/write access to the kernel variable
3256 panic_timeout. If this is zero, the kernel will loop on a
3257 panic; if nonzero, it indicates that the kernel should autore‐
3258 boot after this number of seconds. When you use the software
3259 watchdog device driver, the recommended setting is 60.
3260 /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
3262 This file controls the kernel's behavior when an oops or BUG is
3263 encountered. If this file contains 0, then the system tries to
3264 continue operation. If it contains 1, then the system delays a
3265 few seconds (to give klogd time to record the oops output) and
3266 then panics. If the /proc/sys/kernel/panic file is also
3267 nonzero, then the machine will be rebooted.
3268 /proc/sys/kernel/pid_max (since Linux 2.5.34)
3270 This file specifies the value at which PIDs wrap around (i.e.,
3271 the value in this file is one greater than the maximum PID).
3272 PIDs greater than this value are not allocated; thus, the value
3273 in this file also acts as a system-wide limit on the total num‐
3274 ber of processes and threads. The default value for this file,
3275 32768, results in the same range of PIDs as on earlier kernels.
3276 On 32-bit platforms, 32768 is the maximum value for pid_max. On
3277 64-bit systems, pid_max can be set to any value up to 2^22
3278 (PID_MAX_LIMIT, approximately 4 million).
3279 /proc/sys/kernel/powersave-nap (PowerPC only)
3281 This file contains a flag. If set, Linux-PPC will use the "nap"
3282 mode of powersaving, otherwise the "doze" mode will be used.
3283 /proc/sys/kernel/printk
3285 See syslog(2).
3286 /proc/sys/kernel/pty (since Linux 2.6.4)
3288 This directory contains two files relating to the number of UNIX
3289 98 pseudoterminals (see pts(4)) on the system.
3290 /proc/sys/kernel/pty/max
3292 This file defines the maximum number of pseudoterminals.
3293 /proc/sys/kernel/pty/nr
3295 This read-only file indicates how many pseudoterminals are cur‐
3296 rently in use.
3297 /proc/sys/kernel/random
3299 This directory contains various parameters controlling the oper‐
3300 ation of the file /dev/random. See random(4) for further infor‐
3301 mation.
3302 /proc/sys/kernel/random/uuid (since Linux 2.4)
3304 Each read from this read-only file returns a randomly generated
3305 128-bit UUID, as a string in the standard UUID format.
3306 /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
3308 Select the address space layout randomization (ASLR) policy for
3309 the system (on architectures that support ASLR). Three values
3310 are supported for this file:
3311 0 Turn ASLR off. This is the default for architectures that
3313 don't support ASLR, and when the kernel is booted with the
3314 norandmaps parameter.
3315 1 Make the addresses of mmap(2) allocations, the stack, and the
3317 VDSO page randomized. Among other things, this means that
3318 shared libraries will be loaded at randomized addresses. The
3319 text segment of PIE-linked binaries will also be loaded at a
3320 randomized address. This value is the default if the kernel
3321 was configured with CONFIG_COMPAT_BRK.
3322 2 (Since Linux 2.6.25) Also support heap randomization. This
3324 value is the default if the kernel was not configured with
3325 CONFIG_COMPAT_BRK.
3326 /proc/sys/kernel/real-root-dev
3328 This file is documented in the Linux kernel source file Documen‐
3329 tation/admin-guide/initrd.rst (or Documentation/initrd.txt
3330 before Linux 4.10).
3331 /proc/sys/kernel/reboot-cmd (Sparc only)
3333 This file seems to be a way to give an argument to the SPARC
3334 ROM/Flash boot loader. Maybe to tell it what to do after
3335 rebooting?
3336 /proc/sys/kernel/rtsig-max
3338 (Only in kernels up to and including 2.6.7; see setrlimit(2))
3339 This file can be used to tune the maximum number of POSIX real-
3340 time (queued) signals that can be outstanding in the system.
3341 /proc/sys/kernel/rtsig-nr
3343 (Only in kernels up to and including 2.6.7.) This file shows
3344 the number of POSIX real-time signals currently queued.
3345 /proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)
3347 See sched(7).
3348 /proc/sys/kernel/sched_child_runs_first (since Linux 2.6.23)
3350 If this file contains the value zero, then, after a fork(2), the
3351 parent is first scheduled on the CPU. If the file contains a
3352 nonzero value, then the child is scheduled first on the CPU.
3353 (Of course, on a multiprocessor system, the parent and the child
3354 might both immediately be scheduled on a CPU.)
3355 /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
3357 See sched_rr_get_interval(2).
3358 /proc/sys/kernel/sched_rt_period_us (since Linux 2.6.25)
3360 See sched(7).
3361 /proc/sys/kernel/sched_rt_runtime_us (since Linux 2.6.25)
3363 See sched(7).
3364 /proc/sys/kernel/seccomp (since Linux 4.14)
3366 This directory provides additional seccomp information and con‐
3367 figuration. See seccomp(2) for further details.
3368 /proc/sys/kernel/sem (since Linux 2.4)
3370 This file contains 4 numbers defining limits for System V IPC
3371 semaphores. These fields are, in order:
3372 SEMMSL The maximum semaphores per semaphore set.
3374 SEMMNS A system-wide limit on the number of semaphores in all
3376 semaphore sets.
3377 SEMOPM The maximum number of operations that may be specified
3379 in a semop(2) call.
3380 SEMMNI A system-wide limit on the maximum number of semaphore
3382 identifiers.
3383 /proc/sys/kernel/sg-big-buff
3385 This file shows the size of the generic SCSI device (sg) buffer.
3386 You can't tune it just yet, but you could change it at compile
3387 time by editing include/scsi/sg.h and changing the value of
3388 SG_BIG_BUFF. However, there shouldn't be any reason to change
3389 this value.
3390 /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
3392 If this file is set to 1, all System V shared memory segments
3393 will be marked for destruction as soon as the number of attached
3394 processes falls to zero; in other words, it is no longer possi‐
3395 ble to create shared memory segments that exist independently of
3396 any attached process.
3397 The effect is as though a shmctl(2) IPC_RMID is performed on all
3399 existing segments as well as all segments created in the future
3400 (until this file is reset to 0). Note that existing segments
3401 that are attached to no process will be immediately destroyed
3402 when this file is set to 1. Setting this option will also
3403 destroy segments that were created, but never attached, upon
3404 termination of the process that created the segment with
3405 shmget(2).
3406 Setting this file to 1 provides a way of ensuring that all Sys‐
3408 tem V shared memory segments are counted against the resource
3409 usage and resource limits (see the description of RLIMIT_AS in
3410 getrlimit(2)) of at least one process.
3411 Because setting this file to 1 produces behavior that is non‐
3413 standard and could also break existing applications, the default
3414 value in this file is 0. Set this file to 1 only if you have a
3415 good understanding of the semantics of the applications using
3416 System V shared memory on your system.
3417 /proc/sys/kernel/shmall (since Linux 2.2)
3419 This file contains the system-wide limit on the total number of
3420 pages of System V shared memory.
3421 /proc/sys/kernel/shmmax (since Linux 2.2)
3423 This file can be used to query and set the run-time limit on the
3424 maximum (System V IPC) shared memory segment size that can be
3425 created. Shared memory segments up to 1GB are now supported in
3426 the kernel. This value defaults to SHMMAX.
3427 /proc/sys/kernel/shmmni (since Linux 2.4)
3429 This file specifies the system-wide maximum number of System V
3430 shared memory segments that can be created.
3431 /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
3433 The value in this file determines how the file offset affects
3434 the behavior of updating entries in files under /proc/sys. The
3435 file has three possible values:
3436 -1 This provides legacy handling, with no printk warnings.
3438 Each write(2) must fully contain the value to be written,
3439 and multiple writes on the same file descriptor will over‐
3440 write the entire value, regardless of the file position.
3441 0 (default) This provides the same behavior as for -1, but
3443 printk warnings are written for processes that perform
3444 writes when the file offset is not 0.
3445 1 Respect the file offset when writing strings into /proc/sys
3447 files. Multiple writes will append to the value buffer.
3448 Anything written beyond the maximum length of the value buf‐
3449 fer will be ignored. Writes to numeric /proc/sys entries
3450 must always be at file offset 0 and the value must be fully
3451 contained in the buffer provided to write(2).
3452 /proc/sys/kernel/sysrq
3454 This file controls the functions allowed to be invoked by the
3455 SysRq key. By default, the file contains 1 meaning that every
3456 possible SysRq request is allowed (in older kernel versions,
3457 SysRq was disabled by default, and you were required to specifi‐
3458 cally enable it at run-time, but this is not the case any more).
3459 Possible values in this file are:
3460 0 Disable sysrq completely
3462 1 Enable all functions of sysrq
3464 > 1 Bit mask of allowed sysrq functions, as follows:
3466 2 Enable control of console logging level
3467 4 Enable control of keyboard (SAK, unraw)
3468 8 Enable debugging dumps of processes etc.
3469 16 Enable sync command
3470 32 Enable remount read-only
3471 64 Enable signaling of processes (term, kill, oom-kill)
3472 128 Allow reboot/poweroff
3473 256 Allow nicing of all real-time tasks
3474 This file is present only if the CONFIG_MAGIC_SYSRQ kernel con‐
3476 figuration option is enabled. For further details see the Linux
3477 kernel source file Documentation/admin-guide/sysrq.rst (or Docu‐
3478 mentation/sysrq.txt before Linux 4.10).
3479 /proc/sys/kernel/version
3481 This file contains a string such as:
3482 #5 Wed Feb 25 21:49:24 MET 1998
3484 The "#5" means that this is the fifth kernel built from this
3486 source base and the date following it indicates the time the
3487 kernel was built.
3488 /proc/sys/kernel/threads-max (since Linux 2.3.11)
3490 This file specifies the system-wide limit on the number of
3491 threads (tasks) that can be created on the system.
3492 Since Linux 4.1, the value that can be written to threads-max is
3494 bounded. The minimum value that can be written is 20. The max‐
3495 imum value that can be written is given by the constant
3496 FUTEX_TID_MASK [22m(0x3fffffff). If a value outside of this range
3497 is written to threads-max, the error EINVAL occurs.
3498 The value written is checked against the available RAM pages.
3500 If the thread structures would occupy too much (more than 1/8th)
3501 of the available RAM pages, threads-max is reduced accordingly.
3502 /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
3504 See ptrace(2).
3505 /proc/sys/kernel/zero-paged (PowerPC only)
3507 This file contains a flag. When enabled (nonzero), Linux-PPC
3508 will pre-zero pages in the idle loop, possibly speeding up
3509 get_free_pages.
3510 /proc/sys/net
3512 This directory contains networking stuff. Explanations for some
3513 of the files under this directory can be found in tcp(7) and
3514 ip(7).
3515 /proc/sys/net/core/bpf_jit_enable
3517 See bpf(2).
3518 /proc/sys/net/core/somaxconn
3520 This file defines a ceiling value for the backlog argument of
3521 listen(2); see the listen(2) manual page for details.
3522 /proc/sys/proc
3524 This directory may be empty.
3525 /proc/sys/sunrpc
3527 This directory supports Sun remote procedure call for network
3528 filesystem (NFS). On some systems, it is not present.
3529 /proc/sys/user (since Linux 4.9)
3531 See namespaces(7).
3532 /proc/sys/vm
3534 This directory contains files for memory management tuning, buf‐
3535 fer and cache management.
3536 /proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)
3538 This file defines the amount of free memory (in KiB) on the sys‐
3539 tem that should be reserved for users with the capability
3540 CAP_SYS_ADMIN.
3541 The default value in this file is the minimum of [3% of free
3543 pages, 8MiB] expressed as KiB. The default is intended to pro‐
3544 vide enough for the superuser to log in and kill a process, if
3545 necessary, under the default overcommit 'guess' mode (i.e., 0 in
3546 /proc/sys/vm/overcommit_memory).
3547 Systems running in "overcommit never" mode (i.e., 2 in
3549 /proc/sys/vm/overcommit_memory) should increase the value in
3550 this file to account for the full virtual memory size of the
3551 programs used to recover (e.g., login(1) ssh(1), and top(1))
3552 Otherwise, the superuser may not be able to log in to recover
3553 the system. For example, on x86-64 a suitable value is 131072
3554 (128MiB reserved).
3555 Changing the value in this file takes effect whenever an appli‐
3557 cation requests memory.
3558 /proc/sys/vm/compact_memory (since Linux 2.6.35)
3560 When 1 is written to this file, all zones are compacted such
3561 that free memory is available in contiguous blocks where possi‐
3562 ble. The effect of this action can be seen by examining
3563 /proc/buddyinfo.
3564 Present only if the kernel was configured with CONFIG_COM‐
3566 PACTION.
3567 /proc/sys/vm/drop_caches (since Linux 2.6.16)
3569 Writing to this file causes the kernel to drop clean caches,
3570 dentries, and inodes from memory, causing that memory to become
3571 free. This can be useful for memory management testing and per‐
3572 forming reproducible filesystem benchmarks. Because writing to
3573 this file causes the benefits of caching to be lost, it can
3574 degrade overall system performance.
3575 To free pagecache, use:
3577 echo 1 > /proc/sys/vm/drop_caches
3579 To free dentries and inodes, use:
3581 echo 2 > /proc/sys/vm/drop_caches
3583 To free pagecache, dentries and inodes, use:
3585 echo 3 > /proc/sys/vm/drop_caches
3587 Because writing to this file is a nondestructive operation and
3589 dirty objects are not freeable, the user should run sync(1)
3590 first.
3591 /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
3593 If nonzero, this disables the new 32-bit memory-mapping layout;
3594 the kernel will use the legacy (2.4) layout for all processes.
3595 /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
3597 Control how to kill processes when an uncorrected memory error
3598 (typically a 2-bit error in a memory module) that cannot be han‐
3599 dled by the kernel is detected in the background by hardware.
3600 In some cases (like the page still having a valid copy on disk),
3601 the kernel will handle the failure transparently without affect‐
3602 ing any applications. But if there is no other up-to-date copy
3603 of the data, it will kill processes to prevent any data corrup‐
3604 tions from propagating.
3605 The file has one of the following values:
3607 1: Kill all processes that have the corrupted-and-not-reload‐
3609 able page mapped as soon as the corruption is detected.
3610 Note that this is not supported for a few types of pages,
3611 such as kernel internally allocated data or the swap cache,
3612 but works for the majority of user pages.
3613 0: Unmap the corrupted page from all processes and kill a
3615 process only if it tries to access the page.
3616 The kill is performed using a SIGBUS signal with si_code set to
3618 BUS_MCEERR_AO. Processes can handle this if they want to; see
3619 sigaction(2) for more details.
3620 This feature is active only on architectures/platforms with
3622 advanced machine check handling and depends on the hardware
3623 capabilities.
3624 Applications can override the memory_failure_early_kill setting
3626 individually with the prctl(2) PR_MCE_KILL operation.
3627 Present only if the kernel was configured with CONFIG_MEM‐
3629 ORY_FAILURE.
3630 /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
3632 Enable memory failure recovery (when supported by the platform)
3633 1: Attempt recovery.
3635 0: Always panic on a memory failure.
3637 Present only if the kernel was configured with CONFIG_MEM‐
3639 ORY_FAILURE.
3640 /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
3642 Enables a system-wide task dump (excluding kernel threads) to be
3643 produced when the kernel performs an OOM-killing. The dump
3644 includes the following information for each task (thread,
3645 process): thread ID, real user ID, thread group ID (process ID),
3646 virtual memory size, resident set size, the CPU that the task is
3647 scheduled on, oom_adj score (see the description of
3648 /proc/[pid]/oom_adj), and command name. This is helpful to
3649 determine why the OOM-killer was invoked and to identify the
3650 rogue task that caused it.
3651 If this contains the value zero, this information is suppressed.
3653 On very large systems with thousands of tasks, it may not be
3654 feasible to dump the memory state information for each one.
3655 Such systems should not be forced to incur a performance penalty
3656 in OOM situations when the information may not be desired.
3657 If this is set to nonzero, this information is shown whenever
3659 the OOM-killer actually kills a memory-hogging task.
3660 The default value is 0.
3662 /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
3664 This enables or disables killing the OOM-triggering task in out-
3665 of-memory situations.
3666 If this is set to zero, the OOM-killer will scan through the
3668 entire tasklist and select a task based on heuristics to kill.
3669 This normally selects a rogue memory-hogging task that frees up
3670 a large amount of memory when killed.
3671 If this is set to nonzero, the OOM-killer simply kills the task
3673 that triggered the out-of-memory condition. This avoids a pos‐
3674 sibly expensive tasklist scan.
3675 If /proc/sys/vm/panic_on_oom is nonzero, it takes precedence
3677 over whatever value is used in /proc/sys/vm/oom_kill_allocat‐
3678 ing_task.
3679 The default value is 0.
3681 /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
3683 This writable file provides an alternative to /proc/sys/vm/over‐
3684 commit_ratio for controlling the CommitLimit when
3685 /proc/sys/vm/overcommit_memory has the value 2. It allows the
3686 amount of memory overcommitting to be specified as an absolute
3687 value (in kB), rather than as a percentage, as is done with
3688 overcommit_ratio. This allows for finer-grained control of Com‐
3689 mitLimit on systems with extremely large memory sizes.
3690 Only one of overcommit_kbytes or overcommit_ratio can have an
3692 effect: if overcommit_kbytes has a nonzero value, then it is
3693 used to calculate CommitLimit, otherwise overcommit_ratio is
3694 used. Writing a value to either of these files causes the value
3695 in the other file to be set to zero.
3696 /proc/sys/vm/overcommit_memory
3698 This file contains the kernel virtual memory accounting mode.
3699 Values are:
3700 0: heuristic overcommit (this is the default)
3702 1: always overcommit, never check
3703 2: always check, never overcommit
3704 In mode 0, calls of mmap(2) with MAP_NORESERVE are not checked,
3706 and the default check is very weak, leading to the risk of get‐
3707 ting a process "OOM-killed".
3708 In mode 1, the kernel pretends there is always enough memory,
3710 until memory actually runs out. One use case for this mode is
3711 scientific computing applications that employ large sparse
3712 arrays. In Linux kernel versions before 2.6.0, any nonzero
3713 value implies mode 1.
3714 In mode 2 (available since Linux 2.6), the total virtual address
3716 space that can be allocated (CommitLimit in /proc/meminfo) is
3717 calculated as
3718 CommitLimit = (total_RAM - total_huge_TLB) *
3720 overcommit_ratio / 100 + total_swap
3721 where:
3723 * total_RAM is the total amount of RAM on the system;
3725 * total_huge_TLB is the amount of memory set aside for
3727 huge pages;
3728 * overcommit_ratio is the value in /proc/sys/vm/overcom‐
3730 mit_ratio; and
3731 * total_swap is the amount of swap space.
3733 For example, on a system with 16GB of physical RAM, 16GB of
3735 swap, no space dedicated to huge pages, and an overcommit_ratio
3736 of 50, this formula yields a CommitLimit of 24GB.
3737 Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes
3739 is nonzero, then CommitLimit is instead calculated as:
3740 CommitLimit = overcommit_kbytes + total_swap
3742 See also the description of /proc/sys/vm/admiin_reserve_kbytes
3744 and /proc/sys/vm/user_reserve_kbytes.
3745 /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
3747 This writable file defines a percentage by which memory can be
3748 overcommitted. The default value in the file is 50. See the
3749 description of /proc/sys/vm/overcommit_memory.
3750 /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
3752 This enables or disables a kernel panic in an out-of-memory sit‐
3753 uation.
3754 If this file is set to the value 0, the kernel's OOM-killer will
3756 kill some rogue process. Usually, the OOM-killer is able to
3757 kill a rogue process and the system will survive.
3758 If this file is set to the value 1, then the kernel normally
3760 panics when out-of-memory happens. However, if a process limits
3761 allocations to certain nodes using memory policies (mbind(2)
3762 MPOL_BIND) or cpusets (cpuset(7)) and those nodes reach memory
3763 exhaustion status, one process may be killed by the OOM-killer.
3764 No panic occurs in this case: because other nodes' memory may be
3765 free, this means the system as a whole may not have reached an
3766 out-of-memory situation yet.
3767 If this file is set to the value 2, the kernel always panics
3769 when an out-of-memory condition occurs.
3770 The default value is 0. 1 and 2 are for failover of clustering.
3772 Select either according to your policy of failover.
3773 /proc/sys/vm/swappiness
3775 The value in this file controls how aggressively the kernel will
3776 swap memory pages. Higher values increase aggressiveness, lower
3777 values decrease aggressiveness. The default value is 60.
3778 /proc/sys/vm/user_reserve_kbytes (since Linux 3.10)
3780 Specifies an amount of memory (in KiB) to reserve for user pro‐
3781 cesses, This is intended to prevent a user from starting a sin‐
3782 gle memory hogging process, such that they cannot recover (kill
3783 the hog). The value in this file has an effect only when
3784 /proc/sys/vm/overcommit_memory is set to 2 ("overcommit never"
3785 mode). In this case, the system reserves an amount of memory
3786 that is the minimum of [3% of current process size,
3787 user_reserve_kbytes].
3788 The default value in this file is the minimum of [3% of free
3790 pages, 128MiB] expressed as KiB.
3791 If the value in this file is set to zero, then a user will be
3793 allowed to allocate all free memory with a single process (minus
3794 the amount reserved by /proc/sys/vm/admin_reserve_kbytes). Any
3795 subsequent attempts to execute a command will result in "fork:
3796 Cannot allocate memory".
3797 Changing the value in this file takes effect whenever an appli‐
3799 cation requests memory.
3800 /proc/sysrq-trigger (since Linux 2.4.21)
3802 Writing a character to this file triggers the same SysRq func‐
3803 tion as typing ALT-SysRq-<character> (see the description of
3804 /proc/sys/kernel/sysrq). This file is normally writable only by
3805 root. For further details see the Linux kernel source file Doc‐
3806 umentation/admin-guide/sysrq.rst (or Documentation/sysrq.txt
3807 before Linux 4.10).
3808 /proc/sysvipc
3810 Subdirectory containing the pseudo-files msg, sem and shm.
3811 These files list the System V Interprocess Communication (IPC)
3812 objects (respectively: message queues, semaphores, and shared
3813 memory) that currently exist on the system, providing similar
3814 information to that available via ipcs(1). These files have
3815 headers and are formatted (one IPC object per line) for easy
3816 understanding. svipc(7) provides further background on the
3817 information shown by these files.
3818 /proc/thread-self (since Linux 3.17)
3820 This directory refers to the thread accessing the /proc filesys‐
3821 tem, and is identical to the /proc/self/task/[tid] directory
3822 named by the process thread ID ([tid]) of the same thread.
3823 /proc/timer_list (since Linux 2.6.21)
3825 This read-only file exposes a list of all currently pending
3826 (high-resolution) timers, all clock-event sources, and their
3827 parameters in a human-readable form.
3828 /proc/timer_stats (from Linux 2.6.21 until Linux 4.10)
3830 This is a debugging facility to make timer (ab)use in a Linux
3831 system visible to kernel and user-space developers. It can be
3832 used by kernel and user-space developers to verify that their
3833 code does not make undue use of timers. The goal is to avoid
3834 unnecessary wakeups, thereby optimizing power consumption.
3835 If enabled in the kernel (CONFIG_TIMER_STATS), but not used, it
3837 has almost zero runtime overhead and a relatively small data-
3838 structure overhead. Even if collection is enabled at runtime,
3839 overhead is low: all the locking is per-CPU and lookup is
3840 hashed.
3841 The /proc/timer_stats file is used both to control sampling
3843 facility and to read out the sampled information.
3844 The timer_stats functionality is inactive on bootup. A sampling
3846 period can be started using the following command:
3847 # echo 1 > /proc/timer_stats
3849 The following command stops a sampling period:
3851 # echo 0 > /proc/timer_stats
3853 The statistics can be retrieved by:
3855 $ cat /proc/timer_stats
3857 While sampling is enabled, each readout from /proc/timer_stats
3859 will see newly updated statistics. Once sampling is disabled,
3860 the sampled information is kept until a new sample period is
3861 started. This allows multiple readouts.
3862 Sample output from /proc/timer_stats:
3864 $ cat /proc/timer_stats
3866 Timer Stats Version: v0.3
3867 Sample period: 1.764 s
3868 Collection: active
3869 255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer)
3870 71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer)
3871 58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer)
3872 4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn)
3873 17, 7 rcu_sched rcu_gp_kthread (process_timeout)
3874 ...
3875 1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn)
3876 1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn)
3877 1029 total events, 583.333 events/sec
3878 The output columns are:
3880 * a count of the number of events, optionally (since Linux
3882 2.6.23) followed by the letter 'D' if this is a deferrable
3883 timer;
3884 * the PID of the process that initialized the timer;
3886 * the name of the process that initialized the timer;
3888 * the function where the timer was initialized; and
3890 * (in parentheses) the callback function that is associated
3892 with the timer.
3893 During the Linux 4.11 development cycle, this file was removed
3895 because of security concerns, as it exposes information across
3896 namespaces. Furthermore, it is possible to obtain the same
3897 information via in-kernel tracing facilities such as ftrace.
3898 /proc/tty
3900 Subdirectory containing the pseudo-files and subdirectories for
3901 tty drivers and line disciplines.
3902 /proc/uptime
3904 This file contains two numbers: the uptime of the system (sec‐
3905 onds), and the amount of time spent in idle process (seconds).
3906 /proc/version
3908 This string identifies the kernel version that is currently run‐
3909 ning. It includes the contents of /proc/sys/kernel/ostype,
3910 /proc/sys/kernel/osrelease and /proc/sys/kernel/version. For
3911 example:
3912 Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994
3914 /proc/vmstat (since Linux 2.6.0)
3916 This file displays various virtual memory statistics. Each line
3917 of this file contains a single name-value pair, delimited by
3918 white space. Some lines are present only if the kernel was con‐
3919 figured with suitable options. (In some cases, the options
3920 required for particular files have changed across kernel ver‐
3921 sions, so they are not listed here. Details can be found by
3922 consulting the kernel source code.) The following fields may be
3923 present:
3924 nr_free_pages (since Linux 2.6.31)
3926 nr_alloc_batch (since Linux 3.12)
3928 nr_inactive_anon (since Linux 2.6.28)
3930 nr_active_anon (since Linux 2.6.28)
3932 nr_inactive_file (since Linux 2.6.28)
3934 nr_active_file (since Linux 2.6.28)
3936 nr_unevictable (since Linux 2.6.28)
3938 nr_mlock (since Linux 2.6.28)
3940 nr_anon_pages (since Linux 2.6.18)
3942 nr_mapped (since Linux 2.6.0)
3944 nr_file_pages (since Linux 2.6.18)
3946 nr_dirty (since Linux 2.6.0)
3948 nr_writeback (since Linux 2.6.0)
3950 nr_slab_reclaimable (since Linux 2.6.19)
3952 nr_slab_unreclaimable (since Linux 2.6.19)
3954 nr_page_table_pages (since Linux 2.6.0)
3956 nr_kernel_stack (since Linux 2.6.32)
3958 Amount of memory allocated to kernel stacks.
3959 nr_unstable (since Linux 2.6.0)
3961 nr_bounce (since Linux 2.6.12)
3963 nr_vmscan_write (since Linux 2.6.19)
3965 nr_vmscan_immediate_reclaim (since Linux 3.2)
3967 nr_writeback_temp (since Linux 2.6.26)
3969 nr_isolated_anon (since Linux 2.6.32)
3971 nr_isolated_file (since Linux 2.6.32)
3973 nr_shmem (since Linux 2.6.32)
3975 Pages used by shmem and tmpfs(5).
3976 nr_dirtied (since Linux 2.6.37)
3978 nr_written (since Linux 2.6.37)
3980 nr_pages_scanned (since Linux 3.17)
3982 numa_hit (since Linux 2.6.18)
3984 numa_miss (since Linux 2.6.18)
3986 numa_foreign (since Linux 2.6.18)
3988 numa_interleave (since Linux 2.6.18)
3990 numa_local (since Linux 2.6.18)
3992 numa_other (since Linux 2.6.18)
3994 workingset_refault (since Linux 3.15)
3996 workingset_activate (since Linux 3.15)
3998 workingset_nodereclaim (since Linux 3.15)
4000 nr_anon_transparent_hugepages (since Linux 2.6.38)
4002 nr_free_cma (since Linux 3.7)
4004 Number of free CMA (Contiguous Memory Allocator) pages.
4005 nr_dirty_threshold (since Linux 2.6.37)
4007 nr_dirty_background_threshold (since Linux 2.6.37)
4009 pgpgin (since Linux 2.6.0)
4011 pgpgout (since Linux 2.6.0)
4013 pswpin (since Linux 2.6.0)
4015 pswpout (since Linux 2.6.0)
4017 pgalloc_dma (since Linux 2.6.5)
4019 pgalloc_dma32 (since Linux 2.6.16)
4021 pgalloc_normal (since Linux 2.6.5)
4023 pgalloc_high (since Linux 2.6.5)
4025 pgalloc_movable (since Linux 2.6.23)
4027 pgfree (since Linux 2.6.0)
4029 pgactivate (since Linux 2.6.0)
4031 pgdeactivate (since Linux 2.6.0)
4033 pgfault (since Linux 2.6.0)
4035 pgmajfault (since Linux 2.6.0)
4037 pgrefill_dma (since Linux 2.6.5)
4039 pgrefill_dma32 (since Linux 2.6.16)
4041 pgrefill_normal (since Linux 2.6.5)
4043 pgrefill_high (since Linux 2.6.5)
4045 pgrefill_movable (since Linux 2.6.23)
4047 pgsteal_kswapd_dma (since Linux 3.4)
4049 pgsteal_kswapd_dma32 (since Linux 3.4)
4051 pgsteal_kswapd_normal (since Linux 3.4)
4053 pgsteal_kswapd_high (since Linux 3.4)
4055 pgsteal_kswapd_movable (since Linux 3.4)
4057 pgsteal_direct_dma
4059 pgsteal_direct_dma32 (since Linux 3.4)
4061 pgsteal_direct_normal (since Linux 3.4)
4063 pgsteal_direct_high (since Linux 3.4)
4065 pgsteal_direct_movable (since Linux 2.6.23)
4067 pgscan_kswapd_dma
4069 pgscan_kswapd_dma32 (since Linux 2.6.16)
4071 pgscan_kswapd_normal (since Linux 2.6.5)
4073 pgscan_kswapd_high
4075 pgscan_kswapd_movable (since Linux 2.6.23)
4077 pgscan_direct_dma
4079 pgscan_direct_dma32 (since Linux 2.6.16)
4081 pgscan_direct_normal
4083 pgscan_direct_high
4085 pgscan_direct_movable (since Linux 2.6.23)
4087 pgscan_direct_throttle (since Linux 3.6)
4089 zone_reclaim_failed (since linux 2.6.31)
4091 pginodesteal (since linux 2.6.0)
4093 slabs_scanned (since linux 2.6.5)
4095 kswapd_inodesteal (since linux 2.6.0)
4097 kswapd_low_wmark_hit_quickly (since 2.6.33)
4099 kswapd_high_wmark_hit_quickly (since 2.6.33)
4101 pageoutrun (since Linux 2.6.0)
4103 allocstall (since Linux 2.6.0)
4105 pgrotated (since Linux 2.6.0)
4107 drop_pagecache (since Linux 3.15)
4109 drop_slab (since Linux 3.15)
4111 numa_pte_updates (since Linux 3.8)
4113 numa_huge_pte_updates (since Linux 3.13)
4115 numa_hint_faults (since Linux 3.8)
4117 numa_hint_faults_local (since Linux 3.8)
4119 numa_pages_migrated (since Linux 3.8)
4121 pgmigrate_success (since Linux 3.8)
4123 pgmigrate_fail (since Linux 3.8)
4125 compact_migrate_scanned (since Linux 3.8)
4127 compact_free_scanned (since Linux 3.8)
4129 compact_isolated (since Linux 3.8)
4131 compact_stall (since Linux 2.6.35)
4133 See the kernel source file Documentation/vm/tran‐
4134 shuge.txt.
4135 compact_fail (since Linux 2.6.35)
4137 See the kernel source file Documentation/vm/tran‐
4138 shuge.txt.
4139 compact_success (since Linux 2.6.35)
4141 See the kernel source file Documentation/vm/tran‐
4142 shuge.txt.
4143 htlb_buddy_alloc_success (since Linux 2.6.26)
4145 htlb_buddy_alloc_fail (since Linux 2.6.26)
4147 unevictable_pgs_culled (since Linux 2.6.28)
4149 unevictable_pgs_scanned (since Linux 2.6.28)
4151 unevictable_pgs_rescued (since Linux 2.6.28)
4153 unevictable_pgs_mlocked (since Linux 2.6.28)
4155 unevictable_pgs_munlocked (since Linux 2.6.28)
4157 unevictable_pgs_cleared (since Linux 2.6.28)
4159 unevictable_pgs_stranded (since Linux 2.6.28)
4161 thp_fault_alloc (since Linux 2.6.39)
4163 See the kernel source file Documentation/vm/tran‐
4164 shuge.txt.
4165 thp_fault_fallback (since Linux 2.6.39)
4167 See the kernel source file Documentation/vm/tran‐
4168 shuge.txt.
4169 thp_collapse_alloc (since Linux 2.6.39)
4171 See the kernel source file Documentation/vm/tran‐
4172 shuge.txt.
4173 thp_collapse_alloc_failed (since Linux 2.6.39)
4175 See the kernel source file Documentation/vm/tran‐
4176 shuge.txt.
4177 thp_split (since Linux 2.6.39)
4179 See the kernel source file Documentation/vm/tran‐
4180 shuge.txt.
4181 thp_zero_page_alloc (since Linux 3.8)
4183 See the kernel source file Documentation/vm/tran‐
4184 shuge.txt.
4185 thp_zero_page_alloc_failed (since Linux 3.8)
4187 See the kernel source file Documentation/vm/tran‐
4188 shuge.txt.
4189 balloon_inflate (since Linux 3.18)
4191 balloon_deflate (since Linux 3.18)
4193 balloon_migrate (since Linux 3.18)
4195 nr_tlb_remote_flush (since Linux 3.12)
4197 nr_tlb_remote_flush_received (since Linux 3.12)
4199 nr_tlb_local_flush_all (since Linux 3.12)
4201 nr_tlb_local_flush_one (since Linux 3.12)
4203 vmacache_find_calls (since Linux 3.16)
4205 vmacache_find_hits (since Linux 3.16)
4207 vmacache_full_flushes (since Linux 3.19)
4209 /proc/zoneinfo (since Linux 2.6.13)
4211 This file display information about memory zones. This is use‐
4212 ful for analyzing virtual memory behavior.
4213
4215 Many strings (i.e., the environment and command line) are in the inter‐
4216 nal format, with subfields terminated by null bytes ('\0'), so you may
4217 find that things are more readable if you use od -c or tr "\000" "\n"
4218 to read them. Alternatively, echo `cat <file>` works well.
4219 This manual page is incomplete, possibly inaccurate, and is the kind of
4221 thing that needs to be updated very often.
4222
4224 cat(1), dmesg(1), find(1), free(1), init(1), ps(1), tr(1), uptime(1),
4225 chroot(2), mmap(2), readlink(2), syslog(2), slabinfo(5), sysfs(5),
4226 hier(7), namespaces(7), time(7), arp(8), hdparm(8), ifconfig(8),
4227 lsmod(8), lspci(8), mount(8), netstat(8), procinfo(8), route(8),
4228 sysctl(8)
4229 The Linux kernel source files: Documentation/filesystems/proc.txt Docu‐
4231 mentation/sysctl/fs.txt, Documentation/sysctl/kernel.txt, Documenta‐
4232 tion/sysctl/net.txt, and Documentation/sysctl/vm.txt.
4233
4235 This page is part of release 4.15 of the Linux man-pages project. A
4236 description of the project, information about reporting bugs, and the
4237 latest version of this page, can be found at
4238 https://www.kernel.org/doc/man-pages/.
4239Linux 2017-09-15 PROC(5)