1xfs_io(8) System Manager's Manual xfs_io(8)
2
6 xfs_io - debug the I/O path of an XFS filesystem
7
9 xfs_io [ -adfimrRstxT ] [ -c cmd ] ... [ -C cmd ] ... [ -p prog ] [
10 file ]
11 xfs_io -V
12
14 xfs_io is a debugging tool like xfs_db(8), but is aimed at examining
15 the regular file I/O paths rather than the raw XFS volume itself.
16 These code paths include not only the obvious read/write/mmap inter‐
17 faces for manipulating files, but also cover all of the XFS extensions
18 (such as space preallocation, additional inode flags, etc).
19
21 xfs_io commands may be run interactively (the default) or as arguments
22 on the command line. Interactive mode always runs commands on the cur‐
23 rent open file, whilst commands run from the command line may be re‐
24 peated on all open files rather than just the current open file. In
25 general, open file iteration will occur for commands that operate on
26 file content or state. In contrast, commands that operate on filesystem
27 or system-wide state will only be run on the current file regardless of
28 how many files are currently open. Multiple arguments may be given on
29 the command line and they are run in the sequence given. The program
30 exits one all commands have been run.
31 -c cmd Run the specified command on all currently open files. To
33 maintain compatibility with historical usage, commands that
34 can not be run on all open files will still be run but only
35 execute once on the current open file. Multiple -c arguments
36 may be given and may be interleaved on the command line in
37 any order with -C commands.
38 -C cmd Run the specified command only on the current open file.
40 Multiple -C arguments may be given and may be interleaved on
41 the command line in any order with -c commands.
42 -p prog Set the program name for prompts and some error messages, the
44 default value is xfs_io.
45 -f Create file if it does not already exist.
47 -r Open file read-only, initially. This is required if file is
49 immutable or append-only.
50 -i Start an idle thread. The purpose of this idle thread is to
52 test io from a multi threaded process. With single threaded
53 process, the file table is not shared and file structs are
54 not reference counted. Spawning an idle thread can help de‐
55 tecting file struct reference leaks.
56 -x Expert mode. Dangerous commands are only available in this
58 mode. These commands also tend to require additional privi‐
59 leges.
60 -V Prints the version number and exits.
62 The other open(2) options described below are also available from the
64 command line.
65
67 xfs_io maintains a number of open files and memory mappings. Files can
68 be initially opened on the command line (optionally), and additional
69 files can also be opened later.
70 xfs_io commands can be broken up into three groups. Some commands are
72 aimed at doing regular file I/O - read, write, sync, space prealloca‐
73 tion, etc.
74 The second set of commands exist for manipulating memory mapped regions
76 of a file - mapping, accessing, storing, unmapping, flushing, etc.
77 The remaining commands are for the navigation and display of data
79 structures relating to the open files, mappings, and the filesystems
80 where they reside.
81 Many commands have extensive online help. Use the help command for more
83 details on any command.
84
86 file [ N ]
87 Display a list of all open files and (optionally) switch to an
88 alternate current open file.
89 open [[ -acdfrstRTPL ] path ]
91 Closes the current file, and opens the file specified by path
92 instead. Without any arguments, displays statistics about the
93 current file - see the stat command.
94 -a opens append-only (O_APPEND).
95 -d opens for direct I/O (O_DIRECT).
96 -f creates the file if it doesn't already exist (O_CREAT).
97 -r opens read-only (O_RDONLY).
98 -s opens for synchronous I/O (O_SYNC).
99 -t truncates on open (O_TRUNC).
100 -n opens in non-blocking mode if possible (O_NONBLOCK).
101 -T create a temporary file not linked into the filesystem
102 namespace (O_TMPFILE). The pathname passed must refer to
103 a directory which is treated as virtual parent for the
104 newly created invisible file. Can not be used together
105 with the -r option.
106 -R marks the file as a realtime XFS file after opening it,
107 if it is not already marked as such.
108 -P opens the path as a referent only (O_PATH). This is in‐
109 compatible with other flags specifying other O_xxx flags
110 apart from -L.
111 -L doesn't follow symlinks (O_NOFOLLOW). This is incompati‐
112 ble with other flags specifying other O_xxx flags apart
113 from -P.
114 o See the open command.
116 close Closes the current open file, marking the next open file as cur‐
118 rent (if one exists).
119 c See the close command.
121 chmod -r | -w
123 Change the mode of the currently open file. The -r option will
124 set the file permissions to read-only (0444), whilst the -w op‐
125 tion will set the file permissions to read-write (0644). This
126 allows xfs_io to set up mismatches between the file permissions
127 and the open file descriptor read/write mode to exercise permis‐
128 sion checks inside various syscalls.
129 pread [ -b bsize ] [ -qv ] [ -FBR [ -Z seed ] ] [ -V vectors ] offset
131 length
132 Reads a range of bytes in a specified blocksize from the given
133 offset.
134 -b can be used to set the blocksize into which the read(2)
135 requests will be split. The default blocksize is 4096
136 bytes.
137 -q quiet mode, do not write anything to standard output.
138 -v dump the contents of the buffer after reading, by default
139 only the count of bytes actually read is dumped.
140 -F read the buffers in a forward sequential direction.
141 -B read the buffers in a reverse sequential direction.
142 -R read the buffers in the give range in a random order.
143 -Z seed
144 specify the random number seed used for random reads.
145 -V vectors
146 Use the vectored IO read syscall preadv(2) with a number
147 of blocksize length iovecs. The number of iovecs is set
148 by the vectors parameter.
149 r See the pread command.
151 pwrite [ -i file ] [ -qdDwNOW ] [ -s skip ] [ -b size ] [ -S seed ] [
153 -FBR [ -Z zeed ] ] [ -V vectors ] offset length
154 Writes a range of bytes in a specified blocksize from the given
155 offset. The bytes written can be either a set pattern or read
156 in from another file before writing.
157 -i allows an input file to be specified as the source of the
158 data to be written.
159 -q quiet mode, do not write anything to standard output.
160 -d causes direct I/O, rather than the usual buffered I/O, to
161 be used when reading the input file.
162 -w call fdatasync(2) once all writes are complete (included
163 in timing results)
164 -N Perform the pwritev2(2) call with RWF_NOWAIT.
165 -D Perform the pwritev2(2) call with RWF_DSYNC.
166 -O perform pwrite once and return the (maybe partial) bytes
167 written.
168 -W call fsync(2) once all writes are complete (included in
169 timing results)
170 -s specifies the number of bytes to skip from the start of
171 the input file before starting to read.
172 -b used to set the blocksize into which the write(2) re‐
173 quests will be split. The default blocksize is 4096
174 bytes.
175 -S used to set the (repeated) fill pattern which is used
176 when the data to write is not coming from a file. The
177 default buffer fill pattern value is 0xcdcdcdcd.
178 -F write the buffers in a forward sequential direction.
179 -B write the buffers in a reverse sequential direction.
180 -R write the buffers in the give range in a random order.
181 -Z seed
182 specify the random number seed used for random write
183 -V vectors
184 Use the vectored IO write syscall pwritev(2) with a num‐
185 ber of blocksize length iovecs. The number of iovecs is
186 set by the vectors parameter.
187 w See the pwrite command.
189 bmap [ -adelpv ] [ -n nx ]
191 Prints the block mapping for the current open file. Refer to the
192 xfs_bmap(8) manual page for complete documentation.
193 fiemap [ -alv ] [ -n nx ] [ offset [ len ]]
195 Prints the block mapping for the current open file using the
196 fiemap ioctl. Options behave as described in the xfs_bmap(8)
197 manual page.
198 Optionally, this command also supports passing the start offset
200 from where to begin the mapping and the length of that region.
201 The kernel will return any full extents which intersect with the
202 requested range, and the fiemap command will print them in their
203 entirety. If the requested range starts or ends in a hole,
204 fiemap will print the hole, truncated to the requested range.
205 extsize [ -R | -D ] [ value ]
207 Display and/or modify the preferred extent size used when allo‐
208 cating space for the currently open file. If the -R option is
209 specified, a recursive descent is performed for all directory
210 entries below the currently open file (-D can be used to re‐
211 strict the output to directories only). If the target file is a
212 directory, then the inherited extent size is set for that direc‐
213 tory (new files created in that directory inherit that extent
214 size). The value should be specified in bytes, or using one of
215 the usual units suffixes (k, m, g, b, etc). The extent size is
216 always reported in units of bytes.
217 cowextsize [ -R | -D ] [ value ]
219 Display and/or modify the preferred copy-on-write extent size
220 used when allocating space for the currently open file. If the
221 -R option is specified, a recursive descent is performed for all
222 directory entries below the currently open file (-D can be used
223 to restrict the output to directories only). If the target file
224 is a directory, then the inherited CoW extent size is set for
225 that directory (new files created in that directory inherit that
226 CoW extent size). The value should be specified in bytes, or
227 using one of the usual units suffixes (k, m, g, b, etc). The ex‐
228 tent size is always reported in units of bytes.
229 allocsp size 0
231 Sets the size of the file to size and zeroes any additional
232 space allocated using the XFS_IOC_ALLOCSP/XFS_IOC_FREESP system
233 call described in the xfsctl(3) manual page. allocsp and freesp
234 do exactly the same thing.
235 freesp size 0
237 See the allocsp command.
238 fadvise [ -r | -s | [[ -d | -n | -w ] offset length ]]
240 On platforms which support it, allows hints be given to the sys‐
241 tem regarding the expected I/O patterns on the file. The range
242 arguments are required by some advise commands ([*] below), and
243 the others must have no range arguments. With no arguments, the
244 POSIX_FADV_NORMAL advice is implied (default readahead).
245 -d the data will not be accessed again in the near future
246 (POSIX_FADV_DONTNEED[*]).
247 -n data will be accessed once and not be reused
248 (POSIX_FADV_NOREUSE[*]).
249 -r expect access to data in random order (POSIX_FADV_RAN‐
250 DOM), which sets readahead to zero.
251 -s expect access to data in sequential order (POSIX_FADV_SE‐
252 QUENTIAL), which doubles the default readahead on the
253 file.
254 -w advises the specified data will be needed again
255 (POSIX_FADV_WILLNEED[*]) which forces the maximum reada‐
256 head.
257 fdatasync
259 Calls fdatasync(2) to flush the file's in-core data to disk.
260 fsync Calls fsync(2) to flush all in-core file state to disk.
262 s See the fsync command.
264 sync_range [ -a | -b | -w ] offset length
266 On platforms which support it, allows control of syncing a range
267 of the file to disk. With no options, SYNC_FILE_RANGE_WRITE is
268 implied on the range supplied.
269 -a wait for IO in the given range to finish after writing
270 (SYNC_FILE_RANGE_WAIT_AFTER).
271 -b wait for IO in the given range to finish before writing
272 (SYNC_FILE_RANGE_WAIT_BEFORE).
273 -w start writeback of dirty data in the given range
274 (SYNC_FILE_RANGE_WRITE).
275 sync Calls sync(2) to flush all filesystems' in-core data to disk.
277 syncfs Calls syncfs(2) to flush this filesystem's in-core data to disk.
279 resvsp offset length
281 Allocates reserved, unwritten space for part of a file using the
282 XFS_IOC_RESVSP system call described in the xfsctl(3) manual
283 page.
284 unresvsp offset length
286 Frees reserved space for part of a file using the XFS_IOC_UN‐
287 RESVSP system call described in the xfsctl(3) manual page.
288 falloc [ -k ] offset length
290 Allocates reserved, unwritten space for part of a file using the
291 fallocate routine as described in the fallocate(2) manual page.
292 -k will set the FALLOC_FL_KEEP_SIZE flag as described in
293 fallocate(2).
294 fcollapse offset length
296 Call fallocate with FALLOC_FL_COLLAPSE_RANGE flag as described
297 in the fallocate(2) manual page to de-allocates blocks and elim‐
298 inates the hole created in this process by shifting data blocks
299 into the hole.
300 finsert offset length
302 Call fallocate with FALLOC_FL_INSERT_RANGE flag as described in
303 the fallocate(2) manual page to create the hole by shifting data
304 blocks.
305 fpunch offset length
307 Punches (de-allocates) blocks in the file by calling fallocate
308 with the FALLOC_FL_PUNCH_HOLE flag as described in the fallo‐
309 cate(2) manual page.
310 funshare offset length
312 Call fallocate with FALLOC_FL_UNSHARE_RANGE flag as described in
313 the fallocate(2) manual page to unshare all shared blocks within
314 the range.
315 fzero [ -k ] offset length
317 Call fallocate with FALLOC_FL_ZERO_RANGE flag as described in
318 the fallocate(2) manual page to allocate and zero blocks within
319 the range. With the -k option, use the FALLOC_FL_KEEP_SIZE flag
320 as well.
321 zero offset length
323 Call xfsctl with XFS_IOC_ZERO_RANGE as described in the xf‐
324 sctl(3) manual page to allocate and zero blocks within the
325 range.
326 truncate offset
328 Truncates the current file at the given offset using ftrun‐
329 cate(2).
330 sendfile [ -q ] -i srcfile | -f N [ offset length ]
332 On platforms which support it, allows a direct in-kernel copy
333 between two file descriptors. The current open file is the tar‐
334 get, the source must be specified as another open file (-f) or
335 by path (-i).
336 -q quiet mode, do not write anything to standard output.
337 readdir [ -v ] [ -o offset ] [ -l length ]
339 Read a range of directory entries from a given offset of a di‐
340 rectory.
341 -v verbose mode - dump dirent content as defined in read‐
342 dir(3)
343 -o specify starting offset
344 -l specify total length to read (in bytes)
345 seek -a | -d | -h [ -r ] [ -s ] offset
347 On platforms that support the lseek(2) SEEK_DATA and SEEK_HOLE
348 options, display the offsets of the specified segments.
349 -a Display both data and hole segments starting at the spec‐
350 ified offset.
351 -d Display the data segment starting at the specified off‐
352 set.
353 -h Display the hole segment starting at the specified off‐
354 set.
355 -r Recursively display all the specified segments starting
356 at the specified offset.
357 -s Display the starting lseek(2) offset. This offset will be
358 a calculated value when both data and holes are displayed
359 together or performing a recusively display.
360 reflink [ -C ] [ -q ] src_file [src_offset dst_offset length]
362 On filesystems that support the FICLONERANGE or
363 BTRFS_IOC_CLONE_RANGE ioctls, map length bytes at offset
364 dst_offset in the open file to the same physical blocks that are
365 mapped at offset src_offset in the file src_file , replacing any
366 contents that may already have been there. If a program writes
367 into a reflinked block range of either file, the dirty blocks
368 will be cloned, written to, and remapped ("copy on write") in
369 the affected file, leaving the other file(s) unchanged. If
370 src_offset, dst_offset, and length are omitted, all contents of
371 src_file will be reflinked into the open file.
372 -C Print timing statistics in a condensed format.
373 -q Do not print timing statistics at all.
374 dedupe [ -C ] [ -q ] src_file src_offset dst_offset length
376 On filesystems that support the FIDEDUPERANGE or
377 BTRFS_IOC_FILE_EXTENT_SAME ioctls, map length bytes at offset
378 dst_offset in the open file to the same physical blocks that are
379 mapped at offset src_offset in the file src_file , but only if
380 the contents of both ranges are identical. This is known as
381 block-based deduplication. If a program writes into a reflinked
382 block range of either file, the dirty blocks will be cloned,
383 written to, and remapped ("copy on write") in the affected file,
384 leaving the other file(s) unchanged.
385 -C Print timing statistics in a condensed format.
386 -q Do not print timing statistics at all.
387 copy_range [ -s src_offset ] [ -d dst_offset ] [ -l length ] src_file |
389 -f N
390 On filesystems that support the copy_file_range(2) system call,
391 copies data from the source file into the current open file.
392 The source must be specified either by path (src_file) or as an‐
393 other open file (-f). If length is not specified, this command
394 copies data from src_offset to the end of src_file into the
395 dst_file at dst_offset.
396 -s Copy data from src_file beginning from src_offset.
397 -d Copy data into the open file beginning at dst_offset.
398 -l Copy up to length bytes of data.
399 swapext donor_file
401 Swaps extent forks between files. The current open file is the
402 target. The donor file is specified by path. Note that file data
403 is not copied (file content moves with the fork(s)).
404 set_encpolicy [ -c mode ] [ -n mode ] [ -f flags ] [ -v version ] [
406 keyspec ]
407 On filesystems that support encryption, assign an encryption
408 policy to the current file. keyspec is a hex string which spec‐
409 ifies the encryption key to use. For v1 encryption policies,
410 keyspec must be a 16-character hex string (8 bytes). For v2
411 policies, keyspec must be a 32-character hex string (16 bytes).
412 If unspecified, an all-zeroes value is used.
413 -c mode
414 contents encryption mode (e.g. AES-256-XTS)
415 -n mode
416 filenames encryption mode (e.g. AES-256-CTS)
417 -f flags
418 policy flags (numeric)
419 -v version
420 policy version. Defaults to 1 or 2 depending on the
421 length of keyspec; or to 1 if keyspec is unspecified.
422 get_encpolicy [ -1 ] [ -t ]
424 On filesystems that support encryption, display the encryption
425 policy of the current file.
426 -1 Use only the old ioctl to get the encryption policy.
427 This only works if the file has a v1 encryption policy.
428 -t Test whether v2 encryption policies are supported.
429 Prints "supported", "unsupported", or an error message.
430 add_enckey [ -d descriptor ] [ -k key_id ]
432 On filesystems that support encryption, add an encryption key to
433 the filesystem containing the currently open file. By default,
434 the raw key in binary (typically 64 bytes long) is read from
435 standard input.
436 -d descriptor
437 key descriptor, as a 16-character hex string (8 bytes).
438 If given, the key will be available for use by v1 encryp‐
439 tion policies that use this descriptor. Otherwise, the
440 key is added as a v2 policy key, and on success the re‐
441 sulting "key identifier" will be printed.
442 -k key_id
443 ID of kernel keyring key of type "fscrypt-provisioning".
444 If given, the raw key will be taken from here rather than
445 from standard input.
446 rm_enckey [ -a ] keyspec
448 On filesystems that support encryption, remove an encryption key
449 from the filesystem containing the currently open file. keyspec
450 is a hex string specifying the key to remove, as a 16-character
451 "key descriptor" or a 32-character "key identifier".
452 -a Remove the key for all users who have added it, not just
453 the current user. This is a privileged operation.
454 enckey_status keyspec
456 On filesystems that support encryption, display the status of an
457 encryption key. keyspec is a hex string specifying the key for
458 which to display the status, as a 16-character "key descriptor"
459 or a 32-character "key identifier".
460 lsattr [ -R | -D | -a | -v ]
462 List extended inode flags on the currently open file. If the -R
463 option is specified, a recursive descent is performed for all
464 directory entries below the currently open file (-D can be used
465 to restrict the output to directories only). This is a depth
466 first descent, it does not follow symlinks and it also does not
467 cross mount points.
468 The current inode flag letters are documented below. Please re‐
470 fer to the ioctl_xfs_fsgetxattr(2) documentation for more de‐
471 tails about what they mean.
472 r realtime file (XFS_XFLAG_REALTIME)
474 p prealloc (XFS_XFLAG_PREALLOC)
476 i immutable (XFS_XFLAG_IMMUTABLE)
478 a append only (XFS_XFLAG_APPEND)
480 s synchronous file writes (XFS_XFLAG_SYNC)
482 A noatime (XFS_XFLAG_NOATIME)
484 d nodump (XFS_XFLAG_NODUMP)
486 t inherit realtime flag (XFS_XFLAG_RTINHERIT)"
488 P inherit project id (XFS_XFLAG_PROJINHERIT)
490 n no symlink creation (XFS_XFLAG_NOSYMLINKS)
492 e extent size hint (XFS_XFLAG_EXTSIZE)
494 E inherit extent size hint (XFS_XFLAG_EXTSZINHERIT)
496 f nodefrag (XFS_XFLAG_NODEFRAG)
498 S filestream allocator (XFS_XFLAG_FILESTREAM)
500 x direct access persistent memory (XFS_XFLAG_DAX)
502 C copy on write extent hint (XFS_XFLAG_COWEXTSIZE)
504 X has extended attributes (XFS_XFLAG_HASATTR)
506 chattr [ -R | -D ] [ +/-riasAdtPneEfSxC ]
508 Change extended inode flags on the currently open file. The -R
509 and -D options have the same meaning as above.
510 See the lsattr command above for the list of inode flag letters.
512 flink path
514 Link the currently open file descriptor into the filesystem
515 namespace.
516 stat [ -v|-r ]
517 Selected statistics from stat(2) and the XFS_IOC_GETXATTR system
518 call on the current file. If the -v option is specified, the
519 atime (last access), mtime (last modify), and ctime (last
520 change) timestamps are also displayed. The -r option dumps raw
521 fields from the stat structure.
522 statx [ -v|-r ][ -m basic | -m all | -m <mask> ][ -FD ]
523 Selected statistics from stat(2) and the XFS_IOC_GETXATTR system
524 call on the current file.
525 -v Show timestamps.
526 -r Dump raw statx structure values.
527 -m basic
528 Set the field mask for the statx call to STATX_BA‐
529 SIC_STATS.
530 -m all
531 Set the the field mask for the statx call to STATX_ALL
532 (default).
533 -m <mask>
534 Specify a numeric field mask for the statx call.
535 -F Force the attributes to be synced with the server.
536 -D Don't sync attributes with the server.
537 chproj [ -R|-D ]
539 Modifies the project identifier associated with the current
540 path. The -R option will recursively descend if the current path
541 is a directory. The -D option will also recursively descend,
542 only setting modifying projects on subdirectories. See the
543 xfs_quota(8) manual page for more information about project
544 identifiers.
545 lsproj [ -R|-D ]
547 Displays the project identifier associated with the current
548 path. The -R and -D options behave as described above, in ch‐
549 proj.
550 parent [ -cpv ]
552 By default this command prints out the parent inode numbers, in‐
553 ode generation numbers and basenames of all the hardlinks which
554 point to the inode of the current file.
555 -p the output is similar to the default output except path‐
556 names up to the mount-point are printed out instead of
557 the component name.
558 -c the file's filesystem will check all the parent at‐
559 tributes for consistency.
560 -v verbose output will be printed.
561 [NOTE: Not currently operational on Linux.]
562 utimes atime_sec atime_nsec mtime_sec mtime_nsec
564 The utimes command changes the atime and mtime of the current
565 file. sec uses UNIX timestamp notation and is the seconds
566 elapsed since 1970-01-01 00:00:00 UTC. nsec is the nanoseconds
567 since the sec. This value needs to be in the range 0-999999999
568 with UTIME_NOW and UTIME_OMIT being exceptions. Each (sec,
569 nsec) pair constitutes a single timestamp value.
570
574 mmap [ N | [[ -rwxS ] [-s size ] offset length ]]
575 With no arguments, mmap shows the current mappings. Specifying a
576 single numeric argument N sets the current mapping. If two argu‐
577 ments are specified (a range specified by offset and length), a
578 new mapping is created spanning the range, and the protection
579 mode can be given as a combination of PROT_READ (-r), PROT_WRITE
580 (-w), and PROT_EXEC (-x). The mapping will be created with the
581 MAP_SHARED flag by default, or with the Linux specific (MAP_SYNC
582 | MAP_SHARED_VALIDATE) flags if -S is given. -s size is used to
583 do a mmap(size) && munmap(size) operation at first, try to re‐
584 serve some extendible free memory space, if size is bigger than
585 length parameter. But there's not guarantee that the memory af‐
586 ter length ( up to size ) will stay free. e.g. "mmap -rw -s
587 8192 1024" will mmap 0 ~ 1024 bytes memory, but try to reserve
588 1024 ~ 8192 free space(no guarantee). This free space will help‐
589 ful for "mremap 8192" without MREMAP_MAYMOVE flag.
590 mm See the mmap command.
592 mremap [ -f <new_address> ] [ -m ] new_length
594 Changes the current mapping size to new_length. Whether the
595 mapping may be moved is controlled by the flags passed;
596 MREMAP_FIXED (-f), or MREMAP_MAYMOVE (-m). new_length specifies
597 a page-aligned address to which the mapping must be moved. It
598 can be set to 139946004389888, 4096k or 1g etc.
599 mrm See the mremap command.
601 munmap Unmaps the current memory mapping.
603 mu See the munmap command.
605 mread [ -f | -v ] [ -r ] [ offset length ]
607 Accesses a segment of the current memory mapping, optionally
608 dumping it to the standard output stream (with -v or -f option)
609 for inspection. The accesses are performed sequentially from the
610 start offset by default, but can also be done from the end back‐
611 wards through the mapping if the -r option in specified. The
612 two verbose modes differ only in the relative offsets they dis‐
613 play, the -f option is relative to file start, whereas -v shows
614 offsets relative to the start of the mapping.
615 mr See the mread command.
617 mwrite [ -r ] [ -S seed ] [ offset length ]
619 Stores a byte into memory for a range within a mapping. The de‐
620 fault stored value is 'X', repeated to fill the range specified,
621 but this can be changed using the -S option. The memory stores
622 are performed sequentially from the start offset by default, but
623 can also be done from the end backwards through the mapping if
624 the -r option in specified.
625 mw See the mwrite command.
627 msync [ -i ] [ -a | -s ] [ offset length ]
629 Writes all modified copies of pages over the specified range (or
630 entire mapping if no range specified) to their backing storage
631 locations. Also, optionally invalidates (-i) so that subsequent
632 references to the pages will be obtained from their backing
633 storage locations (instead of cached copies). The flush can be
634 done synchronously (-s) or asynchronously (-a).
635 ms See the msync command.
637 madvise [ -d | -r | -s | -w ] [ offset length ]
639 Modifies page cache behavior when operating on the current map‐
640 ping. The range arguments are required by some advise commands
641 ([*] below). With no arguments, the POSIX_MADV_NORMAL advice is
642 implied (default readahead).
643 -d the pages will not be needed (POSIX_MADV_DONTNEED[*]).
644 -r expect random page references (POSIX_MADV_RANDOM), which
645 sets readahead to zero.
646 -s expect sequential page references (POSIX_MADV_SEQUEN‐
647 TIAL), which doubles the default readahead on the file.
648 -w advises the specified pages will be needed again
649 (POSIX_MADV_WILLNEED[*]) which forces the maximum reada‐
650 head.
651 mincore
653 Dumps a list of pages or ranges of pages that are currently in
654 core, for the current memory mapping.
655
658 bulkstat [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s
659 startino ] [ -v version"]
660 Display raw stat information about a bunch of inodes in an XFS
661 filesystem. Options are as follows:
662 -a agno
663 Display only results from the given allocation group.
664 If not specified, all results returned will be dis‐
665 played.
666 -d Print debugging information about call results.
667 -e endino
668 Stop displaying records when this inode number is
669 reached. Defaults to stopping when the system call
670 stops returning results.
671 -n batchsize
672 Retrieve at most this many records per call. Defaults
673 to 4,096.
674 -s startino
675 Display inode allocation records starting with this
676 inode. Defaults to the first inode in the filesystem.
677 If the given inode is not allocated, results will be‐
678 gin with the next allocated inode in the filesystem.
679 -v version
680 Use a particular version of the kernel interface.
681 Currently supported versions are 1 and 5.
682 bulkstat_single [ -d ] [ -v version ] [ inum... | special... ]
684 Display raw stat information about individual inodes in an XFS
685 filesystem. The -d and -v options are the same as the bulkstat
686 command. Arguments must be inode numbers or any of the special
687 values:
688 root Display information about the root directory inode.
689 freeze Suspend all write I/O requests to the filesystem of the current
691 file. Only available in expert mode and requires privileges.
692 thaw Undo the effects of a filesystem freeze operation. Only avail‐
694 able in expert mode and requires privileges.
695 inject [ tag ]
697 Inject errors into a filesystem to observe filesystem behavior
698 at specific points under adverse conditions. Without the tag ar‐
699 gument, displays the list of error tags available. Only avail‐
700 able in expert mode and requires privileges.
701 resblks [ blocks ]
703 Get and/or set count of reserved filesystem blocks using the
704 XFS_IOC_GET_RESBLKS or XFS_IOC_SET_RESBLKS system calls. Note
705 -- this can be useful for exercising out of space behavior.
706 Only available in expert mode and requires privileges.
707 shutdown [ -f ]
709 Force the filesystem to shut down, preventing any further IO.
710 XFS and other filesystems implement this functionality, although
711 implementation details may differ slightly. Only available in
712 expert mode and requires privileges.
713 By default, the filesystem will not attempt to flush completed
715 transactions to disk before shutting down the filesystem. This
716 simulates a disk failure or crash.
717 -f Force the filesystem to flush all completed transactions
718 to disk before shutting down, matching XFS behavior when
719 critical corruption is encountered.
720 statfs Selected statistics from statfs(2) and the XFS_IOC_FSGEOMETRY
722 system call on the filesystem where the current file resides.
723 inode [ [ -n ] number ] [ -v ]
725 The inode command queries physical information about an inode.
726 With no arguments, it will return 1 or 0, indicating whether or
727 not any inode numbers greater than 32 bits are currently in use
728 in the filesystem. If given an inode number as an argument, the
729 command will return the same inode number if it is in use, or 0
730 if not. With -n number , the next used inode number after this
731 number will be returned, or zero if the supplied inode number is
732 the highest one in use. With -v the command will also report the
733 number of bits (32 or 64) used by the inode number printed in
734 the result; if no inode number was specified on the command
735 line, the maximum possible inode number in the system will be
736 printed along with its size.
737 inumbers [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s
739 startino ] [ -v version ]
740 Prints allocation information about groups of inodes in an XFS
741 filesystem. Callers can use this information to figure out
742 which inodes are allocated. Options are as follows:
743 -a agno
744 Display only results from the given allocation group.
745 If not specified, all results returned will be dis‐
746 played.
747 -d Print debugging information about call results.
748 -e endino
749 Stop displaying records when this inode number is
750 reached. Defaults to stopping when the system call
751 stops returning results.
752 -n batchsize
753 Retrieve at most this many records per call. Defaults
754 to 4,096.
755 -s startino
756 Display inode allocation records starting with this
757 inode. Defaults to the first inode in the filesystem.
758 If the given inode is not allocated, results will be‐
759 gin with the next allocated inode in the filesystem.
760 -v version
761 Use a particular version of the kernel interface.
762 Currently supported versions are 1 and 5.
763 scrub type [ agnumber | ino gen ]
765 Scrub internal XFS filesystem metadata. The type parameter
766 specifies which type of metadata to scrub. For AG metadata, one
767 AG number must be specified. For file metadata, the scrub is
768 applied to the open file unless the inode number and generation
769 number are specified.
770 repair type [ agnumber | ino gen ]
772 Repair internal XFS filesystem metadata. The type parameter
773 specifies which type of metadata to repair. For AG metadata,
774 one AG number must be specified. For file metadata, the repair
775 is applied to the open file unless the inode number and genera‐
776 tion number are specified.
777 label [ -c | -s label ]
779 On filesystems that support online label manipulation, get, set,
780 or clear the filesystem label. With no options, print the cur‐
781 rent filesystem label. The -c option clears the filesystem la‐
782 bel by setting it to the null string. The -s label option sets
783 the filesystem label to label. If the label is longer than the
784 filesystem will accept, xfs_io will print an error message. XFS
785 filesystem labels can be at most 12 characters long.
786 fsmap [ -d | -l | -r ] [ -m | -v ] [ -n nx ] [ start ] [ end ]
788 Prints the mapping of disk blocks used by the filesystem hosting
789 the current file. The map lists each extent used by files, al‐
790 location group metadata, journalling logs, and static filesystem
791 metadata, as well as any regions that are unused. Each line of
792 the listings takes the following form:
793 extent: major:minor [startblock..endblock]: owner startoff‐
795 set..endoffset length
796 Static filesystem metadata, allocation group metadata, btrees,
798 journalling logs, and free space are marked by replacing the
799 startoffset..endoffset with the appropriate marker. All blocks,
800 offsets, and lengths are specified in units of 512-byte blocks,
801 no matter what the filesystem's block size is. The optional
802 start and end arguments can be used to constrain the output to a
803 particular range of disk blocks. If these two options are spec‐
804 ified, exactly one of -d, -l, or -r must also be set.
805 -d Display only extents from the data device. This op‐
806 tion only applies for XFS filesystems.
807 -l Display only extents from the external log device.
808 This option only applies to XFS filesystems.
809 -r Display only extents from the realtime device. This
810 option only applies to XFS filesystems.
811 -m Display results in a machine readable format (CSV).
812 This option is not compatible with the -v flag. The
813 columns of the output are: extent number, device ma‐
814 jor, device minor, physical start, physical end,
815 owner, offset start, offset end, length. The start,
816 end, and length numbers are provided in units of 512b.
817 The owner field is a special string that takes the
818 form:
819 inode_%lld_data
821 for inode data.
822 inode_%lld_data_bmbt
823 for inode data extent maps.
824 inode_%lld_attr
825 for inode extended attribute data.
826 inode_%lld_attr_bmbt
827 for inode extended attribute extent maps.
828 special_%u:%u
829 for other filesystem metadata.
830 -n num_extents
833 If this option is given, fsmap obtains the extent list
834 of the file in groups of num_extents extents. In the
835 absence of -n, fsmap queries the system for extents in
836 groups of 131,072 records.
837 -v Shows verbose information. When this flag is speci‐
839 fied, additional AG specific information is appended
840 to each line in the following form:
841 agno (startagblock..endagblock) nblocks flags
843 A second -v option will print out the flags legend.
845 This option is not compatible with the -m flag.
846
850 help [ command ]
851 Display a brief description of one or all commands.
852 print Display a list of all open files and memory mapped regions. The
854 current file and current mapping are distinguishable from any
855 others.
856 p See the print command.
858 quit Exit xfs_io.
860 q See the quit command.
862 log_writes -d device -m mark
864 Create a mark named mark in the dm-log-writes log specified by
865 device. This is intended to be equivalent to the shell command:
866 dmsetup message device 0 mark mark
868 lw See the log_writes command.
870 crc32cselftest
872 Test the internal crc32c implementation to make sure that it
873 computes results correctly.
874
876 mkfs.xfs(8), xfsctl(3), xfs_bmap(8), xfs_db(8), xfs(5), fdatasync(2),
877 fstat(2), fstatfs(2), fsync(2), ftruncate(2), futimens(3), mmap(2),
878 msync(2), open(2), pread(2), pwrite(2), readdir(3), dmsetup(8).
879 xfs_io(8)