1MOUNT(8)                     System Administration                    MOUNT(8)
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NAME

6       mount - mount a filesystem
7

SYNOPSIS

9       mount [-l|-h|-V]
10
11       mount -a [-fFnrsvw] [-t fstype] [-O optlist]
12
13       mount [-fnrsvw] [-o options] device|dir
14
15       mount [-fnrsvw] [-t fstype] [-o options] device dir
16

DESCRIPTION

18       All files accessible in a Unix system are arranged in one big tree, the
19       file hierarchy, rooted at /.  These files can be spread out  over  sev‐
20       eral  devices.  The mount command serves to attach the filesystem found
21       on some device to the big file tree.  Conversely, the umount(8) command
22       will  detach  it  again.  The filesystem is used to control how data is
23       stored on the device or provided in a virtual way by network or another
24       services.
25
26       The standard form of the mount command is:
27
28              mount -t type device dir
29
30       This  tells  the kernel to attach the filesystem found on device (which
31       is of type type) at the directory dir.  The option -t type is optional.
32       The  mount  command  is  usually able to detect a filesystem.  The root
33       permissions are necessary to mount a filesystem by default.   See  sec‐
34       tion  "Non-superuser mounts" below for more details.  The previous con‐
35       tents (if any) and owner and mode of dir become invisible, and as  long
36       as this filesystem remains mounted, the pathname dir refers to the root
37       of the filesystem on device.
38
39       If only the directory or the device is given, for example:
40
41              mount /dir
42
43       then mount looks for a mountpoint (and if not found then for a  device)
44       in  the /etc/fstab file.  It's possible to use the --target or --source
45       options to avoid ambivalent interpretation of the given argument.   For
46       example:
47
48              mount --target /mountpoint
49
50
51       The  same  filesystem  may be mounted more than once, and in some cases
52       (e.g.  network filesystems) the same filesystem maybe be mounted on the
53       same  mountpoint  more  times. The mount command does not implement any
54       policy to control this behavior. All behavior is controlled  by  kernel
55       and  it  is  usually  specific  to  filesystem driver. The exception is
56       --all, in this case already mounted filesystems are ignored (see  --all
57       below for more details).
58
59
60   Listing the mounts
61       The listing mode is maintained for backward compatibility only.
62
63       For  more  robust and customizable output use findmnt(8), especially in
64       your scripts.  Note that control characters in the mountpoint name  are
65       replaced with '?'.
66
67       The following command lists all mounted filesystems (of type type):
68
69              mount [-l] [-t type]
70
71       The option -l adds labels to this listing.  See below.
72
73
74   Indicating the device and filesystem
75       Most  devices  are indicated by a filename (of a block special device),
76       like /dev/sda1, but there are other possibilities.  For example, in the
77       case  of  an  NFS mount, device may look like knuth.cwi.nl:/dir.  It is
78       also possible to indicate a block special device using  its  filesystem
79       label or UUID (see the -L and -U options below), or its partition label
80       or UUID.  Partition identifiers are supported for example for GUID Par‐
81       tition Tables (GPT).
82
83       The  device name of disk partitions are unstable; hardware reconfigura‐
84       tion, adding or removing a device can cause change in  names.  This  is
85       reason  why  it's  strongly  recommended to use filesystem or partition
86       identificators like UUID or LABEL.
87
88       The command lsblk --fs provides overview  of  filesystems,  LABELs  and
89       UUIDs  on  available block devices.  The command blkid -p <device> pro‐
90       vides details about a filesystem on the specified device.
91
92       Don't forget that there is no  guarantee  that  UUIDs  and  labels  are
93       really  unique,  especially if you move, share or copy the device.  Use
94       lsblk -o +UUID,PARTUUID to verify that the UUIDs are really  unique  in
95       your system.
96
97       The  recommended  setup  is  to  use  tags (e.g. UUID=uuid) rather than
98       /dev/disk/by-{label,uuid,partuuid,partlabel}  udev  symlinks   in   the
99       /etc/fstab  file.   Tags  are  more readable, robust and portable.  The
100       mount(8) command internally uses udev symlinks, so the use of  symlinks
101       in  /etc/fstab  has  no advantage over tags.  For more details see lib‐
102       blkid(3).
103
104       Note that mount(8) uses UUIDs as strings.  The UUIDs from  the  command
105       line  or from fstab(5) are not converted to internal binary representa‐
106       tion.  The string representation of the UUID should be based  on  lower
107       case characters.
108
109       The  proc  filesystem is not associated with a special device, and when
110       mounting it, an arbitrary keyword, such as proc can be used instead  of
111       a  device specification.  (The customary choice none is less fortunate:
112       the error message `none already mounted' from mount can be confusing.)
113
114
115   The files /etc/fstab, /etc/mtab and /proc/mounts
116       The file /etc/fstab (see fstab(5)), may contain lines  describing  what
117       devices  are  usually  mounted where, using which options.  The default
118       location of the fstab(5) file can be overridden with the  --fstab  path
119       command-line option (see below for more details).
120
121       The command
122
123              mount -a [-t type] [-O optlist]
124
125       (usually  given  in  a  bootscript) causes all filesystems mentioned in
126       fstab (of the proper type  and/or  having  or  not  having  the  proper
127       options)  to  be mounted as indicated, except for those whose line con‐
128       tains the noauto keyword.  Adding the -F option will make  mount  fork,
129       so that the filesystems are mounted simultaneously.
130
131       When  mounting  a filesystem mentioned in fstab or mtab, it suffices to
132       specify on the command line only the device, or only the mount point.
133
134       The programs mount and umount traditionally maintained a list  of  cur‐
135       rently mounted filesystems in the file /etc/mtab.  The support for reg‐
136       ular classic /etc/mtab  is  completely  disabled  in  compile  time  by
137       default,  because  on  current  Linux systems it is better to make it a
138       symlink to /proc/mounts instead. The regular mtab  file  maintained  in
139       userspace  cannot  reliably  work with namespaces, containers and other
140       advanced Linux features.  If the regular mtab support is  enabled  than
141       it's possible to use the file as well as the symlink.
142
143       If  no arguments are given to mount, the list of mounted filesystems is
144       printed.
145
146       If you want to override mount options from /etc/fstab you have  to  use
147       the -o option:
148
149              mount device|dir -o options
150
151       and  then  the  mount options from the command line will be appended to
152       the list of options from /etc/fstab.  This default behaviour is  possi‐
153       ble  to change by command line option --options-mode.  The usual behav‐
154       ior is that the last option wins if there are conflicting ones.
155
156       The mount program does not read the /etc/fstab file if both device  (or
157       LABEL,  UUID,  PARTUUID or PARTLABEL) and dir are specified.  For exam‐
158       ple, to mount device foo at /dir:
159
160              mount /dev/foo /dir
161
162       This default behaviour is possible to change  by  command  line  option
163       --options-source-force  to  always  read  configuration from fstab. For
164       non-root users mount always read fstab configuration.
165
166
167   Non-superuser mounts
168       Normally, only the superuser  can  mount  filesystems.   However,  when
169       fstab  contains the user option on a line, anybody can mount the corre‐
170       sponding filesystem.
171
172       Thus, given a line
173
174              /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide
175
176       any user can mount the iso9660 filesystem found on  an  inserted  CDROM
177       using the command:
178              mount /cd
179
180       Note that mount is very strict about non-root users and all paths spec‐
181       ified on command line are verified before fstab is parsed or  a  helper
182       program  is  executed.  It's strongly recommended to use a valid mount‐
183       point to specify filesystem, otherwise mount may fail. For example it's
184       bad idea to use NFS or CIFS source on command line.
185
186       For  more details, see fstab(5).  Only the user that mounted a filesys‐
187       tem can unmount it again.  If any user should be able  to  unmount  it,
188       then  use users instead of user in the fstab line.  The owner option is
189       similar to the user option, with the restriction that the user must  be
190       the  owner of the special file.  This may be useful e.g. for /dev/fd if
191       a login script makes the console user owner of this device.  The  group
192       option is similar, with the restriction that the user must be member of
193       the group of the special file.
194
195
196   Bind mount operation
197       Remount part of the file hierarchy somewhere else.  The call is:
198
199              mount --bind olddir newdir
200
201       or by using this fstab entry:
202
203              /olddir /newdir none bind
204
205       After this call the same contents are accessible in two places.
206
207       It is important to understand that "bind" does not to create  any  sec‐
208       ond-class or special node in the kernel VFS. The "bind" is just another
209       operation to attach a filesystem. There is nowhere  stored  information
210       that  the  filesystem has been attached by "bind" operation. The olddir
211       and newdir are independent and the olddir maybe be umounted.
212
213       One can also remount a single file (on a single file).  It's also  pos‐
214       sible  to  use  the  bind  mount  to create a mountpoint from a regular
215       directory, for example:
216
217              mount --bind foo foo
218
219       The bind mount call attaches only (part of) a  single  filesystem,  not
220       possible  submounts.   The entire file hierarchy including submounts is
221       attached a second place by using:
222
223              mount --rbind olddir newdir
224
225       Note that the filesystem mount options maintained by kernel will remain
226       the  same  as  those  on the original mount point.  The userspace mount
227       options (e.g. _netdev) will not be copied by mount(8) and  it's  neces‐
228       sary explicitly specify the options on mount command line.
229
230       mount(8)  since v2.27 allows to change the mount options by passing the
231       relevant options along with --bind.  For example:
232
233              mount -o bind,ro foo foo
234
235       This feature is not supported by the Linux kernel; it is implemented in
236       userspace by an additional mount(2) remounting system call.  This solu‐
237       tion is not atomic.
238
239       The alternative (classic) way to create a read-only bind  mount  is  to
240       use the remount operation, for example:
241
242              mount --bind olddir newdir
243              mount -o remount,bind,ro olddir newdir
244
245       Note  that  a  read-only  bind  will create a read-only mountpoint (VFS
246       entry), but the original filesystem superblock will still be  writable,
247       meaning  that the olddir will be writable, but the newdir will be read-
248       only.
249
250       It's also possible to change nosuid, nodev, noexec, noatime, nodiratime
251       and  relatime VFS entry flags by "remount,bind" operation.  The another
252       (for example filesystem specific flags)  are  silently  ignored.   It's
253       impossible  to  change  mount  options recursively (for example with -o
254       rbind,ro).
255
256       mount(8) since v2.31 ignores the bind flag from /etc/fstab  on  remount
257       operation  (if  "-o remount" specified on command line). This is neces‐
258       sary to fully control mount options on remount by command line. In  the
259       previous  versions  the  bind  flag  has been always applied and it was
260       impossible to re-define mount options without interaction with the bind
261       semantic.  This  mount(8)  behavior  does  not  affect  situations when
262       "remount,bind" is specified in the /etc/fstab file.
263
264
265   The move operation
266       Move a mounted tree to another place (atomically).  The call is:
267
268              mount --move olddir newdir
269
270       This will cause the contents which previously appeared under olddir  to
271       now  be accessible under newdir.  The physical location of the files is
272       not changed.  Note that olddir has to be a mountpoint.
273
274       Note also that moving a mount residing under a shared mount is  invalid
275       and  unsupported.  Use findmnt -o TARGET,PROPAGATION to see the current
276       propagation flags.
277
278
279   Shared subtree operations
280       Since Linux 2.6.15 it is possible to mark a mount and its submounts  as
281       shared,  private,  slave  or  unbindable.   A shared mount provides the
282       ability to create mirrors of that mount such that mounts  and  unmounts
283       within any of the mirrors propagate to the other mirror.  A slave mount
284       receives propagation from its master, but not vice  versa.   A  private
285       mount  carries no propagation abilities.  An unbindable mount is a pri‐
286       vate mount which cannot  be  cloned  through  a  bind  operation.   The
287       detailed  semantics are documented in Documentation/filesystems/shared‐
288       subtree.txt file in the kernel source tree.
289
290       Supported operations are:
291
292              mount --make-shared mountpoint
293              mount --make-slave mountpoint
294              mount --make-private mountpoint
295              mount --make-unbindable mountpoint
296
297       The following commands allow one to recursively change the type of  all
298       the mounts under a given mountpoint.
299
300              mount --make-rshared mountpoint
301              mount --make-rslave mountpoint
302              mount --make-rprivate mountpoint
303              mount --make-runbindable mountpoint
304
305       mount(8) does not read fstab(5) when a --make-* operation is requested.
306       All necessary information has to be specified on the command line.
307
308       Note that the Linux kernel does not allow to change  multiple  propaga‐
309       tion  flags with a single mount(2) system call, and the flags cannot be
310       mixed with other mount options and operations.
311
312       Since util-linux 2.23 the mount command allows to do  more  propagation
313       (topology)  changes  by  one mount(8) call and do it also together with
314       other mount operations.  This feature is EXPERIMENTAL.  The propagation
315       flags  are applied by additional mount(2) system calls when the preced‐
316       ing mount operations were successful.  Note that this use case  is  not
317       atomic.  It is possible to specify the propagation flags in fstab(5) as
318       mount options (private, slave, shared,  unbindable,  rprivate,  rslave,
319       rshared, runbindable).
320
321       For example:
322
323              mount --make-private --make-unbindable /dev/sda1 /foo
324
325       is the same as:
326
327              mount /dev/sda1 /foox
328              mount --make-private /foo
329              mount --make-unbindable /foo
330
331

COMMAND-LINE OPTIONS

333       The  full set of mount options used by an invocation of mount is deter‐
334       mined by first extracting the mount options for the filesystem from the
335       fstab  table,  then  applying any options specified by the -o argument,
336       and finally applying a -r or -w option, when present.
337
338       The command mount  does  not  pass  all  command-line  options  to  the
339       /sbin/mount.suffix  mount helpers.  The interface between mount and the
340       mount helpers is described below in the section EXTERNAL HELPERS.
341
342       Command-line options available for the mount command are:
343
344       -a, --all
345              Mount all filesystems (of the given types)  mentioned  in  fstab
346              (except  for those whose line contains the noauto keyword).  The
347              filesystems are mounted following their  order  in  fstab.   The
348              mount  command  compares  filesystem source, target (and fs root
349              for bind mount or btrfs) to detect already mounted  filesystems.
350              The kernel table with already mounted filesystems is cached dur‐
351              ing mount --all. It means that all duplicated fstab entries will
352              be mounted.
353
354              Note  that it is a bad practice to use mount -a for fstab check‐
355              ing. The recommended solution is findmnt --verify.
356
357       -B, --bind
358              Remount a subtree somewhere  else  (so  that  its  contents  are
359              available in both places).  See above, under Bind mounts.
360
361       -c, --no-canonicalize
362              Don't  canonicalize  paths.  The mount command canonicalizes all
363              paths (from command line or fstab) by default.  This option  can
364              be  used  together  with  the  -f flag for already canonicalized
365              absolute paths.  The option is designed for mount helpers  which
366              call  mount -i.  It is strongly recommended to not use this com‐
367              mand-line option for normal mount operations.
368
369              Note  that  mount(8)  does  not  pass   this   option   to   the
370              /sbin/mount.type helpers.
371
372       -F, --fork
373              (Used  in  conjunction  with -a.)  Fork off a new incarnation of
374              mount for each device.  This will do  the  mounts  on  different
375              devices  or  different  NFS  servers  in parallel.  This has the
376              advantage that it is faster; also NFS timeouts go  in  parallel.
377              A  disadvantage  is that the mounts are done in undefined order.
378              Thus, you cannot use this option if you want to mount both  /usr
379              and /usr/spool.
380
381       -f, --fake
382              Causes  everything to be done except for the actual system call;
383              if it's not obvious, this  ``fakes''  mounting  the  filesystem.
384              This  option is useful in conjunction with the -v flag to deter‐
385              mine what the mount command is trying to do.   It  can  also  be
386              used  to  add entries for devices that were mounted earlier with
387              the -n option.  The -f option checks for an existing  record  in
388              /etc/mtab and fails when the record already exists (with a regu‐
389              lar non-fake mount, this check is done by the kernel).
390
391       -i, --internal-only
392              Don't call the /sbin/mount.filesystem helper even if it exists.
393
394       -L, --label label
395              Mount the partition that has the specified label.
396
397       -l, --show-labels
398              Add the labels in the mount output.  mount must have  permission
399              to  read  the disk device (e.g. be set-user-ID root) for this to
400              work.  One can set such a label for ext2, ext3 or ext4 using the
401              e2label(8)  utility, or for XFS using xfs_admin(8), or for reis‐
402              erfs using reiserfstune(8).
403
404       -M, --move
405              Move a subtree to some other place.  See above,  the  subsection
406              The move operation.
407
408       -n, --no-mtab
409              Mount without writing in /etc/mtab.  This is necessary for exam‐
410              ple when /etc is on a read-only filesystem.
411
412       -N, --namespace ns
413              Perform mount in namespace specified by ns.  ns is either PID of
414              process  running  in that namespace or special file representing
415              that namespace.
416
417              mount(8) switches to the namespace  when  it  reads  /etc/fstab,
418              writes  /etc/mtab  (or  writes to /run/mount) and calls mount(2)
419              system call, otherwise it runs in  the  original  namespace.  It
420              means  that  the  target  namespace does not have to contain any
421              libraries or another requirements necessary to execute  mount(2)
422              command.
423
424              See namespaces(7) for more information.
425
426       -O, --test-opts opts
427              Limit the set of filesystems to which the -a option applies.  In
428              this regard it is like the -t option except that -O  is  useless
429              without -a.  For example, the command:
430
431                     mount -a -O no_netdev
432
433              mounts  all filesystems except those which have the option _net‐
434              dev specified in the options field in the /etc/fstab file.
435
436              It is different from -t in that each option is matched  exactly;
437              a  leading no at the beginning of one option does not negate the
438              rest.
439
440              The -t and -O options are cumulative in  effect;  that  is,  the
441              command
442
443                     mount -a -t ext2 -O _netdev
444
445              mounts  all  ext2  filesystems  with the _netdev option, not all
446              filesystems that are either ext2  or  have  the  _netdev  option
447              specified.
448
449       -o, --options opts
450              Use  the specified mount options.  The opts argument is a comma-
451              separated list.  For example:
452
453                     mount LABEL=mydisk -o noatime,nodev,nosuid
454
455
456              For more details, see the FILESYSTEM-INDEPENDENT  MOUNT  OPTIONS
457              and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
458
459
460       --options-mode mode
461              Controls  how  to  combine  options from fstab/mtab with options
462              from command line.  mode can be one of ignore,  append,  prepend
463              or  replace.   For  example append means that options from fstab
464              are appended to options from command  line.   Default  value  is
465              prepend  --  it  means  command line options are evaluated after
466              fstab options.  Note that the last option wins if there are con‐
467              flicting ones.
468
469
470       --options-source source
471              Source  of  default  options.  source is comma separated list of
472              fstab, mtab and disable.  disable disables fstab  and  mtab  and
473              disables --options-source-force.  Default value is fstab,mtab.
474
475
476       --options-source-force
477              Use  options  from  fstab/mtab  even  if both device and dir are
478              specified.
479
480
481       -R, --rbind
482              Remount a subtree and all possible submounts somewhere else  (so
483              that its contents are available in both places).  See above, the
484              subsection Bind mounts.
485
486       -r, --read-only
487              Mount the filesystem read-only.  A synonym is -o ro.
488
489              Note that, depending on the filesystem type,  state  and  kernel
490              behavior,  the  system may still write to the device.  For exam‐
491              ple, ext3 and ext4 will replay the journal if the filesystem  is
492              dirty.   To  prevent  this kind of write access, you may want to
493              mount an ext3  or  ext4  filesystem  with  the  ro,noload  mount
494              options  or  set  the block device itself to read-only mode, see
495              the blockdev(8) command.
496
497       -s     Tolerate sloppy mount options rather than  failing.   This  will
498              ignore  mount  options  not supported by a filesystem type.  Not
499              all filesystems support this option.  Currently  it's  supported
500              by the mount.nfs mount helper only.
501
502       --source device
503              If  only  one  argument  for the mount command is given then the
504              argument might be interpreted as target (mountpoint)  or  source
505              (device).   This  option  allows  to  explicitly define that the
506              argument is the mount source.
507
508       --target directory
509              If only one argument for the mount command  is  given  then  the
510              argument  might  be interpreted as target (mountpoint) or source
511              (device).  This option allows  to  explicitly  define  that  the
512              argument is the mount target.
513
514       -T, --fstab path
515              Specifies  an  alternative  fstab  file.  If path is a directory
516              then the files in the directory  are  sorted  by  strverscmp(3);
517              files  that  start  with  "." or without an .fstab extension are
518              ignored.  The option can be  specified  more  than  once.   This
519              option  is mostly designed for initramfs or chroot scripts where
520              additional configuration is  specified  beyond  standard  system
521              configuration.
522
523              Note  that  mount(8)  does  not  pass  the option --fstab to the
524              /sbin/mount.type helpers, meaning  that  the  alternative  fstab
525              files will be invisible for the helpers.  This is no problem for
526              normal mounts, but user (non-root) mounts always  require  fstab
527              to verify the user's rights.
528
529       -t, --types fstype
530              The argument following the -t is used to indicate the filesystem
531              type.  The filesystem types which are currently supported depend
532              on  the  running  kernel.   See  /proc/filesystems and /lib/mod‐
533              ules/$(uname -r)/kernel/fs for a complete list of  the  filesys‐
534              tems.   The  most common are ext2, ext3, ext4, xfs, btrfs, vfat,
535              sysfs, proc, nfs and cifs.
536
537              The programs mount and umount support filesystem subtypes.   The
538              subtype   is  defined  by  a  '.subtype'  suffix.   For  example
539              'fuse.sshfs'.  It's recommended to use subtype  notation  rather
540              than   add   any   prefix  to  the  mount  source  (for  example
541              'sshfs#example.com' is deprecated).
542
543              If no -t option is given, or if  the  auto  type  is  specified,
544              mount  will try to guess the desired type.  Mount uses the blkid
545              library for guessing the filesystem type; if that does not  turn
546              up anything that looks familiar, mount will try to read the file
547              /etc/filesystems, or, if that does not exist, /proc/filesystems.
548              All  of  the filesystem types listed there will be tried, except
549              for those that are labeled "nodev" (e.g. devpts, proc and  nfs).
550              If  /etc/filesystems  ends in a line with a single *, mount will
551              read /proc/filesystems afterwards.  While trying, all filesystem
552              types will be mounted with the mount option silent.
553
554              The auto type may be useful for user-mounted floppies.  Creating
555              a file /etc/filesystems can be useful to change the probe  order
556              (e.g.,  to  try vfat before msdos or ext3 before ext2) or if you
557              use a kernel module autoloader.
558
559              More than one type may be specified in a  comma-separated  list,
560              for  option  -t  as well as in an /etc/fstab entry.  The list of
561              filesystem types for option -t can be prefixed with no to  spec‐
562              ify  the  filesystem  types  on which no action should be taken.
563              The prefix no has no effect  when  specified  in  an  /etc/fstab
564              entry.
565
566              The  prefix  no can be meaningful with the -a option.  For exam‐
567              ple, the command
568
569                     mount -a -t nomsdos,smbfs
570
571              mounts all filesystems except those of type msdos and smbfs.
572
573              For most types all the mount program has to do is issue a simple
574              mount(2)  system call, and no detailed knowledge of the filesys‐
575              tem type is required.  For a few types however (like nfs,  nfs4,
576              cifs, smbfs, ncpfs) an ad hoc code is necessary.  The nfs, nfs4,
577              cifs, smbfs, and ncpfs filesystems have a  separate  mount  pro‐
578              gram.  In order to make it possible to treat all types in a uni‐
579              form way, mount will execute the  program  /sbin/mount.type  (if
580              that  exists)  when called with type type.  Since different ver‐
581              sions of the smbmount program  have  different  calling  conven‐
582              tions, /sbin/mount.smbfs may have to be a shell script that sets
583              up the desired call.
584
585       -U, --uuid uuid
586              Mount the partition that has the specified uuid.
587
588       -v, --verbose
589              Verbose mode.
590
591       -w, --rw, --read-write
592              Mount  the  filesystem  read/write.  The  read-write  is  kernel
593              default.  A synonym is -o rw.
594
595              Note  that  specify  -w  on command line forces mount command to
596              never  try  read-only  mount  on  write-protected  devices.  The
597              default  is  try  read-only  if  the previous mount syscall with
598              read-write flags failed.
599
600       -V, --version
601              Display version information and exit.
602
603       -h, --help
604              Display help text and exit.
605
606

FILESYSTEM-INDEPENDENT MOUNT OPTIONS

608       Some of  these  options  are  only  useful  when  they  appear  in  the
609       /etc/fstab file.
610
611       Some  of  these  options could be enabled or disabled by default in the
612       system kernel.  To  check  the  current  setting  see  the  options  in
613       /proc/mounts.   Note that filesystems also have per-filesystem specific
614       default mount options (see for  example  tune2fs  -l  output  for  extN
615       filesystems).
616
617       The  following  options  apply  to any filesystem that is being mounted
618       (but not every filesystem actually honors them – e.g., the sync  option
619       today has an effect only for ext2, ext3, ext4, fat, vfat and ufs):
620
621
622       async  All  I/O  to the filesystem should be done asynchronously.  (See
623              also the sync option.)
624
625       atime  Do not use the noatime feature, so the inode access time is con‐
626              trolled  by  kernel  defaults.  See also the descriptions of the
627              relatime and strictatime mount options.
628
629       noatime
630              Do not update inode access times on this  filesystem  (e.g.  for
631              faster access on the news spool to speed up news servers).  This
632              works for all inode  types  (directories  too),  so  it  implies
633              nodiratime.
634
635       auto   Can be mounted with the -a option.
636
637       noauto Can  only  be  mounted  explicitly (i.e., the -a option will not
638              cause the filesystem to be mounted).
639
640       context=context, fscontext=context, defcontext=context, and
641       rootcontext=context
642              The  context= option is useful when mounting filesystems that do
643              not support extended attributes, such as a floppy or  hard  disk
644              formatted  with  VFAT,  or systems that are not normally running
645              under SELinux, such as an ext3 or ext4 formatted
646
647              disk from a non-SELinux workstation.  You can also use  context=
648              on  filesystems  you  do  not  trust, such as a floppy.  It also
649              helps in compatibility with xattr-supporting filesystems on ear‐
650              lier  2.4.<x> kernel versions.  Even where xattrs are supported,
651              you can save time not having to label every  file  by  assigning
652              the entire disk one security context.
653
654              A    commonly    used    option    for    removable   media   is
655              context="system_u:object_r:removable_t".
656
657              Two other options are fscontext= and defcontext=, both of  which
658              are  mutually  exclusive  of the context option.  This means you
659              can use fscontext and defcontext with each  other,  but  neither
660              can be used with context.
661
662              The  fscontext=  option works for all filesystems, regardless of
663              their xattr support.  The fscontext option sets the  overarching
664              filesystem  label to a specific security context.  This filesys‐
665              tem label is separate from the individual labels on  the  files.
666              It represents the entire filesystem for certain kinds of permis‐
667              sion checks, such as during mount or file creation.   Individual
668              file  labels  are  still  obtained  from the xattrs on the files
669              themselves.  The context option actually sets the aggregate con‐
670              text  that fscontext provides, in addition to supplying the same
671              label for individual files.
672
673              You can set the default security  context  for  unlabeled  files
674              using  defcontext=  option.   This  overrides  the value set for
675              unlabeled files in the policy and  requires  a  filesystem  that
676              supports xattr labeling.
677
678              The  rootcontext= option allows you to explicitly label the root
679              inode of a FS being mounted before that FS or inode becomes vis‐
680              ible  to userspace.  This was found to be useful for things like
681              stateless linux.
682
683              Note that the kernel rejects any remount request  that  includes
684              the  context  option,  even when unchanged from the current con‐
685              text.
686
687              Warning: the context value might contain commas, in  which  case
688              the  value  has  to  be properly quoted, otherwise mount(8) will
689              interpret the comma as a separator between mount options.  Don't
690              forget  that the shell strips off quotes and thus double quoting
691              is required.  For example:
692
693                     mount -t tmpfs none /mnt -o \
694                       'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
695
696              For more details, see selinux(8).
697
698
699       defaults
700              Use the default options: rw, suid, dev, exec, auto, nouser,  and
701              async.
702
703              Note  that  the real set of all default mount options depends on
704              kernel and filesystem type.  See the beginning of  this  section
705              for more details.
706
707       dev    Interpret character or block special devices on the filesystem.
708
709       nodev  Do  not interpret character or block special devices on the file
710              system.
711
712       diratime
713              Update directory inode access times on this filesystem.  This is
714              the default.  (This option is ignored when noatime is set.)
715
716       nodiratime
717              Do  not  update directory inode access times on this filesystem.
718              (This option is implied when noatime is set.)
719
720       dirsync
721              All directory updates within the filesystem should be done  syn‐
722              chronously.   This  affects  the  following system calls: creat,
723              link, unlink, symlink, mkdir, rmdir, mknod and rename.
724
725       exec   Permit execution of binaries.
726
727       noexec Do not permit direct execution of any binaries  on  the  mounted
728              filesystem.
729
730       group  Allow  an  ordinary  user to mount the filesystem if one of that
731              user's groups matches the group  of  the  device.   This  option
732              implies  the options nosuid and nodev (unless overridden by sub‐
733              sequent options, as in the option line group,dev,suid).
734
735       iversion
736              Every time the inode is modified, the i_version  field  will  be
737              incremented.
738
739       noiversion
740              Do not increment the i_version inode field.
741
742       mand   Allow mandatory locks on this filesystem.  See fcntl(2).
743
744       nomand Do not allow mandatory locks on this filesystem.
745
746       _netdev
747              The  filesystem resides on a device that requires network access
748              (used to prevent the  system  from  attempting  to  mount  these
749              filesystems until the network has been enabled on the system).
750
751       nofail Do not report errors for this device if it does not exist.
752
753       relatime
754              Update  inode  access  times  relative to modify or change time.
755              Access time is only updated if the previous access time was ear‐
756              lier  than  the  current  modify  or  change  time.  (Similar to
757              noatime, but it doesn't break mutt or  other  applications  that
758              need  to know if a file has been read since the last time it was
759              modified.)
760
761              Since Linux 2.6.30, the kernel defaults to the behavior provided
762              by   this   option  (unless  noatime  was  specified),  and  the
763              strictatime option is required to obtain traditional  semantics.
764              In  addition, since Linux 2.6.30, the file's last access time is
765              always updated if it is more than 1 day old.
766
767       norelatime
768              Do not use the relatime feature.  See also the strictatime mount
769              option.
770
771       strictatime
772              Allows  to explicitly request full atime updates.  This makes it
773              possible for the kernel to default to relatime  or  noatime  but
774              still  allow  userspace  to override it.  For more details about
775              the default system mount options see /proc/mounts.
776
777       nostrictatime
778              Use the kernel's default behavior for inode access time updates.
779
780       lazytime
781              Only update times (atime, mtime, ctime) on the in-memory version
782              of the file inode.
783
784              This  mount option significantly reduces writes to the inode ta‐
785              ble for workloads that perform frequent random writes to  preal‐
786              located files.
787
788              The on-disk timestamps are updated only when:
789
790              -  the  inode  needs  to be updated for some change unrelated to
791              file timestamps
792
793              - the application employs fsync(2), syncfs(2), or sync(2)
794
795              - an undeleted inode is evicted from memory
796
797              - more than 24 hours have passed since the i-node was written to
798              disk.
799
800
801       nolazytime
802              Do not use the lazytime feature.
803
804       suid   Honor  set-user-ID  and  set-group-ID  bits or file capabilities
805              when executing programs from this filesystem.
806
807       nosuid Do not honor set-user-ID and set-group-ID bits or file capabili‐
808              ties when executing programs from this filesystem.
809
810       silent Turn on the silent flag.
811
812       loud   Turn off the silent flag.
813
814       owner  Allow  an  ordinary user to mount the filesystem if that user is
815              the owner of the device.  This option implies the options nosuid
816              and  nodev  (unless  overridden by subsequent options, as in the
817              option line owner,dev,suid).
818
819       remount
820              Attempt to remount an already-mounted filesystem.  This is  com‐
821              monly  used  to  change  the mount flags for a filesystem, espe‐
822              cially to make a readonly  filesystem  writable.   It  does  not
823              change device or mount point.
824
825              The  remount  operation  together with the bind flag has special
826              semantic. See above, the subsection Bind mounts.
827
828              The remount functionality follows the  standard  way  the  mount
829              command  works  with  options from fstab.  This means that mount
830              does not read fstab (or mtab) only when both device and dir  are
831              specified.
832
833                  mount -o remount,rw /dev/foo /dir
834
835              After this call all old mount options are replaced and arbitrary
836              stuff from fstab (or mtab) is ignored, except the  loop=  option
837              which  is  internally generated and maintained by the mount com‐
838              mand.
839
840                  mount -o remount,rw  /dir
841
842              After this call, mount reads fstab and merges these options with
843              the  options  from  the  command line (-o).  If no mountpoint is
844              found in fstab,  then  a  remount  with  unspecified  source  is
845              allowed.
846
847       ro     Mount the filesystem read-only.
848
849       rw     Mount the filesystem read-write.
850
851       sync   All  I/O to the filesystem should be done synchronously.  In the
852              case of media with a limited number of write cycles  (e.g.  some
853              flash drives), sync may cause life-cycle shortening.
854
855       user   Allow an ordinary user to mount the filesystem.  The name of the
856              mounting user is written to the mtab file  (or  to  the  private
857              libmount  file  in /run/mount on systems without a regular mtab)
858              so that this same user can unmount the filesystem  again.   This
859              option  implies  the  options  noexec, nosuid, and nodev (unless
860              overridden  by  subsequent  options,  as  in  the  option   line
861              user,exec,dev,suid).
862
863       nouser Forbid  an  ordinary  user to mount the filesystem.  This is the
864              default; it does not imply any other options.
865
866       users  Allow any user to mount and to unmount the filesystem, even when
867              some  other  ordinary  user mounted it.  This option implies the
868              options noexec, nosuid, and nodev (unless overridden  by  subse‐
869              quent options, as in the option line users,exec,dev,suid).
870
871       X-*    All options prefixed with "X-" are interpreted as comments or as
872              userspace application-specific options.  These options  are  not
873              stored  in  the  user  space  (e.g.  mtab file), nor sent to the
874              mount.type helpers nor to the mount(2) system  call.   The  sug‐
875              gested format is X-appname.option.
876
877       x-*    The  same  as  X-*  options,  but stored permanently in the user
878              space. It means the options are also  available  for  umount  or
879              another  operations.   Note  that maintain mount options in user
880              space is tricky, because it's necessary use libmount based tools
881              and there is no guarantee that the options will be always avail‐
882              able (for example after a move mount operation  or  in  unshared
883              namespace).
884
885              Note  that before util-linux v2.30 the x-* options have not been
886              maintained by libmount and stored in user  space  (functionality
887              was the same as have X-* now), but due to growing number of use-
888              cases (in initrd, systemd  etc.)  the  functionality  have  been
889              extended  to keep existing fstab configurations usable without a
890              change.
891
892       X-mount.mkdir[=mode]
893              Allow to make a target  directory  (mountpoint).   The  optional
894              argument  mode  specifies  the  filesystem  access mode used for
895              mkdir(2) in octal notation.  The default  mode  is  0755.   This
896              functionality  is  supported only for root users.  The option is
897              also supported as x-mount.mkdir, this notation is deprecated for
898              mount.mkdir since v2.30.
899
900

FILESYSTEM-SPECIFIC MOUNT OPTIONS

902       You  should  consult  the respective man page for the filesystem first.
903       If you want to know what options the  ext4  filesystem  supports,  then
904       check  the ext4(5) man page.  If that doesn't exist, you can also check
905       the corresponding mount page like mount.cifs(8).  Note that  you  might
906       have to install the respective userland tools.
907
908       The  following options apply only to certain filesystems.  We sort them
909       by filesystem.  They all follow the -o flag.
910
911       What options are supported depends a bit on the running  kernel.   More
912       info  may  be  found  in  the  kernel  source  subdirectory  Documenta‐
913       tion/filesystems.
914
915
916   Mount options for adfs
917       uid=value and gid=value
918              Set the owner and group of the files in the filesystem (default:
919              uid=gid=0).
920
921       ownmask=value and othmask=value
922              Set the permission mask for ADFS 'owner' permissions and 'other'
923              permissions,  respectively  (default:  0700  and  0077,  respec‐
924              tively).     See    also   /usr/src/linux/Documentation/filesys‐
925              tems/adfs.txt.
926
927
928   Mount options for affs
929       uid=value and gid=value
930              Set the owner and group of the root of the filesystem  (default:
931              uid=gid=0,  but  with option uid or gid without specified value,
932              the UID and GID of the current process are taken).
933
934       setuid=value and setgid=value
935              Set the owner and group of all files.
936
937       mode=value
938              Set the mode of all files to value & 0777 disregarding the orig‐
939              inal  permissions.   Add  search  permission to directories that
940              have read permission.  The value is given in octal.
941
942       protect
943              Do not allow any changes to the protection bits on the  filesys‐
944              tem.
945
946       usemp  Set UID and GID of the root of the filesystem to the UID and GID
947              of the mount point upon the first sync or umount, and then clear
948              this option.  Strange...
949
950       verbose
951              Print an informational message for each successful mount.
952
953       prefix=string
954              Prefix used before volume name, when following a link.
955
956       volume=string
957              Prefix  (of  length at most 30) used before '/' when following a
958              symbolic link.
959
960       reserved=value
961              (Default: 2.) Number of  unused  blocks  at  the  start  of  the
962              device.
963
964       root=value
965              Give explicitly the location of the root block.
966
967       bs=value
968              Give blocksize.  Allowed values are 512, 1024, 2048, 4096.
969
970       grpquota|noquota|quota|usrquota
971              These  options are accepted but ignored.  (However, quota utili‐
972              ties may react to such strings in /etc/fstab.)
973
974
975   Mount options for debugfs
976       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
977       /sys/kernel/debug.  As of kernel version 3.4, debugfs has the following
978       options:
979
980       uid=n, gid=n
981              Set the owner and group of the mountpoint.
982
983       mode=value
984              Sets the mode of the mountpoint.
985
986
987   Mount options for devpts
988       The devpts filesystem is a pseudo filesystem, traditionally mounted  on
989       /dev/pts.   In  order  to  acquire  a  pseudo terminal, a process opens
990       /dev/ptmx; the number of the pseudo terminal is then made available  to
991       the   process  and  the  pseudo  terminal  slave  can  be  accessed  as
992       /dev/pts/<number>.
993
994       uid=value and gid=value
995              This sets the owner or the group of newly created  PTYs  to  the
996              specified  values.   When nothing is specified, they will be set
997              to the UID and GID of the creating  process.   For  example,  if
998              there  is  a  tty  group with GID 5, then gid=5 will cause newly
999              created PTYs to belong to the tty group.
1000
1001       mode=value
1002              Set the mode of newly created PTYs to the specified value.   The
1003              default  is  0600.  A value of mode=620 and gid=5 makes "mesg y"
1004              the default on newly created PTYs.
1005
1006       newinstance
1007              Create a  private  instance  of  devpts  filesystem,  such  that
1008              indices  of  ptys allocated in this new instance are independent
1009              of indices created in other instances of devpts.
1010
1011              All mounts of devpts without this newinstance option  share  the
1012              same  set  of  pty  indices  (i.e.  legacy mode).  Each mount of
1013              devpts with the newinstance option has  a  private  set  of  pty
1014              indices.
1015
1016              This  option  is  mainly used to support containers in the linux
1017              kernel.  It is implemented in  linux  kernel  versions  starting
1018              with  2.6.29.   Further, this mount option is valid only if CON‐
1019              FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu‐
1020              ration.
1021
1022              To  use  this  option  effectively, /dev/ptmx must be a symbolic
1023              link to pts/ptmx.  See  Documentation/filesystems/devpts.txt  in
1024              the linux kernel source tree for details.
1025
1026       ptmxmode=value
1027
1028              Set the mode for the new ptmx device node in the devpts filesys‐
1029              tem.
1030
1031              With the support for multiple instances of  devpts  (see  newin‐
1032              stance  option  above), each instance has a private ptmx node in
1033              the root of the devpts filesystem (typically /dev/pts/ptmx).
1034
1035              For compatibility with older versions of the kernel, the default
1036              mode  of  the new ptmx node is 0000.  ptmxmode=value specifies a
1037              more useful mode for the ptmx node  and  is  highly  recommended
1038              when the newinstance option is specified.
1039
1040              This  option is only implemented in linux kernel versions start‐
1041              ing with 2.6.29.  Further, this option is  valid  only  if  CON‐
1042              FIG_DEVPTS_MULTIPLE_INSTANCES  is enabled in the kernel configu‐
1043              ration.
1044
1045
1046   Mount options for fat
1047       (Note: fat is not a separate filesystem,  but  a  common  part  of  the
1048       msdos, umsdos and vfat filesystems.)
1049
1050       blocksize={512|1024|2048}
1051              Set blocksize (default 512).  This option is obsolete.
1052
1053       uid=value and gid=value
1054              Set the owner and group of all files.  (Default: the UID and GID
1055              of the current process.)
1056
1057       umask=value
1058              Set the umask (the bitmask  of  the  permissions  that  are  not
1059              present).  The default is the umask of the current process.  The
1060              value is given in octal.
1061
1062       dmask=value
1063              Set the umask applied to directories only.  The default  is  the
1064              umask of the current process.  The value is given in octal.
1065
1066       fmask=value
1067              Set the umask applied to regular files only.  The default is the
1068              umask of the current process.  The value is given in octal.
1069
1070       allow_utime=value
1071              This option controls the permission check of mtime/atime.
1072
1073              20     If current process is in group of file's  group  ID,  you
1074                     can change timestamp.
1075
1076              2      Other users can change timestamp.
1077
1078              The  default  is  set  from `dmask' option. (If the directory is
1079              writable, utime(2) is also allowed.  I.e. ~dmask & 022)
1080
1081              Normally utime(2) checks current process is owner of  the  file,
1082              or  it  has  CAP_FOWNER  capability.  But FAT filesystem doesn't
1083              have UID/GID on disk, so normal check is too  inflexible.   With
1084              this option you can relax it.
1085
1086       check=value
1087              Three different levels of pickiness can be chosen:
1088
1089              r[elaxed]
1090                     Upper  and  lower  case are accepted and equivalent, long
1091                     name  parts  are  truncated   (e.g.   verylongname.foobar
1092                     becomes  verylong.foo),  leading  and embedded spaces are
1093                     accepted in each name part (name and extension).
1094
1095              n[ormal]
1096                     Like "relaxed", but many special  characters  (*,  ?,  <,
1097                     spaces, etc.) are rejected.  This is the default.
1098
1099              s[trict]
1100                     Like  "normal", but names that contain long parts or spe‐
1101                     cial characters that are sometimes used on Linux but  are
1102                     not accepted by MS-DOS (+, =, etc.) are rejected.
1103
1104       codepage=value
1105              Sets  the codepage for converting to shortname characters on FAT
1106              and VFAT filesystems.  By default, codepage 437 is used.
1107
1108       conv=mode
1109              This option is obsolete and may fail or being ignored.
1110
1111       cvf_format=module
1112              Forces the driver to use the CVF (Compressed Volume File) module
1113              cvf_module  instead  of  auto-detection.  If the kernel supports
1114              kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1115              ule loading.  This option is obsolete.
1116
1117       cvf_option=option
1118              Option passed to the CVF module.  This option is obsolete.
1119
1120       debug  Turn on the debug flag.  A version string and a list of filesys‐
1121              tem parameters will be printed (these data are also  printed  if
1122              the parameters appear to be inconsistent).
1123
1124       discard
1125              If  set,  causes discard/TRIM commands to be issued to the block
1126              device when blocks are freed.  This is useful  for  SSD  devices
1127              and sparse/thinly-provisioned LUNs.
1128
1129       dos1xfloppy
1130              If  set,  use a fallback default BIOS Parameter Block configura‐
1131              tion, determined by backing device size.  These  static  parame‐
1132              ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1133              kiB, and 360 kiB floppies and floppy images.
1134
1135       errors={panic|continue|remount-ro}
1136              Specify FAT behavior on critical errors: panic, continue without
1137              doing  anything,  or  remount  the  partition  in read-only mode
1138              (default behavior).
1139
1140       fat={12|16|32}
1141              Specify a 12, 16 or 32 bit fat.  This  overrides  the  automatic
1142              FAT type detection routine.  Use with caution!
1143
1144       iocharset=value
1145              Character set to use for converting between 8 bit characters and
1146              16 bit Unicode characters.   The  default  is  iso8859-1.   Long
1147              filenames are stored on disk in Unicode format.
1148
1149       nfs={stale_rw|nostale_ro}
1150              Enable  this  only if you want to export the FAT filesystem over
1151              NFS.
1152
1153              stale_rw: This option maintains an index  (cache)  of  directory
1154              inodes  which  is  used by the nfs-related code to improve look-
1155              ups.  Full file operations (read/write) over NFS  are  supported
1156              but with cache eviction at NFS server, this could result in spu‐
1157              rious ESTALE errors.
1158
1159              nostale_ro: This option bases the inode number and  file  handle
1160              on  the  on-disk  location of a file in the FAT directory entry.
1161              This ensures that ESTALE will not be returned after  a  file  is
1162              evicted from the inode cache.  However, it means that operations
1163              such as rename, create and unlink could cause file handles  that
1164              previously  pointed  at  one  file to point at a different file,
1165              potentially causing data  corruption.   For  this  reason,  this
1166              option also mounts the filesystem readonly.
1167
1168              To  maintain  backward compatibility, '-o nfs' is also accepted,
1169              defaulting to stale_rw.
1170
1171       tz=UTC This option disables the conversion of timestamps between  local
1172              time  (as  used  by  Windows  on  FAT) and UTC (which Linux uses
1173              internally).  This is particularly useful when mounting  devices
1174              (like digital cameras) that are set to UTC in order to avoid the
1175              pitfalls of local time.
1176
1177       time_offset=minutes
1178              Set offset for conversion of timestamps from local time used  by
1179              FAT  to  UTC.   I.e., minutes will be subtracted from each time‐
1180              stamp to convert it to UTC used internally by  Linux.   This  is
1181              useful  when the time zone set in the kernel via settimeofday(2)
1182              is not the time zone used by the  filesystem.   Note  that  this
1183              option  still  does not provide correct time stamps in all cases
1184              in presence of DST - time stamps in a different DST setting will
1185              be off by one hour.
1186
1187       quiet  Turn on the quiet flag.  Attempts to chown or chmod files do not
1188              return errors, although they fail.  Use with caution!
1189
1190       rodir  FAT has the ATTR_RO  (read-only)  attribute.   On  Windows,  the
1191              ATTR_RO  of the directory will just be ignored, and is used only
1192              by applications as a flag (e.g.  it's  set  for  the  customized
1193              folder).
1194
1195              If you want to use ATTR_RO as read-only flag even for the direc‐
1196              tory, set this option.
1197
1198       showexec
1199              If set, the execute permission bits of the file will be  allowed
1200              only  if  the extension part of the name is .EXE, .COM, or .BAT.
1201              Not set by default.
1202
1203       sys_immutable
1204              If set, ATTR_SYS attribute on FAT is handled as  IMMUTABLE  flag
1205              on Linux.  Not set by default.
1206
1207       flush  If set, the filesystem will try to flush to disk more early than
1208              normal.  Not set by default.
1209
1210       usefree
1211              Use the "free clusters" value stored on FSINFO.  It'll  be  used
1212              to determine number of free clusters without scanning disk.  But
1213              it's not used by default, because recent Windows don't update it
1214              correctly  in some case.  If you are sure the "free clusters" on
1215              FSINFO is correct, by this option you can avoid scanning disk.
1216
1217       dots, nodots, dotsOK=[yes|no]
1218              Various misguided attempts to force Unix or DOS conventions onto
1219              a FAT filesystem.
1220
1221
1222   Mount options for hfs
1223       creator=cccc, type=cccc
1224              Set  the  creator/type  values as shown by the MacOS finder used
1225              for creating new files.  Default values: '????'.
1226
1227       uid=n, gid=n
1228              Set the owner and group of all files.  (Default: the UID and GID
1229              of the current process.)
1230
1231       dir_umask=n, file_umask=n, umask=n
1232              Set  the  umask  used for all directories, all regular files, or
1233              all files and directories.  Defaults to the umask of the current
1234              process.
1235
1236       session=n
1237              Select  the  CDROM  session  to mount.  Defaults to leaving that
1238              decision to the CDROM driver.  This option will fail  with  any‐
1239              thing but a CDROM as underlying device.
1240
1241       part=n Select partition number n from the device.  Only makes sense for
1242              CDROMs.  Defaults to not parsing the partition table at all.
1243
1244       quiet  Don't complain about invalid mount options.
1245
1246
1247   Mount options for hpfs
1248       uid=value and gid=value
1249              Set the owner and group of all files. (Default: the UID and  GID
1250              of the current process.)
1251
1252       umask=value
1253              Set  the  umask  (the  bitmask  of  the permissions that are not
1254              present).  The default is the umask of the current process.  The
1255              value is given in octal.
1256
1257       case={lower|asis}
1258              Convert all files names to lower case, or leave them.  (Default:
1259              case=lower.)
1260
1261       conv=mode
1262              This option is obsolete and may fail or being ignored.
1263
1264       nocheck
1265              Do not abort mounting when certain consistency checks fail.
1266
1267
1268   Mount options for iso9660
1269       ISO 9660 is a standard describing a filesystem structure to be used  on
1270       CD-ROMs. (This filesystem type is also seen on some DVDs.  See also the
1271       udf filesystem.)
1272
1273       Normal iso9660 filenames  appear  in  an  8.3  format  (i.e.,  DOS-like
1274       restrictions on filename length), and in addition all characters are in
1275       upper case.  Also there is no field  for  file  ownership,  protection,
1276       number of links, provision for block/character devices, etc.
1277
1278       Rock  Ridge is an extension to iso9660 that provides all of these UNIX-
1279       like features.  Basically there are extensions to each directory record
1280       that  supply  all of the additional information, and when Rock Ridge is
1281       in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1282       tem (except that it is read-only, of course).
1283
1284       norock Disable  the  use  of  Rock Ridge extensions, even if available.
1285              Cf. map.
1286
1287       nojoliet
1288              Disable the use of Microsoft Joliet extensions, even  if  avail‐
1289              able.  Cf. map.
1290
1291       check={r[elaxed]|s[trict]}
1292              With  check=relaxed, a filename is first converted to lower case
1293              before doing the  lookup.   This  is  probably  only  meaningful
1294              together with norock and map=normal.  (Default: check=strict.)
1295
1296       uid=value and gid=value
1297              Give all files in the filesystem the indicated user or group id,
1298              possibly overriding the information  found  in  the  Rock  Ridge
1299              extensions.  (Default: uid=0,gid=0.)
1300
1301       map={n[ormal]|o[ff]|a[corn]}
1302              For  non-Rock  Ridge volumes, normal name translation maps upper
1303              to lower case ASCII, drops a trailing `;1', and converts `;'  to
1304              `.'.   With  map=off  no  name translation is done.  See norock.
1305              (Default: map=normal.)  map=acorn is like  map=normal  but  also
1306              apply Acorn extensions if present.
1307
1308       mode=value
1309              For  non-Rock  Ridge volumes, give all files the indicated mode.
1310              (Default: read and execute  permission  for  everybody.)   Octal
1311              mode values require a leading 0.
1312
1313       unhide Also  show  hidden and associated files.  (If the ordinary files
1314              and the associated or hidden files have the same filenames, this
1315              may make the ordinary files inaccessible.)
1316
1317       block={512|1024|2048}
1318              Set   the   block   size  to  the  indicated  value.   (Default:
1319              block=1024.)
1320
1321       conv=mode
1322              This option is obsolete and may fail or being ignored.
1323
1324       cruft  If the high byte of the file length contains other garbage,  set
1325              this  mount  option  to  ignore  the high order bits of the file
1326              length.  This implies that a file cannot be larger than 16 MB.
1327
1328       session=x
1329              Select number of session on multisession CD.
1330
1331       sbsector=xxx
1332              Session begins from sector xxx.
1333
1334       The following options are the same as for vfat and specifying them only
1335       makes  sense  when  using discs encoded using Microsoft's Joliet exten‐
1336       sions.
1337
1338       iocharset=value
1339              Character set to use for converting 16 bit Unicode characters on
1340              CD to 8 bit characters.  The default is iso8859-1.
1341
1342       utf8   Convert 16 bit Unicode characters on CD to UTF-8.
1343
1344
1345   Mount options for jfs
1346       iocharset=name
1347              Character  set to use for converting from Unicode to ASCII.  The
1348              default is to do no conversion.   Use  iocharset=utf8  for  UTF8
1349              translations.   This  requires  CONFIG_NLS_UTF8 to be set in the
1350              kernel .config file.
1351
1352       resize=value
1353              Resize the volume to value blocks.  JFS only supports growing  a
1354              volume,  not  shrinking  it.  This option is only valid during a
1355              remount, when the volume is mounted read-write.  The resize key‐
1356              word  with no value will grow the volume to the full size of the
1357              partition.
1358
1359       nointegrity
1360              Do not write to the journal.  The primary use of this option  is
1361              to  allow  for  higher  performance when restoring a volume from
1362              backup media.  The integrity of the volume is not guaranteed  if
1363              the system abnormally ends.
1364
1365       integrity
1366              Default.   Commit  metadata  changes  to  the journal.  Use this
1367              option to remount a volume where the nointegrity option was pre‐
1368              viously specified in order to restore normal behavior.
1369
1370       errors={continue|remount-ro|panic}
1371              Define  the  behavior  when  an  error  is encountered.  (Either
1372              ignore errors and just mark the filesystem  erroneous  and  con‐
1373              tinue,  or  remount  the filesystem read-only, or panic and halt
1374              the system.)
1375
1376       noquota|quota|usrquota|grpquota
1377              These options are accepted but ignored.
1378
1379
1380   Mount options for msdos
1381       See mount options for fat.  If the msdos filesystem detects  an  incon‐
1382       sistency,  it reports an error and sets the file system read-only.  The
1383       filesystem can be made writable again by remounting it.
1384
1385
1386   Mount options for ncpfs
1387       Just like nfs, the ncpfs implementation expects a  binary  argument  (a
1388       struct ncp_mount_data) to the mount system call.  This argument is con‐
1389       structed by ncpmount(8) and the current version of  mount  (2.12)  does
1390       not know anything about ncpfs.
1391
1392
1393   Mount options for ntfs
1394       iocharset=name
1395              Character  set  to  use when returning file names.  Unlike VFAT,
1396              NTFS suppresses names that  contain  nonconvertible  characters.
1397              Deprecated.
1398
1399       nls=name
1400              New name for the option earlier called iocharset.
1401
1402       utf8   Use UTF-8 for converting file names.
1403
1404       uni_xlate={0|1|2}
1405              For  0  (or  `no'  or  `false'), do not use escape sequences for
1406              unknown Unicode characters.  For 1 (or `yes' or  `true')  or  2,
1407              use  vfat-style 4-byte escape sequences starting with ":".  Here
1408              2 give a little-endian encoding and 1  a  byteswapped  bigendian
1409              encoding.
1410
1411       posix=[0|1]
1412              If enabled (posix=1), the filesystem distinguishes between upper
1413              and lower case.  The 8.3 alias names are presented as hard links
1414              instead of being suppressed.  This option is obsolete.
1415
1416       uid=value, gid=value and umask=value
1417              Set  the  file permission on the filesystem.  The umask value is
1418              given in octal.  By default, the files are owned by root and not
1419              readable by somebody else.
1420
1421
1422   Mount options for overlay
1423       Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1424       for other filesystems.
1425
1426       An overlay filesystem combines two filesystems -  an  upper  filesystem
1427       and  a  lower  filesystem.  When a name exists in both filesystems, the
1428       object in the upper filesystem is visible while the object in the lower
1429       filesystem is either hidden or, in the case of directories, merged with
1430       the upper object.
1431
1432       The lower filesystem can be any filesystem supported by Linux and  does
1433       not  need  to  be  writable.   The lower filesystem can even be another
1434       overlayfs.  The upper filesystem will normally be writable and if it is
1435       it must support the creation of trusted.* extended attributes, and must
1436       provide a valid d_type in readdir responses, so NFS is not suitable.
1437
1438       A read-only overlay of two read-only filesystems may use any filesystem
1439       type.   The  options  lowerdir  and upperdir are combined into a merged
1440       directory by using:
1441
1442              mount -t overlay  overlay  \
1443                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged
1444
1445
1446       lowerdir=directory
1447              Any filesystem, does not need to be on a writable filesystem.
1448
1449       upperdir=directory
1450              The upperdir is normally on a writable filesystem.
1451
1452       workdir=directory
1453              The workdir needs to be an empty directory on the same  filesys‐
1454              tem as upperdir.
1455
1456
1457   Mount options for reiserfs
1458       Reiserfs is a journaling filesystem.
1459
1460       conv   Instructs  version  3.6 reiserfs software to mount a version 3.5
1461              filesystem, using the 3.6  format  for  newly  created  objects.
1462              This  filesystem  will no longer be compatible with reiserfs 3.5
1463              tools.
1464
1465       hash={rupasov|tea|r5|detect}
1466              Choose which hash function  reiserfs  will  use  to  find  files
1467              within directories.
1468
1469              rupasov
1470                     A hash invented by Yury Yu. Rupasov.  It is fast and pre‐
1471                     serves locality,  mapping  lexicographically  close  file
1472                     names  to  close  hash values.  This option should not be
1473                     used, as it causes a high probability of hash collisions.
1474
1475              tea    A   Davis-Meyer   function    implemented    by    Jeremy
1476                     Fitzhardinge.   It  uses hash permuting bits in the name.
1477                     It gets high randomness and, therefore,  low  probability
1478                     of hash collisions at some CPU cost.  This may be used if
1479                     EHASHCOLLISION errors are experienced with the r5 hash.
1480
1481              r5     A modified version of the rupasov hash.  It  is  used  by
1482                     default  and is the best choice unless the filesystem has
1483                     huge directories and unusual file-name patterns.
1484
1485              detect Instructs mount to detect which hash function is  in  use
1486                     by  examining  the filesystem being mounted, and to write
1487                     this information into the reiserfs superblock.   This  is
1488                     only  useful on the first mount of an old format filesys‐
1489                     tem.
1490
1491       hashed_relocation
1492              Tunes  the  block  allocator.   This  may  provide   performance
1493              improvements in some situations.
1494
1495       no_unhashed_relocation
1496              Tunes   the  block  allocator.   This  may  provide  performance
1497              improvements in some situations.
1498
1499       noborder
1500              Disable the border allocator  algorithm  invented  by  Yury  Yu.
1501              Rupasov.  This may provide performance improvements in some sit‐
1502              uations.
1503
1504       nolog  Disable  journaling.   This  will  provide  slight   performance
1505              improvements in some situations at the cost of losing reiserfs's
1506              fast recovery from crashes.  Even with this  option  turned  on,
1507              reiserfs  still  performs  all  journaling  operations, save for
1508              actual writes into its journaling area.  Implementation of nolog
1509              is a work in progress.
1510
1511       notail By  default,  reiserfs  stores  small  files  and  `file  tails'
1512              directly into its tree.  This confuses some  utilities  such  as
1513              LILO(8).   This  option is used to disable packing of files into
1514              the tree.
1515
1516       replayonly
1517              Replay the transactions which are in the  journal,  but  do  not
1518              actually mount the filesystem.  Mainly used by reiserfsck.
1519
1520       resize=number
1521              A remount option which permits online expansion of reiserfs par‐
1522              titions.  Instructs reiserfs to assume that the device has  num‐
1523              ber  blocks.  This option is designed for use with devices which
1524              are under logical volume management (LVM).  There is  a  special
1525              resizer     utility     which     can     be    obtained    from
1526              ftp://ftp.namesys.com/pub/reiserfsprogs.
1527
1528       user_xattr
1529              Enable Extended User Attributes.  See the attr(5) manual page.
1530
1531       acl    Enable POSIX Access Control Lists.  See the acl(5) manual page.
1532
1533       barrier=none / barrier=flush
1534              This disables / enables the use of write barriers in  the  jour‐
1535              naling   code.   barrier=none  disables,  barrier=flush  enables
1536              (default).  This also requires an IO  stack  which  can  support
1537              barriers,  and  if reiserfs gets an error on a barrier write, it
1538              will disable barriers again  with  a  warning.   Write  barriers
1539              enforce  proper  on-disk  ordering  of  journal  commits, making
1540              volatile disk write caches safe  to  use,  at  some  performance
1541              penalty.   If  your  disks  are  battery-backed  in  one  way or
1542              another, disabling barriers may safely improve performance.
1543
1544
1545   Mount options for ubifs
1546       UBIFS is a flash filesystem which works on top of  UBI  volumes.   Note
1547       that atime is not supported and is always turned off.
1548
1549       The device name may be specified as
1550              ubiX_Y UBI device number X, volume number Y
1551
1552              ubiY   UBI device number 0, volume number Y
1553
1554              ubiX:NAME
1555                     UBI device number X, volume with name NAME
1556
1557              ubi:NAME
1558                     UBI device number 0, volume with name NAME
1559       Alternative !  separator may be used instead of :.
1560
1561       The following mount options are available:
1562
1563       bulk_read
1564              Enable  bulk-read.   VFS read-ahead is disabled because it slows
1565              down the file system.  Bulk-Read is  an  internal  optimization.
1566              Some  flashes  may  read  faster if the data are read at one go,
1567              rather than at several read requests.  For example, OneNAND  can
1568              do "read-while-load" if it reads more than one NAND page.
1569
1570       no_bulk_read
1571              Do not bulk-read.  This is the default.
1572
1573       chk_data_crc
1574              Check data CRC-32 checksums.  This is the default.
1575
1576       no_chk_data_crc.
1577              Do  not  check  data  CRC-32  checksums.   With this option, the
1578              filesystem does not check CRC-32 checksum for data, but it  does
1579              check  it  for  the  internal indexing information.  This option
1580              only affects reading, not writing.  CRC-32 is always  calculated
1581              when writing the data.
1582
1583       compr={none|lzo|zlib}
1584              Select  the  default compressor which is used when new files are
1585              written.  It is still  possible  to  read  compressed  files  if
1586              mounted with the none option.
1587
1588
1589   Mount options for udf
1590       UDF  is  the  "Universal  Disk  Format" filesystem defined by OSTA, the
1591       Optical Storage Technology Association, and is often used for  DVD-ROM,
1592       frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1593       ever, perfectly usable by itself on disk drives, flash drives and other
1594       block devices.  See also iso9660.
1595
1596       uid=   Make  all  files  in  the  filesystem  belong to the given user.
1597              uid=forget can be specified  independently  of  (or  usually  in
1598              addition  to)  uid=<user> and results in UDF not storing uids to
1599              the media. In fact the recorded uid is the 32-bit  overflow  uid
1600              -1 as defined by the UDF standard.  The value is given as either
1601              <user> which is a valid user name or the  corresponding  decimal
1602              user id, or the special string "forget".
1603
1604       gid=   Make  all  files  in  the  filesystem belong to the given group.
1605              gid=forget can be specified  independently  of  (or  usually  in
1606              addition  to) gid=<group> and results in UDF not storing gids to
1607              the media. In fact the recorded gid is the 32-bit  overflow  gid
1608              -1 as defined by the UDF standard.  The value is given as either
1609              <group> which is a valid group name or the corresponding decimal
1610              group id, or the special string "forget".
1611
1612       umask= Mask  out  the  given  permissions from all inodes read from the
1613              filesystem.  The value is given in octal.
1614
1615       mode=  If mode= is set the permissions of all non-directory inodes read
1616              from  the filesystem will be set to the given mode. The value is
1617              given in octal.
1618
1619       dmode= If dmode= is set the permissions of all  directory  inodes  read
1620              from the filesystem will be set to the given dmode. The value is
1621              given in octal.
1622
1623       bs=    Set the block size. Default value prior to kernel version 2.6.30
1624              was  2048.  Since 2.6.30 and prior to 4.11 it was logical device
1625              block size with fallback to 2048. Since 4.11 it is logical block
1626              size  with  fallback  to  any  valid  block size between logical
1627              device block size and 4096.
1628
1629              For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1630              PATIBILITY and BLOCK SIZE.
1631
1632       unhide Show otherwise hidden files.
1633
1634       undelete
1635              Show deleted files in lists.
1636
1637       adinicb
1638              Embed data in the inode. (default)
1639
1640       noadinicb
1641              Don't embed data in the inode.
1642
1643       shortad
1644              Use short UDF address descriptors.
1645
1646       longad Use long UDF address descriptors. (default)
1647
1648       nostrict
1649              Unset strict conformance.
1650
1651       iocharset=
1652              Set  the  NLS  character set. This requires kernel compiled with
1653              CONFIG_UDF_NLS option.
1654
1655       utf8   Set the UTF-8 character set.
1656
1657   Mount options for debugging and disaster recovery
1658       novrs  Ignore the Volume Recognition Sequence and attempt to mount any‐
1659              way.
1660
1661       session=
1662              Select  the  session  number  for multi-session recorded optical
1663              media. (default= last session)
1664
1665       anchor=
1666              Override standard anchor location. (default= 256)
1667
1668       lastblock=
1669              Set the last block of the filesystem.
1670
1671   Unused historical mount options that  may  be  encountered  and  should  be
1672       removed
1673       uid=ignore
1674              Ignored, use uid=<user> instead.
1675
1676       gid=ignore
1677              Ignored, use gid=<group> instead.
1678
1679       volume=
1680              Unimplemented and ignored.
1681
1682       partition=
1683              Unimplemented and ignored.
1684
1685       fileset=
1686              Unimplemented and ignored.
1687
1688       rootdir=
1689              Unimplemented and ignored.
1690
1691
1692   Mount options for ufs
1693       ufstype=value
1694              UFS  is a filesystem widely used in different operating systems.
1695              The problem are differences among implementations.  Features  of
1696              some  implementations are undocumented, so its hard to recognize
1697              the type of ufs automatically.  That's why the user must specify
1698              the type of ufs by mount option.  Possible values are:
1699
1700              old    Old  format  of  ufs,  this  is  the  default, read only.
1701                     (Don't forget to give the -r option.)
1702
1703              44bsd  For filesystems created by  a  BSD-like  system  (NetBSD,
1704                     FreeBSD, OpenBSD).
1705
1706              ufs2   Used in FreeBSD 5.x supported as read-write.
1707
1708              5xbsd  Synonym for ufs2.
1709
1710              sun    For filesystems created by SunOS or Solaris on Sparc.
1711
1712              sunx86 For filesystems created by Solaris on x86.
1713
1714              hp     For filesystems created by HP-UX, read-only.
1715
1716              nextstep
1717                     For  filesystems  created  by  NeXTStep (on NeXT station)
1718                     (currently read only).
1719
1720              nextstep-cd
1721                     For NextStep CDROMs (block_size == 2048), read-only.
1722
1723              openstep
1724                     For  filesystems  created  by  OpenStep  (currently  read
1725                     only).   The  same filesystem type is also used by Mac OS
1726                     X.
1727
1728
1729       onerror=value
1730              Set behavior on error:
1731
1732              panic  If an error is encountered, cause a kernel panic.
1733
1734              [lock|umount|repair]
1735                     These mount options don't do anything at present; when an
1736                     error is encountered only a console message is printed.
1737
1738
1739   Mount options for umsdos
1740       See mount options for msdos.  The dotsOK option is explicitly killed by
1741       umsdos.
1742
1743
1744   Mount options for vfat
1745       First of all, the mount options for fat  are  recognized.   The  dotsOK
1746       option is explicitly killed by vfat.  Furthermore, there are
1747
1748       uni_xlate
1749              Translate   unhandled  Unicode  characters  to  special  escaped
1750              sequences.  This lets you backup and restore filenames that  are
1751              created with any Unicode characters.  Without this option, a '?'
1752              is used when no translation is possible.  The  escape  character
1753              is  ':'  because it is otherwise invalid on the vfat filesystem.
1754              The escape sequence that gets used, where u is the Unicode char‐
1755              acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1756
1757       posix  Allow  two  files  with  names  that  only differ in case.  This
1758              option is obsolete.
1759
1760       nonumtail
1761              First try to make a short name without sequence  number,  before
1762              trying name~num.ext.
1763
1764       utf8   UTF8  is  the  filesystem safe 8-bit encoding of Unicode that is
1765              used by the console.  It can be enabled for the filesystem  with
1766              this  option or disabled with utf8=0, utf8=no or utf8=false.  If
1767              `uni_xlate' gets set, UTF8 gets disabled.
1768
1769       shortname=mode
1770              Defines the behavior for creation and display of filenames which
1771              fit  into  8.3 characters.  If a long name for a file exists, it
1772              will always be the preferred one for display.   There  are  four
1773              modes:
1774
1775              lower  Force  the short name to lower case upon display; store a
1776                     long name when the short name is not all upper case.
1777
1778              win95  Force the short name to upper case upon display; store  a
1779                     long name when the short name is not all upper case.
1780
1781              winnt  Display  the short name as is; store a long name when the
1782                     short name is not all lower case or all upper case.
1783
1784              mixed  Display the short name as is; store a long name when  the
1785                     short  name  is  not  all  upper  case.  This mode is the
1786                     default since Linux 2.6.32.
1787
1788
1789   Mount options for usbfs
1790       devuid=uid and devgid=gid and devmode=mode
1791              Set the owner and group and mode of  the  device  files  in  the
1792              usbfs  filesystem  (default: uid=gid=0, mode=0644).  The mode is
1793              given in octal.
1794
1795       busuid=uid and busgid=gid and busmode=mode
1796              Set the owner and group and mode of the bus directories  in  the
1797              usbfs  filesystem  (default: uid=gid=0, mode=0555).  The mode is
1798              given in octal.
1799
1800       listuid=uid and listgid=gid and listmode=mode
1801              Set the owner and group and mode of the file  devices  (default:
1802              uid=gid=0, mode=0444).  The mode is given in octal.
1803
1804

THE LOOP DEVICE

1806       One further possible type is a mount via the loop device.  For example,
1807       the command
1808
1809              mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1810
1811       will set up the loop  device  /dev/loop3  to  correspond  to  the  file
1812       /tmp/disk.img, and then mount this device on /mnt.
1813
1814       If  no  explicit loop device is mentioned (but just an option `-o loop'
1815       is given), then mount will try to find some unused loop device and  use
1816       that, for example
1817
1818              mount /tmp/disk.img /mnt -o loop
1819
1820       The  mount  command  automatically creates a loop device from a regular
1821       file if a filesystem type is not specified or the filesystem  is  known
1822       for libblkid, for example:
1823
1824              mount /tmp/disk.img /mnt
1825
1826              mount -t ext4 /tmp/disk.img /mnt
1827
1828       This  type  of mount knows about three options, namely loop, offset and
1829       sizelimit, that are really options to losetup(8).  (These  options  can
1830       be used in addition to those specific to the filesystem type.)
1831
1832       Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1833       ing that any loop device allocated by mount will  be  freed  by  umount
1834       independently of /etc/mtab.
1835
1836       You can also free a loop device by hand, using losetup -d or umount -d.
1837
1838       Since  util-linux  v2.29  mount  command re-uses the loop device rather
1839       than initialize a new device if the same backing file is  already  used
1840       for some loop device with the same offset and sizelimit. This is neces‐
1841       sary to avoid a filesystem corruption.
1842
1843

RETURN CODES

1845       mount has the following return codes (the bits can be ORed):
1846
1847       0      success
1848
1849       1      incorrect invocation or permissions
1850
1851       2      system error (out of memory, cannot fork, no more loop devices)
1852
1853       4      internal mount bug
1854
1855       8      user interrupt
1856
1857       16     problems writing or locking /etc/mtab
1858
1859       32     mount failure
1860
1861       64     some mount succeeded
1862
1863       The command mount -a returns 0 (all succeeded), 32 (all failed), or  64
1864       (some failed, some succeeded).
1865
1866

EXTERNAL HELPERS

1868       The syntax of external mount helpers is:
1869
1870           /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
1871           type.subtype]
1872
1873       where the suffix is the filesystem type and the  -sfnvoN  options  have
1874       the  same  meaning  as the normal mount options.  The -t option is used
1875       for filesystems with subtypes support (for example /sbin/mount.fuse  -t
1876       fuse.sshfs).
1877
1878       The  command mount does not pass the mount options unbindable, runbind‐
1879       able, private, rprivate, slave, rslave, shared, rshared, auto,  noauto,
1880       comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
1881       All other options are used in a comma-separated list as argument to the
1882       -o option.
1883
1884

FILES

1886       See  also  "The  files  /etc/fstab, /etc/mtab and /proc/mounts" section
1887       above.
1888
1889       /etc/fstab        filesystem table
1890
1891       /run/mount        libmount private runtime directory
1892
1893       /etc/mtab         table  of   mounted   filesystems   or   symlink   to
1894                         /proc/mounts
1895
1896       /etc/mtab~        lock file (unused on systems with mtab symlink)
1897
1898       /etc/mtab.tmp     temporary file (unused on systems with mtab symlink)
1899
1900       /etc/filesystems  a list of filesystem types to try
1901

ENVIRONMENT

1903       LIBMOUNT_FSTAB=<path>
1904              overrides  the  default  location of the fstab file (ignored for
1905              suid)
1906
1907       LIBMOUNT_MTAB=<path>
1908              overrides the default location of the  mtab  file  (ignored  for
1909              suid)
1910
1911       LIBMOUNT_DEBUG=all
1912              enables libmount debug output
1913
1914       LIBBLKID_DEBUG=all
1915              enables libblkid debug output
1916
1917       LOOPDEV_DEBUG=all
1918              enables loop device setup debug output
1919

SEE ALSO

1921       mount(2), umount(2), umount(8), fstab(5), nfs(5), xfs(5), e2label(8),
1922       findmnt(8), losetup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8),
1923       tune2fs(8), xfs_admin(8)
1924

BUGS

1926       It is possible for a corrupted filesystem to cause a crash.
1927
1928       Some  Linux filesystems don't support -o sync nor -o dirsync (the ext2,
1929       ext3, ext4, fat and vfat filesystems do support synchronous updates  (a
1930       la BSD) when mounted with the sync option).
1931
1932       The  -o remount may not be able to change mount parameters (all ext2fs-
1933       specific parameters, except sb, are  changeable  with  a  remount,  for
1934       example, but you can't change gid or umask for the fatfs).
1935
1936       It is possible that the files /etc/mtab and /proc/mounts don't match on
1937       systems with a regular mtab file.  The first file is based only on  the
1938       mount  command options, but the content of the second file also depends
1939       on the kernel and others settings (e.g. on a remote NFS  server  --  in
1940       certain cases the mount command may report unreliable information about
1941       an NFS mount point and the  /proc/mounts  file  usually  contains  more
1942       reliable information.)  This is another reason to replace the mtab file
1943       with a symlink to the /proc/mounts file.
1944
1945       Checking files on NFS filesystems referenced by file descriptors  (i.e.
1946       the  fcntl  and  ioctl  families of functions) may lead to inconsistent
1947       results due to the lack of a consistency check in the  kernel  even  if
1948       noac is used.
1949
1950       The loop option with the offset or sizelimit options used may fail when
1951       using older kernels if the mount command can't confirm that the size of
1952       the  block device has been configured as requested.  This situation can
1953       be worked around by using the losetup command manually  before  calling
1954       mount with the configured loop device.
1955

HISTORY

1957       A mount command existed in Version 5 AT&T UNIX.
1958

AUTHORS

1960       Karel Zak <kzak@redhat.com>
1961

AVAILABILITY

1963       The  mount  command  is part of the util-linux package and is available
1964       from https://www.kernel.org/pub/linux/utils/util-linux/.
1965
1966
1967
1968util-linux                        August 2015                         MOUNT(8)
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