1MOUNT(8)                     System Administration                    MOUNT(8)
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4

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 may 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 the ker‐
55       nel  and it is usually specific to the filesystem driver. The exception
56       is --all, in this case already mounted  filesystems  are  ignored  (see
57       --all 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 names of disk partitions are unstable; hardware reconfigura‐
84       tion, adding or removing a device can cause changes in names.  This  is
85       the reason why it's strongly recommended to use filesystem or partition
86       identifiers like UUID or LABEL.
87
88       The command lsblk --fs provides an 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       Since  version  2.35  mount command does not exit when user permissions
187       are inadequate by internal libmount security rules.  It drops suid per‐
188       missions  and  continue  as regular non-root user. It allows to support
189       use-cases where root permissions are not necessary (e.g., fuse filesys‐
190       tems, user namespaces, etc).
191
192       For  more details, see fstab(5).  Only the user that mounted a filesys‐
193       tem can unmount it again.  If any user should be able  to  unmount  it,
194       then  use users instead of user in the fstab line.  The owner option is
195       similar to the user option, with the restriction that the user must  be
196       the  owner of the special file.  This may be useful e.g. for /dev/fd if
197       a login script makes the console user owner of this device.  The  group
198       option is similar, with the restriction that the user must be member of
199       the group of the special file.
200
201
202   Bind mount operation
203       Remount part of the file hierarchy somewhere else.  The call is:
204
205              mount --bind olddir newdir
206
207       or by using this fstab entry:
208
209              /olddir /newdir none bind
210
211       After this call the same contents are accessible in two places.
212
213       It is important to understand that "bind" does not to create  any  sec‐
214       ond-class or special node in the kernel VFS. The "bind" is just another
215       operation to attach a filesystem. There is nowhere  stored  information
216       that  the  filesystem has been attached by "bind" operation. The olddir
217       and newdir are independent and the olddir may be umounted.
218
219       One can also remount a single file (on a single file).  It's also  pos‐
220       sible  to  use  the  bind  mount  to create a mountpoint from a regular
221       directory, for example:
222
223              mount --bind foo foo
224
225       The bind mount call attaches only (part of) a  single  filesystem,  not
226       possible  submounts.   The entire file hierarchy including submounts is
227       attached a second place by using:
228
229              mount --rbind olddir newdir
230
231       Note that the filesystem mount options maintained by kernel will remain
232       the  same  as  those  on the original mount point.  The userspace mount
233       options (e.g., _netdev) will not be copied by mount(8) and it's  neces‐
234       sary explicitly specify the options on mount command line.
235
236       mount(8)  since v2.27 allows to change the mount options by passing the
237       relevant options along with --bind.  For example:
238
239              mount -o bind,ro foo foo
240
241       This feature is not supported by the Linux kernel; it is implemented in
242       userspace by an additional mount(2) remounting system call.  This solu‐
243       tion is not atomic.
244
245       The alternative (classic) way to create a read-only bind  mount  is  to
246       use the remount operation, for example:
247
248              mount --bind olddir newdir
249              mount -o remount,bind,ro olddir newdir
250
251       Note  that  a  read-only  bind  will create a read-only mountpoint (VFS
252       entry), but the original filesystem superblock will still be  writable,
253       meaning  that the olddir will be writable, but the newdir will be read-
254       only.
255
256       It's also possible to change nosuid, nodev, noexec, noatime, nodiratime
257       and  relatime VFS entry flags by "remount,bind" operation.  The another
258       (for example filesystem specific flags)  are  silently  ignored.   It's
259       impossible  to  change  mount  options recursively (for example with -o
260       rbind,ro).
261
262       mount(8) since v2.31 ignores the bind flag from /etc/fstab  on  remount
263       operation  (if  "-o remount" specified on command line). This is neces‐
264       sary to fully control mount options on remount by command line. In  the
265       previous  versions  the  bind  flag  has been always applied and it was
266       impossible to re-define mount options without interaction with the bind
267       semantic.  This  mount(8)  behavior  does  not  affect  situations when
268       "remount,bind" is specified in the /etc/fstab file.
269
270
271   The move operation
272       Move a mounted tree to another place (atomically).  The call is:
273
274              mount --move olddir newdir
275
276       This will cause the contents which previously appeared under olddir  to
277       now  be accessible under newdir.  The physical location of the files is
278       not changed.  Note that olddir has to be a mountpoint.
279
280       Note also that moving a mount residing under a shared mount is  invalid
281       and  unsupported.  Use findmnt -o TARGET,PROPAGATION to see the current
282       propagation flags.
283
284
285   Shared subtree operations
286       Since Linux 2.6.15 it is possible to mark a mount and its submounts  as
287       shared,  private,  slave  or  unbindable.   A shared mount provides the
288       ability to create mirrors of that mount such that mounts  and  unmounts
289       within any of the mirrors propagate to the other mirror.  A slave mount
290       receives propagation from its master, but not vice  versa.   A  private
291       mount  carries no propagation abilities.  An unbindable mount is a pri‐
292       vate mount which cannot  be  cloned  through  a  bind  operation.   The
293       detailed  semantics are documented in Documentation/filesystems/shared‐
294       subtree.txt file in the kernel source tree.
295
296       Supported operations are:
297
298              mount --make-shared mountpoint
299              mount --make-slave mountpoint
300              mount --make-private mountpoint
301              mount --make-unbindable mountpoint
302
303       The following commands allow one to recursively change the type of  all
304       the mounts under a given mountpoint.
305
306              mount --make-rshared mountpoint
307              mount --make-rslave mountpoint
308              mount --make-rprivate mountpoint
309              mount --make-runbindable mountpoint
310
311       mount(8) does not read fstab(5) when a --make-* operation is requested.
312       All necessary information has to be specified on the command line.
313
314       Note that the Linux kernel does not allow to change  multiple  propaga‐
315       tion  flags with a single mount(2) system call, and the flags cannot be
316       mixed with other mount options and operations.
317
318       Since util-linux 2.23 the mount command allows to do  more  propagation
319       (topology)  changes  by  one mount(8) call and do it also together with
320       other mount operations.  This feature is EXPERIMENTAL.  The propagation
321       flags  are applied by additional mount(2) system calls when the preced‐
322       ing mount operations were successful.  Note that this use case  is  not
323       atomic.  It is possible to specify the propagation flags in fstab(5) as
324       mount options (private, slave, shared,  unbindable,  rprivate,  rslave,
325       rshared, runbindable).
326
327       For example:
328
329              mount --make-private --make-unbindable /dev/sda1 /foo
330
331       is the same as:
332
333              mount /dev/sda1 /foox
334              mount --make-private /foo
335              mount --make-unbindable /foo
336
337

COMMAND-LINE OPTIONS

339       The  full set of mount options used by an invocation of mount is deter‐
340       mined by first extracting the mount options for the filesystem from the
341       fstab  table,  then  applying any options specified by the -o argument,
342       and finally applying a -r or -w option, when present.
343
344       The command mount  does  not  pass  all  command-line  options  to  the
345       /sbin/mount.suffix  mount helpers.  The interface between mount and the
346       mount helpers is described below in the section EXTERNAL HELPERS.
347
348       Command-line options available for the mount command are:
349
350       -a, --all
351              Mount all filesystems (of the given types)  mentioned  in  fstab
352              (except  for those whose line contains the noauto keyword).  The
353              filesystems are mounted following their  order  in  fstab.   The
354              mount  command  compares  filesystem source, target (and fs root
355              for bind mount or btrfs) to detect already mounted  filesystems.
356              The kernel table with already mounted filesystems is cached dur‐
357              ing mount --all. It means that all duplicated fstab entries will
358              be mounted.
359
360              The  option  --all is possible to use for remount operation too.
361              In this case all filters (-t and -O) are applied to the table of
362              already mounted filesystems.
363
364              Since version 2.35 is possible to use the command line option -o
365              to alter mount options from fstab (see also --options-mode).
366
367              Note that it is a bad practice to use mount -a for fstab  check‐
368              ing. The recommended solution is findmnt --verify.
369
370       -B, --bind
371              Remount  a  subtree  somewhere  else  (so  that its contents are
372              available in both places).  See above, under Bind mounts.
373
374       -c, --no-canonicalize
375              Don't canonicalize paths.  The mount command  canonicalizes  all
376              paths  (from command line or fstab) by default.  This option can
377              be used together with the  -f  flag  for  already  canonicalized
378              absolute  paths.  The option is designed for mount helpers which
379              call mount -i.  It is strongly recommended to not use this  com‐
380              mand-line option for normal mount operations.
381
382              Note   that   mount(8)   does   not  pass  this  option  to  the
383              /sbin/mount.type helpers.
384
385       -F, --fork
386              (Used in conjunction with -a.)  Fork off a  new  incarnation  of
387              mount  for  each  device.   This will do the mounts on different
388              devices or different NFS servers  in  parallel.   This  has  the
389              advantage  that  it is faster; also NFS timeouts go in parallel.
390              A disadvantage is that the mounts are done in  undefined  order.
391              Thus,  you cannot use this option if you want to mount both /usr
392              and /usr/spool.
393
394       -f, --fake
395              Causes everything to be done except for the actual system  call;
396              if  it's  not  obvious,  this ``fakes'' mounting the filesystem.
397              This option is useful in conjunction with the -v flag to  deter‐
398              mine  what  the  mount  command is trying to do.  It can also be
399              used to add entries for devices that were mounted  earlier  with
400              the  -n  option.  The -f option checks for an existing record in
401              /etc/mtab and fails when the record already exists (with a regu‐
402              lar non-fake mount, this check is done by the kernel).
403
404       -i, --internal-only
405              Don't call the /sbin/mount.filesystem helper even if it exists.
406
407       -L, --label label
408              Mount the partition that has the specified label.
409
410       -l, --show-labels
411              Add  the labels in the mount output.  mount must have permission
412              to read the disk device (e.g. be set-user-ID root) for  this  to
413              work.  One can set such a label for ext2, ext3 or ext4 using the
414              e2label(8) utility, or for XFS using xfs_admin(8), or for  reis‐
415              erfs using reiserfstune(8).
416
417       -M, --move
418              Move  a  subtree to some other place.  See above, the subsection
419              The move operation.
420
421       -n, --no-mtab
422              Mount without writing in /etc/mtab.  This is necessary for exam‐
423              ple when /etc is on a read-only filesystem.
424
425       -N, --namespace ns
426              Perform mount in namespace specified by ns.  ns is either PID of
427              process running in that namespace or special  file  representing
428              that namespace.
429
430              mount(8)  switches  to  the  namespace when it reads /etc/fstab,
431              writes /etc/mtab (or writes to /run/mount)  and  calls  mount(2)
432              system  call,  otherwise  it  runs in the original namespace. It
433              means that the target namespace does not  have  to  contain  any
434              libraries  or another requirements necessary to execute mount(2)
435              command.
436
437              See namespaces(7) for more information.
438
439       -O, --test-opts opts
440              Limit the set of filesystems to which the -a option applies.  In
441              this  regard  it is like the -t option except that -O is useless
442              without -a.  For example, the command:
443
444                     mount -a -O no_netdev
445
446              mounts all filesystems except those which have the option  _net‐
447              dev specified in the options field in the /etc/fstab file.
448
449              It  is different from -t in that each option is matched exactly;
450              a leading no at the beginning of one option does not negate  the
451              rest.
452
453              The  -t  and  -O  options are cumulative in effect; that is, the
454              command
455
456                     mount -a -t ext2 -O _netdev
457
458              mounts all ext2 filesystems with the  _netdev  option,  not  all
459              filesystems  that  are  either  ext2  or have the _netdev option
460              specified.
461
462       -o, --options opts
463              Use the specified mount options.  The opts argument is a  comma-
464              separated list.  For example:
465
466                     mount LABEL=mydisk -o noatime,nodev,nosuid
467
468
469              For  more  details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS
470              and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
471
472
473       --options-mode mode
474              Controls how to combine options  from  fstab/mtab  with  options
475              from  command  line.  mode can be one of ignore, append, prepend
476              or replace.  For example append means that  options  from  fstab
477              are  appended  to  options  from command line.  Default value is
478              prepend -- it means command line  options  are  evaluated  after
479              fstab options.  Note that the last option wins if there are con‐
480              flicting ones.
481
482
483       --options-source source
484              Source of default options.  source is comma  separated  list  of
485              fstab,  mtab  and  disable.  disable disables fstab and mtab and
486              disables --options-source-force.  Default value is fstab,mtab.
487
488
489       --options-source-force
490              Use options from fstab/mtab even if  both  device  and  dir  are
491              specified.
492
493
494       -R, --rbind
495              Remount  a subtree and all possible submounts somewhere else (so
496              that its contents are available in both places).  See above, the
497              subsection Bind mounts.
498
499       -r, --read-only
500              Mount the filesystem read-only.  A synonym is -o ro.
501
502              Note  that,  depending  on the filesystem type, state and kernel
503              behavior, the system may still write to the device.   For  exam‐
504              ple,  ext3 and ext4 will replay the journal if the filesystem is
505              dirty.  To prevent this kind of write access, you  may  want  to
506              mount  an  ext3  or  ext4  filesystem  with  the ro,noload mount
507              options or set the block device itself to  read-only  mode,  see
508              the blockdev(8) command.
509
510       -s     Tolerate  sloppy  mount  options rather than failing.  This will
511              ignore mount options not supported by a  filesystem  type.   Not
512              all  filesystems  support this option.  Currently it's supported
513              by the mount.nfs mount helper only.
514
515       --source device
516              If only one argument for the mount command  is  given  then  the
517              argument  might  be interpreted as target (mountpoint) or source
518              (device).  This option allows  to  explicitly  define  that  the
519              argument is the mount source.
520
521       --target directory
522              If  only  one  argument  for the mount command is given then the
523              argument might be interpreted as target (mountpoint)  or  source
524              (device).   This  option  allows  to  explicitly define that the
525              argument is the mount target.
526
527       --target-prefix directory
528              Prepend specified directory to all mount targets.   This  option
529              allows  to follow fstab, but mount operations is done on another
530              place, for example:
531
532                     mount --all --target-prefix /chroot -o X-mount.mkdir
533
534              mounts all from system fstab to /chroot, all missing  muontpoint
535              are  created (due to X-mount.mkdir).  See also --fstab to use an
536              alternative fstab.
537
538       -T, --fstab path
539              Specifies an alternative fstab file.  If  path  is  a  directory
540              then  the  files  in  the directory are sorted by strverscmp(3);
541              files that start with "." or without  an  .fstab  extension  are
542              ignored.   The  option  can  be  specified more than once.  This
543              option is mostly designed for initramfs or chroot scripts  where
544              additional  configuration  is  specified  beyond standard system
545              configuration.
546
547              Note that mount(8) does not  pass  the  option  --fstab  to  the
548              /sbin/mount.type  helpers,  meaning  that  the alternative fstab
549              files will be invisible for the helpers.  This is no problem for
550              normal  mounts,  but user (non-root) mounts always require fstab
551              to verify the user's rights.
552
553       -t, --types fstype
554              The argument following the -t is used to indicate the filesystem
555              type.  The filesystem types which are currently supported depend
556              on the running  kernel.   See  /proc/filesystems  and  /lib/mod‐
557              ules/$(uname  -r)/kernel/fs  for a complete list of the filesys‐
558              tems.  The most common are ext2, ext3, ext4, xfs,  btrfs,  vfat,
559              sysfs, proc, nfs and cifs.
560
561              The  programs mount and umount support filesystem subtypes.  The
562              subtype  is  defined  by  a  '.subtype'  suffix.   For   example
563              'fuse.sshfs'.   It's  recommended to use subtype notation rather
564              than  add  any  prefix  to  the  mount   source   (for   example
565              'sshfs#example.com' is deprecated).
566
567              If  no  -t  option  is  given, or if the auto type is specified,
568              mount will try to guess the desired type.  Mount uses the  blkid
569              library  for guessing the filesystem type; if that does not turn
570              up anything that looks familiar, mount will try to read the file
571              /etc/filesystems, or, if that does not exist, /proc/filesystems.
572              All of the filesystem types listed there will be  tried,  except
573              for  those that are labeled "nodev" (e.g. devpts, proc and nfs).
574              If /etc/filesystems ends in a line with a single *,  mount  will
575              read /proc/filesystems afterwards.  While trying, all filesystem
576              types will be mounted with the mount option silent.
577
578              The auto type may be useful for user-mounted floppies.  Creating
579              a  file /etc/filesystems can be useful to change the probe order
580              (e.g., to try vfat before msdos or ext3 before ext2) or  if  you
581              use a kernel module autoloader.
582
583              More  than  one type may be specified in a comma-separated list,
584              for option -t as well as in an /etc/fstab entry.   The  list  of
585              filesystem  types for option -t can be prefixed with no to spec‐
586              ify the filesystem types on which no  action  should  be  taken.
587              The  prefix  no  has  no  effect when specified in an /etc/fstab
588              entry.
589
590              The prefix no can be meaningful with the -a option.   For  exam‐
591              ple, the command
592
593                     mount -a -t nomsdos,smbfs
594
595              mounts all filesystems except those of type msdos and smbfs.
596
597              For most types all the mount program has to do is issue a simple
598              mount(2) system call, and no detailed knowledge of the  filesys‐
599              tem  type is required.  For a few types however (like nfs, nfs4,
600              cifs, smbfs, ncpfs) an ad hoc code is necessary.  The nfs, nfs4,
601              cifs,  smbfs,  and  ncpfs filesystems have a separate mount pro‐
602              gram.  In order to make it possible to treat all types in a uni‐
603              form  way,  mount  will execute the program /sbin/mount.type (if
604              that exists) when called with type type.  Since  different  ver‐
605              sions  of  the  smbmount  program have different calling conven‐
606              tions, /sbin/mount.smbfs may have to be a shell script that sets
607              up the desired call.
608
609       -U, --uuid uuid
610              Mount the partition that has the specified uuid.
611
612       -v, --verbose
613              Verbose mode.
614
615       -w, --rw, --read-write
616              Mount  the  filesystem  read/write.  The  read-write  is  kernel
617              default.  A synonym is -o rw.
618
619              Note that specify -w on command line  forces  mount  command  to
620              never  try  read-only  mount  on  write-protected  devices.  The
621              default is try read-only if  the  previous  mount  syscall  with
622              read-write flags failed.
623
624       -V, --version
625              Display version information and exit.
626
627       -h, --help
628              Display help text and exit.
629
630

FILESYSTEM-INDEPENDENT MOUNT OPTIONS

632       Some  of  these  options  are  only  useful  when  they  appear  in the
633       /etc/fstab file.
634
635       Some of these options could be enabled or disabled by  default  in  the
636       system  kernel.   To  check  the  current  setting  see  the options in
637       /proc/mounts.  Note that filesystems also have per-filesystem  specific
638       default  mount  options  (see  for  example  tune2fs -l output for extN
639       filesystems).
640
641       The following options apply to any filesystem  that  is  being  mounted
642       (but  not every filesystem actually honors them – e.g., the sync option
643       today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
644
645
646       async  All I/O to the filesystem should be done  asynchronously.   (See
647              also the sync option.)
648
649       atime  Do not use the noatime feature, so the inode access time is con‐
650              trolled by kernel defaults.  See also the  descriptions  of  the
651              relatime and strictatime mount options.
652
653       noatime
654              Do  not  update  inode access times on this filesystem (e.g. for
655              faster access on the news spool to speed up news servers).  This
656              works  for  all  inode  types  (directories  too), so it implies
657              nodiratime.
658
659       auto   Can be mounted with the -a option.
660
661       noauto Can only be mounted explicitly (i.e., the  -a  option  will  not
662              cause the filesystem to be mounted).
663
664       context=context, fscontext=context, defcontext=context, and
665       rootcontext=context
666              The context= option is useful when mounting filesystems that  do
667              not  support  extended attributes, such as a floppy or hard disk
668              formatted with VFAT, or systems that are  not  normally  running
669              under SELinux, such as an ext3 or ext4 formatted
670
671              disk  from a non-SELinux workstation.  You can also use context=
672              on filesystems you do not trust, such  as  a  floppy.   It  also
673              helps in compatibility with xattr-supporting filesystems on ear‐
674              lier 2.4.<x> kernel versions.  Even where xattrs are  supported,
675              you  can  save  time not having to label every file by assigning
676              the entire disk one security context.
677
678              A   commonly   used    option    for    removable    media    is
679              context="system_u:object_r:removable_t".
680
681              Two  other options are fscontext= and defcontext=, both of which
682              are mutually exclusive of the context option.   This  means  you
683              can  use  fscontext  and defcontext with each other, but neither
684              can be used with context.
685
686              The fscontext= option works for all filesystems,  regardless  of
687              their  xattr support.  The fscontext option sets the overarching
688              filesystem label to a specific security context.  This  filesys‐
689              tem  label  is separate from the individual labels on the files.
690              It represents the entire filesystem for certain kinds of permis‐
691              sion  checks, such as during mount or file creation.  Individual
692              file labels are still obtained from  the  xattrs  on  the  files
693              themselves.  The context option actually sets the aggregate con‐
694              text that fscontext provides, in addition to supplying the  same
695              label for individual files.
696
697              You  can  set  the  default security context for unlabeled files
698              using defcontext= option.  This  overrides  the  value  set  for
699              unlabeled  files  in  the  policy and requires a filesystem that
700              supports xattr labeling.
701
702              The rootcontext= option allows you to explicitly label the  root
703              inode of a FS being mounted before that FS or inode becomes vis‐
704              ible to userspace.  This was found to be useful for things  like
705              stateless linux.
706
707              Note  that  the kernel rejects any remount request that includes
708              the context option, even when unchanged from  the  current  con‐
709              text.
710
711              Warning:  the  context value might contain commas, in which case
712              the value has to be properly  quoted,  otherwise  mount(8)  will
713              interpret the comma as a separator between mount options.  Don't
714              forget that the shell strips off quotes and thus double  quoting
715              is required.  For example:
716
717                     mount -t tmpfs none /mnt -o \
718                       'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
719
720              For more details, see selinux(8).
721
722
723       defaults
724              Use  the default options: rw, suid, dev, exec, auto, nouser, and
725              async.
726
727              Note that the real set of all default mount options  depends  on
728              kernel  and  filesystem type.  See the beginning of this section
729              for more details.
730
731       dev    Interpret character or block special devices on the filesystem.
732
733       nodev  Do not interpret character or block special devices on the  file
734              system.
735
736       diratime
737              Update directory inode access times on this filesystem.  This is
738              the default.  (This option is ignored when noatime is set.)
739
740       nodiratime
741              Do not update directory inode access times on  this  filesystem.
742              (This option is implied when noatime is set.)
743
744       dirsync
745              All  directory updates within the filesystem should be done syn‐
746              chronously.  This affects the  following  system  calls:  creat,
747              link, unlink, symlink, mkdir, rmdir, mknod and rename.
748
749       exec   Permit execution of binaries.
750
751       noexec Do  not  permit  direct execution of any binaries on the mounted
752              filesystem.
753
754       group  Allow an ordinary user to mount the filesystem if  one  of  that
755              user's  groups  matches  the  group  of the device.  This option
756              implies the options nosuid and nodev (unless overridden by  sub‐
757              sequent options, as in the option line group,dev,suid).
758
759       iversion
760              Every  time  the  inode is modified, the i_version field will be
761              incremented.
762
763       noiversion
764              Do not increment the i_version inode field.
765
766       mand   Allow mandatory locks on this filesystem.  See fcntl(2).
767
768       nomand Do not allow mandatory locks on this filesystem.
769
770       _netdev
771              The filesystem resides on a device that requires network  access
772              (used  to  prevent  the  system  from  attempting to mount these
773              filesystems until the network has been enabled on the system).
774
775       nofail Do not report errors for this device if it does not exist.
776
777       relatime
778              Update inode access times relative to  modify  or  change  time.
779              Access time is only updated if the previous access time was ear‐
780              lier than the  current  modify  or  change  time.   (Similar  to
781              noatime,  but  it  doesn't break mutt or other applications that
782              need to know if a file has been read since the last time it  was
783              modified.)
784
785              Since Linux 2.6.30, the kernel defaults to the behavior provided
786              by  this  option  (unless  noatime  was  specified),   and   the
787              strictatime  option is required to obtain traditional semantics.
788              In addition, since Linux 2.6.30, the file's last access time  is
789              always updated if it is more than 1 day old.
790
791       norelatime
792              Do not use the relatime feature.  See also the strictatime mount
793              option.
794
795       strictatime
796              Allows to explicitly request full atime updates.  This makes  it
797              possible  for  the  kernel to default to relatime or noatime but
798              still allow userspace to override it.  For  more  details  about
799              the default system mount options see /proc/mounts.
800
801       nostrictatime
802              Use the kernel's default behavior for inode access time updates.
803
804       lazytime
805              Only update times (atime, mtime, ctime) on the in-memory version
806              of the file inode.
807
808              This mount option significantly reduces writes to the inode  ta‐
809              ble  for workloads that perform frequent random writes to preal‐
810              located files.
811
812              The on-disk timestamps are updated only when:
813
814              - the inode needs to be updated for  some  change  unrelated  to
815              file timestamps
816
817              - the application employs fsync(2), syncfs(2), or sync(2)
818
819              - an undeleted inode is evicted from memory
820
821              - more than 24 hours have passed since the i-node was written to
822              disk.
823
824
825       nolazytime
826              Do not use the lazytime feature.
827
828       suid   Honor set-user-ID and set-group-ID  bits  or  file  capabilities
829              when executing programs from this filesystem.
830
831       nosuid Do not honor set-user-ID and set-group-ID bits or file capabili‐
832              ties when executing programs from this filesystem.
833
834       silent Turn on the silent flag.
835
836       loud   Turn off the silent flag.
837
838       owner  Allow an ordinary user to mount the filesystem if that  user  is
839              the owner of the device.  This option implies the options nosuid
840              and nodev (unless overridden by subsequent options,  as  in  the
841              option line owner,dev,suid).
842
843       remount
844              Attempt  to remount an already-mounted filesystem.  This is com‐
845              monly used to change the mount flags  for  a  filesystem,  espe‐
846              cially  to  make  a  readonly  filesystem writable.  It does not
847              change device or mount point.
848
849              The remount operation together with the bind  flag  has  special
850              semantic. See above, the subsection Bind mounts.
851
852              The  remount  functionality  follows  the standard way the mount
853              command works with options from fstab.  This  means  that  mount
854              does  not read fstab (or mtab) only when both device and dir are
855              specified.
856
857                  mount -o remount,rw /dev/foo /dir
858
859              After this call all old mount options are replaced and arbitrary
860              stuff  from  fstab (or mtab) is ignored, except the loop= option
861              which is internally generated and maintained by the  mount  com‐
862              mand.
863
864                  mount -o remount,rw  /dir
865
866              After this call, mount reads fstab and merges these options with
867              the options from the command line (-o).   If  no  mountpoint  is
868              found  in  fstab,  then  a  remount  with  unspecified source is
869              allowed.
870
871              mount(8) allows to use --all  to  remount  all  already  mounted
872              filesystems  which  match  a  specified filter (-O and -t).  For
873              example:
874
875                  mount --all -o remount,ro -t vfat
876
877              remounts all already mounted vfat filesystems in read-only mode.
878              The each of the filesystems is remounted by "mount -o remount,ro
879              /dir" semantic. It means the mount command reads fstab  or  mtab
880              and merges these options with the options from the command line.
881
882       ro     Mount the filesystem read-only.
883
884       rw     Mount the filesystem read-write.
885
886       sync   All  I/O to the filesystem should be done synchronously.  In the
887              case of media with a limited number of write cycles  (e.g.  some
888              flash drives), sync may cause life-cycle shortening.
889
890       user   Allow an ordinary user to mount the filesystem.  The name of the
891              mounting user is written to the mtab file  (or  to  the  private
892              libmount  file  in /run/mount on systems without a regular mtab)
893              so that this same user can unmount the filesystem  again.   This
894              option  implies  the  options  noexec, nosuid, and nodev (unless
895              overridden  by  subsequent  options,  as  in  the  option   line
896              user,exec,dev,suid).
897
898       nouser Forbid  an  ordinary  user to mount the filesystem.  This is the
899              default; it does not imply any other options.
900
901       users  Allow any user to mount and to unmount the filesystem, even when
902              some  other  ordinary  user mounted it.  This option implies the
903              options noexec, nosuid, and nodev (unless overridden  by  subse‐
904              quent options, as in the option line users,exec,dev,suid).
905
906       X-*    All options prefixed with "X-" are interpreted as comments or as
907              userspace application-specific options.  These options  are  not
908              stored  in  the  user  space  (e.g., mtab file), nor sent to the
909              mount.type helpers nor to the mount(2) system  call.   The  sug‐
910              gested format is X-appname.option.
911
912       x-*    The  same  as  X-*  options,  but stored permanently in the user
913              space. It means the options are also  available  for  umount  or
914              another  operations.   Note  that maintain mount options in user
915              space is tricky, because it's necessary use libmount based tools
916              and there is no guarantee that the options will be always avail‐
917              able (for example after a move mount operation  or  in  unshared
918              namespace).
919
920              Note  that before util-linux v2.30 the x-* options have not been
921              maintained by libmount and stored in user  space  (functionality
922              was the same as have X-* now), but due to growing number of use-
923              cases (in initrd, systemd  etc.)  the  functionality  have  been
924              extended  to keep existing fstab configurations usable without a
925              change.
926
927       X-mount.mkdir[=mode]
928              Allow to make a target directory (mountpoint)  if  it  does  not
929              exit  yet.   The optional argument mode specifies the filesystem
930              access mode used for mkdir(2) in octal  notation.   The  default
931              mode  is  0755.   This  functionality is supported only for root
932              users or when mount  executed  without  suid  permissions.   The
933              option is also supported as x-mount.mkdir, this notation is dep‐
934              recated since v2.30.
935
936

FILESYSTEM-SPECIFIC MOUNT OPTIONS

938       You should consult the respective man page for  the  filesystem  first.
939       If  you  want  to  know what options the ext4 filesystem supports, then
940       check the ext4(5) man page.  If that doesn't exist, you can also  check
941       the  corresponding  mount page like mount.cifs(8).  Note that you might
942       have to install the respective userland tools.
943
944       The following options apply only to certain filesystems.  We sort  them
945       by filesystem.  They all follow the -o flag.
946
947       What  options  are supported depends a bit on the running kernel.  More
948       info  may  be  found  in  the  kernel  source  subdirectory  Documenta‐
949       tion/filesystems.
950
951
952   Mount options for adfs
953       uid=value and gid=value
954              Set the owner and group of the files in the filesystem (default:
955              uid=gid=0).
956
957       ownmask=value and othmask=value
958              Set the permission mask for ADFS 'owner' permissions and 'other'
959              permissions,  respectively  (default:  0700  and  0077,  respec‐
960              tively).    See    also    /usr/src/linux/Documentation/filesys‐
961              tems/adfs.txt.
962
963
964   Mount options for affs
965       uid=value and gid=value
966              Set  the owner and group of the root of the filesystem (default:
967              uid=gid=0, but with option uid or gid without  specified  value,
968              the UID and GID of the current process are taken).
969
970       setuid=value and setgid=value
971              Set the owner and group of all files.
972
973       mode=value
974              Set the mode of all files to value & 0777 disregarding the orig‐
975              inal permissions.  Add search  permission  to  directories  that
976              have read permission.  The value is given in octal.
977
978       protect
979              Do  not allow any changes to the protection bits on the filesys‐
980              tem.
981
982       usemp  Set UID and GID of the root of the filesystem to the UID and GID
983              of the mount point upon the first sync or umount, and then clear
984              this option.  Strange...
985
986       verbose
987              Print an informational message for each successful mount.
988
989       prefix=string
990              Prefix used before volume name, when following a link.
991
992       volume=string
993              Prefix (of length at most 30) used before '/' when  following  a
994              symbolic link.
995
996       reserved=value
997              (Default:  2.)  Number  of  unused  blocks  at  the start of the
998              device.
999
1000       root=value
1001              Give explicitly the location of the root block.
1002
1003       bs=value
1004              Give blocksize.  Allowed values are 512, 1024, 2048, 4096.
1005
1006       grpquota|noquota|quota|usrquota
1007              These options are accepted but ignored.  (However, quota  utili‐
1008              ties may react to such strings in /etc/fstab.)
1009
1010
1011   Mount options for debugfs
1012       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1013       /sys/kernel/debug.  As of kernel version 3.4, debugfs has the following
1014       options:
1015
1016       uid=n, gid=n
1017              Set the owner and group of the mountpoint.
1018
1019       mode=value
1020              Sets the mode of the mountpoint.
1021
1022
1023   Mount options for devpts
1024       The  devpts filesystem is a pseudo filesystem, traditionally mounted on
1025       /dev/pts.  In order to acquire  a  pseudo  terminal,  a  process  opens
1026       /dev/ptmx;  the number of the pseudo terminal is then made available to
1027       the  process  and  the  pseudo  terminal  slave  can  be  accessed   as
1028       /dev/pts/<number>.
1029
1030       uid=value and gid=value
1031              This  sets  the  owner or the group of newly created PTYs to the
1032              specified values.  When nothing is specified, they will  be  set
1033              to  the  UID  and  GID of the creating process.  For example, if
1034              there is a tty group with GID 5, then  gid=5  will  cause  newly
1035              created PTYs to belong to the tty group.
1036
1037       mode=value
1038              Set  the mode of newly created PTYs to the specified value.  The
1039              default is 0600.  A value of mode=620 and gid=5 makes  "mesg  y"
1040              the default on newly created PTYs.
1041
1042       newinstance
1043              Create  a  private  instance  of  devpts  filesystem,  such that
1044              indices of ptys allocated in this new instance  are  independent
1045              of indices created in other instances of devpts.
1046
1047              All  mounts  of devpts without this newinstance option share the
1048              same set of pty indices (i.e.,  legacy  mode).   Each  mount  of
1049              devpts  with  the  newinstance  option  has a private set of pty
1050              indices.
1051
1052              This option is mainly used to support containers  in  the  linux
1053              kernel.   It  is  implemented  in linux kernel versions starting
1054              with 2.6.29.  Further, this mount option is valid only  if  CON‐
1055              FIG_DEVPTS_MULTIPLE_INSTANCES  is enabled in the kernel configu‐
1056              ration.
1057
1058              To use this option effectively, /dev/ptmx  must  be  a  symbolic
1059              link  to  pts/ptmx.  See Documentation/filesystems/devpts.txt in
1060              the linux kernel source tree for details.
1061
1062       ptmxmode=value
1063
1064              Set the mode for the new ptmx device node in the devpts filesys‐
1065              tem.
1066
1067              With  the  support  for multiple instances of devpts (see newin‐
1068              stance option above), each instance has a private ptmx  node  in
1069              the root of the devpts filesystem (typically /dev/pts/ptmx).
1070
1071              For compatibility with older versions of the kernel, the default
1072              mode of the new ptmx node is 0000.  ptmxmode=value  specifies  a
1073              more  useful  mode  for  the ptmx node and is highly recommended
1074              when the newinstance option is specified.
1075
1076              This option is only implemented in linux kernel versions  start‐
1077              ing  with  2.6.29.   Further,  this option is valid only if CON‐
1078              FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu‐
1079              ration.
1080
1081
1082   Mount options for fat
1083       (Note:  fat  is  not  a  separate  filesystem, but a common part of the
1084       msdos, umsdos and vfat filesystems.)
1085
1086       blocksize={512|1024|2048}
1087              Set blocksize (default 512).  This option is obsolete.
1088
1089       uid=value and gid=value
1090              Set the owner and group of all files.  (Default: the UID and GID
1091              of the current process.)
1092
1093       umask=value
1094              Set  the  umask  (the  bitmask  of  the permissions that are not
1095              present).  The default is the umask of the current process.  The
1096              value is given in octal.
1097
1098       dmask=value
1099              Set  the  umask applied to directories only.  The default is the
1100              umask of the current process.  The value is given in octal.
1101
1102       fmask=value
1103              Set the umask applied to regular files only.  The default is the
1104              umask of the current process.  The value is given in octal.
1105
1106       allow_utime=value
1107              This option controls the permission check of mtime/atime.
1108
1109              20     If  current  process  is in group of file's group ID, you
1110                     can change timestamp.
1111
1112              2      Other users can change timestamp.
1113
1114              The default is set from `dmask' option.  (If  the  directory  is
1115              writable, utime(2) is also allowed.  I.e. ~dmask & 022)
1116
1117              Normally  utime(2)  checks current process is owner of the file,
1118              or it has CAP_FOWNER capability.   But  FAT  filesystem  doesn't
1119              have  UID/GID  on disk, so normal check is too inflexible.  With
1120              this option you can relax it.
1121
1122       check=value
1123              Three different levels of pickiness can be chosen:
1124
1125              r[elaxed]
1126                     Upper and lower case are accepted  and  equivalent,  long
1127                     name   parts   are  truncated  (e.g.  verylongname.foobar
1128                     becomes verylong.foo), leading and  embedded  spaces  are
1129                     accepted in each name part (name and extension).
1130
1131              n[ormal]
1132                     Like  "relaxed",  but  many  special characters (*, ?, <,
1133                     spaces, etc.) are rejected.  This is the default.
1134
1135              s[trict]
1136                     Like "normal", but names that contain long parts or  spe‐
1137                     cial  characters that are sometimes used on Linux but are
1138                     not accepted by MS-DOS (+, =, etc.) are rejected.
1139
1140       codepage=value
1141              Sets the codepage for converting to shortname characters on  FAT
1142              and VFAT filesystems.  By default, codepage 437 is used.
1143
1144       conv=mode
1145              This option is obsolete and may fail or being ignored.
1146
1147       cvf_format=module
1148              Forces the driver to use the CVF (Compressed Volume File) module
1149              cvf_module instead of auto-detection.  If  the  kernel  supports
1150              kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1151              ule loading.  This option is obsolete.
1152
1153       cvf_option=option
1154              Option passed to the CVF module.  This option is obsolete.
1155
1156       debug  Turn on the debug flag.  A version string and a list of filesys‐
1157              tem  parameters  will be printed (these data are also printed if
1158              the parameters appear to be inconsistent).
1159
1160       discard
1161              If set, causes discard/TRIM commands to be issued to  the  block
1162              device  when  blocks  are freed.  This is useful for SSD devices
1163              and sparse/thinly-provisioned LUNs.
1164
1165       dos1xfloppy
1166              If set, use a fallback default BIOS Parameter  Block  configura‐
1167              tion,  determined  by backing device size.  These static parame‐
1168              ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1169              kiB, and 360 kiB floppies and floppy images.
1170
1171       errors={panic|continue|remount-ro}
1172              Specify FAT behavior on critical errors: panic, continue without
1173              doing anything, or  remount  the  partition  in  read-only  mode
1174              (default behavior).
1175
1176       fat={12|16|32}
1177              Specify  a  12,  16 or 32 bit fat.  This overrides the automatic
1178              FAT type detection routine.  Use with caution!
1179
1180       iocharset=value
1181              Character set to use for converting between 8 bit characters and
1182              16  bit  Unicode  characters.   The  default is iso8859-1.  Long
1183              filenames are stored on disk in Unicode format.
1184
1185       nfs={stale_rw|nostale_ro}
1186              Enable this only if you want to export the FAT  filesystem  over
1187              NFS.
1188
1189              stale_rw:  This  option  maintains an index (cache) of directory
1190              inodes which is used by the nfs-related code  to  improve  look-
1191              ups.   Full  file operations (read/write) over NFS are supported
1192              but with cache eviction at NFS server, this could result in spu‐
1193              rious ESTALE errors.
1194
1195              nostale_ro:  This  option bases the inode number and file handle
1196              on the on-disk location of a file in the  FAT  directory  entry.
1197              This  ensures  that  ESTALE will not be returned after a file is
1198              evicted from the inode cache.  However, it means that operations
1199              such  as rename, create and unlink could cause file handles that
1200              previously pointed at one file to point  at  a  different  file,
1201              potentially  causing  data  corruption.   For  this reason, this
1202              option also mounts the filesystem readonly.
1203
1204              To maintain backward compatibility, '-o nfs' is  also  accepted,
1205              defaulting to stale_rw.
1206
1207       tz=UTC This  option disables the conversion of timestamps between local
1208              time (as used by Windows on  FAT)  and  UTC  (which  Linux  uses
1209              internally).   This is particularly useful when mounting devices
1210              (like digital cameras) that are set to UTC in order to avoid the
1211              pitfalls of local time.
1212
1213       time_offset=minutes
1214              Set  offset for conversion of timestamps from local time used by
1215              FAT to UTC.  I.e., minutes will be subtracted  from  each  time‐
1216              stamp  to  convert  it to UTC used internally by Linux.  This is
1217              useful when the time zone set in the kernel via  settimeofday(2)
1218              is  not  the  time  zone used by the filesystem.  Note that this
1219              option still does not provide correct time stamps in  all  cases
1220              in presence of DST - time stamps in a different DST setting will
1221              be off by one hour.
1222
1223       quiet  Turn on the quiet flag.  Attempts to chown or chmod files do not
1224              return errors, although they fail.  Use with caution!
1225
1226       rodir  FAT  has  the  ATTR_RO  (read-only)  attribute.  On Windows, the
1227              ATTR_RO of the directory will just be ignored, and is used  only
1228              by  applications  as  a  flag  (e.g. it's set for the customized
1229              folder).
1230
1231              If you want to use ATTR_RO as read-only flag even for the direc‐
1232              tory, set this option.
1233
1234       showexec
1235              If  set, the execute permission bits of the file will be allowed
1236              only if the extension part of the name is .EXE, .COM,  or  .BAT.
1237              Not set by default.
1238
1239       sys_immutable
1240              If  set,  ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1241              on Linux.  Not set by default.
1242
1243       flush  If set, the filesystem will try to flush to disk more early than
1244              normal.  Not set by default.
1245
1246       usefree
1247              Use  the  "free clusters" value stored on FSINFO.  It'll be used
1248              to determine number of free clusters without scanning disk.  But
1249              it's not used by default, because recent Windows don't update it
1250              correctly in some case.  If you are sure the "free clusters"  on
1251              FSINFO is correct, by this option you can avoid scanning disk.
1252
1253       dots, nodots, dotsOK=[yes|no]
1254              Various misguided attempts to force Unix or DOS conventions onto
1255              a FAT filesystem.
1256
1257
1258   Mount options for hfs
1259       creator=cccc, type=cccc
1260              Set the creator/type values as shown by the  MacOS  finder  used
1261              for creating new files.  Default values: '????'.
1262
1263       uid=n, gid=n
1264              Set the owner and group of all files.  (Default: the UID and GID
1265              of the current process.)
1266
1267       dir_umask=n, file_umask=n, umask=n
1268              Set the umask used for all directories, all  regular  files,  or
1269              all files and directories.  Defaults to the umask of the current
1270              process.
1271
1272       session=n
1273              Select the CDROM session to mount.   Defaults  to  leaving  that
1274              decision  to  the CDROM driver.  This option will fail with any‐
1275              thing but a CDROM as underlying device.
1276
1277       part=n Select partition number n from the device.  Only makes sense for
1278              CDROMs.  Defaults to not parsing the partition table at all.
1279
1280       quiet  Don't complain about invalid mount options.
1281
1282
1283   Mount options for hpfs
1284       uid=value and gid=value
1285              Set  the owner and group of all files. (Default: the UID and GID
1286              of the current process.)
1287
1288       umask=value
1289              Set the umask (the bitmask  of  the  permissions  that  are  not
1290              present).  The default is the umask of the current process.  The
1291              value is given in octal.
1292
1293       case={lower|asis}
1294              Convert all files names to lower case, or leave them.  (Default:
1295              case=lower.)
1296
1297       conv=mode
1298              This option is obsolete and may fail or being ignored.
1299
1300       nocheck
1301              Do not abort mounting when certain consistency checks fail.
1302
1303
1304   Mount options for iso9660
1305       ISO  9660 is a standard describing a filesystem structure to be used on
1306       CD-ROMs. (This filesystem type is also seen on some DVDs.  See also the
1307       udf filesystem.)
1308
1309       Normal  iso9660  filenames  appear  in  an  8.3  format (i.e., DOS-like
1310       restrictions on filename length), and in addition all characters are in
1311       upper  case.   Also  there  is no field for file ownership, protection,
1312       number of links, provision for block/character devices, etc.
1313
1314       Rock Ridge is an extension to iso9660 that provides all of these  UNIX-
1315       like features.  Basically there are extensions to each directory record
1316       that supply all of the additional information, and when Rock  Ridge  is
1317       in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1318       tem (except that it is read-only, of course).
1319
1320       norock Disable the use of Rock Ridge  extensions,  even  if  available.
1321              Cf. map.
1322
1323       nojoliet
1324              Disable  the  use of Microsoft Joliet extensions, even if avail‐
1325              able.  Cf. map.
1326
1327       check={r[elaxed]|s[trict]}
1328              With check=relaxed, a filename is first converted to lower  case
1329              before  doing  the  lookup.   This  is  probably only meaningful
1330              together with norock and map=normal.  (Default: check=strict.)
1331
1332       uid=value and gid=value
1333              Give all files in the filesystem the indicated user or group id,
1334              possibly  overriding  the  information  found  in the Rock Ridge
1335              extensions.  (Default: uid=0,gid=0.)
1336
1337       map={n[ormal]|o[ff]|a[corn]}
1338              For non-Rock Ridge volumes, normal name translation  maps  upper
1339              to  lower case ASCII, drops a trailing `;1', and converts `;' to
1340              `.'.  With map=off no name translation  is  done.   See  norock.
1341              (Default:  map=normal.)   map=acorn  is like map=normal but also
1342              apply Acorn extensions if present.
1343
1344       mode=value
1345              For non-Rock Ridge volumes, give all files the  indicated  mode.
1346              (Default:  read  and  execute  permission for everybody.)  Octal
1347              mode values require a leading 0.
1348
1349       unhide Also show hidden and associated files.  (If the  ordinary  files
1350              and the associated or hidden files have the same filenames, this
1351              may make the ordinary files inaccessible.)
1352
1353       block={512|1024|2048}
1354              Set  the  block  size  to  the   indicated   value.    (Default:
1355              block=1024.)
1356
1357       conv=mode
1358              This option is obsolete and may fail or being ignored.
1359
1360       cruft  If  the high byte of the file length contains other garbage, set
1361              this mount option to ignore the high  order  bits  of  the  file
1362              length.  This implies that a file cannot be larger than 16 MB.
1363
1364       session=x
1365              Select number of session on multisession CD.
1366
1367       sbsector=xxx
1368              Session begins from sector xxx.
1369
1370       The following options are the same as for vfat and specifying them only
1371       makes sense when using discs encoded using  Microsoft's  Joliet  exten‐
1372       sions.
1373
1374       iocharset=value
1375              Character set to use for converting 16 bit Unicode characters on
1376              CD to 8 bit characters.  The default is iso8859-1.
1377
1378       utf8   Convert 16 bit Unicode characters on CD to UTF-8.
1379
1380
1381   Mount options for jfs
1382       iocharset=name
1383              Character set to use for converting from Unicode to ASCII.   The
1384              default  is  to  do  no conversion.  Use iocharset=utf8 for UTF8
1385              translations.  This requires CONFIG_NLS_UTF8 to be  set  in  the
1386              kernel .config file.
1387
1388       resize=value
1389              Resize  the volume to value blocks.  JFS only supports growing a
1390              volume, not shrinking it.  This option is only  valid  during  a
1391              remount, when the volume is mounted read-write.  The resize key‐
1392              word with no value will grow the volume to the full size of  the
1393              partition.
1394
1395       nointegrity
1396              Do  not write to the journal.  The primary use of this option is
1397              to allow for higher performance when  restoring  a  volume  from
1398              backup  media.  The integrity of the volume is not guaranteed if
1399              the system abnormally ends.
1400
1401       integrity
1402              Default.  Commit metadata changes  to  the  journal.   Use  this
1403              option to remount a volume where the nointegrity option was pre‐
1404              viously specified in order to restore normal behavior.
1405
1406       errors={continue|remount-ro|panic}
1407              Define the behavior  when  an  error  is  encountered.   (Either
1408              ignore  errors  and  just mark the filesystem erroneous and con‐
1409              tinue, or remount the filesystem read-only, or  panic  and  halt
1410              the system.)
1411
1412       noquota|quota|usrquota|grpquota
1413              These options are accepted but ignored.
1414
1415
1416   Mount options for msdos
1417       See  mount  options for fat.  If the msdos filesystem detects an incon‐
1418       sistency, it reports an error and sets the file system read-only.   The
1419       filesystem can be made writable again by remounting it.
1420
1421
1422   Mount options for ncpfs
1423       Just  like  nfs,  the ncpfs implementation expects a binary argument (a
1424       struct ncp_mount_data) to the mount system call.  This argument is con‐
1425       structed  by  ncpmount(8)  and the current version of mount (2.12) does
1426       not know anything about ncpfs.
1427
1428
1429   Mount options for ntfs
1430       iocharset=name
1431              Character set to use when returning file  names.   Unlike  VFAT,
1432              NTFS  suppresses  names  that contain nonconvertible characters.
1433              Deprecated.
1434
1435       nls=name
1436              New name for the option earlier called iocharset.
1437
1438       utf8   Use UTF-8 for converting file names.
1439
1440       uni_xlate={0|1|2}
1441              For 0 (or `no' or `false'), do  not  use  escape  sequences  for
1442              unknown  Unicode  characters.   For 1 (or `yes' or `true') or 2,
1443              use vfat-style 4-byte escape sequences starting with ":".   Here
1444              2  give  a  little-endian encoding and 1 a byteswapped bigendian
1445              encoding.
1446
1447       posix=[0|1]
1448              If enabled (posix=1), the filesystem distinguishes between upper
1449              and lower case.  The 8.3 alias names are presented as hard links
1450              instead of being suppressed.  This option is obsolete.
1451
1452       uid=value, gid=value and umask=value
1453              Set the file permission on the filesystem.  The umask  value  is
1454              given in octal.  By default, the files are owned by root and not
1455              readable by somebody else.
1456
1457
1458   Mount options for overlay
1459       Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1460       for other filesystems.
1461
1462       An  overlay  filesystem  combines two filesystems - an upper filesystem
1463       and a lower filesystem.  When a name exists in  both  filesystems,  the
1464       object in the upper filesystem is visible while the object in the lower
1465       filesystem is either hidden or, in the case of directories, merged with
1466       the upper object.
1467
1468       The  lower filesystem can be any filesystem supported by Linux and does
1469       not need to be writable.  The lower  filesystem  can  even  be  another
1470       overlayfs.  The upper filesystem will normally be writable and if it is
1471       it must support the creation of trusted.* extended attributes, and must
1472       provide a valid d_type in readdir responses, so NFS is not suitable.
1473
1474       A read-only overlay of two read-only filesystems may use any filesystem
1475       type.  The options lowerdir and upperdir are  combined  into  a  merged
1476       directory by using:
1477
1478              mount -t overlay  overlay  \
1479                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged
1480
1481
1482       lowerdir=directory
1483              Any filesystem, does not need to be on a writable filesystem.
1484
1485       upperdir=directory
1486              The upperdir is normally on a writable filesystem.
1487
1488       workdir=directory
1489              The  workdir needs to be an empty directory on the same filesys‐
1490              tem as upperdir.
1491
1492
1493   Mount options for reiserfs
1494       Reiserfs is a journaling filesystem.
1495
1496       conv   Instructs version 3.6 reiserfs software to mount a  version  3.5
1497              filesystem,  using  the  3.6  format  for newly created objects.
1498              This filesystem will no longer be compatible with  reiserfs  3.5
1499              tools.
1500
1501       hash={rupasov|tea|r5|detect}
1502              Choose  which  hash  function  reiserfs  will  use to find files
1503              within directories.
1504
1505              rupasov
1506                     A hash invented by Yury Yu. Rupasov.  It is fast and pre‐
1507                     serves  locality,  mapping  lexicographically  close file
1508                     names to close hash values.  This option  should  not  be
1509                     used, as it causes a high probability of hash collisions.
1510
1511              tea    A    Davis-Meyer    function    implemented   by   Jeremy
1512                     Fitzhardinge.  It uses hash permuting bits in  the  name.
1513                     It  gets  high randomness and, therefore, low probability
1514                     of hash collisions at some CPU cost.  This may be used if
1515                     EHASHCOLLISION errors are experienced with the r5 hash.
1516
1517              r5     A  modified  version  of the rupasov hash.  It is used by
1518                     default and is the best choice unless the filesystem  has
1519                     huge directories and unusual file-name patterns.
1520
1521              detect Instructs  mount  to detect which hash function is in use
1522                     by examining the filesystem being mounted, and  to  write
1523                     this  information  into the reiserfs superblock.  This is
1524                     only useful on the first mount of an old format  filesys‐
1525                     tem.
1526
1527       hashed_relocation
1528              Tunes   the  block  allocator.   This  may  provide  performance
1529              improvements in some situations.
1530
1531       no_unhashed_relocation
1532              Tunes  the  block  allocator.   This  may  provide   performance
1533              improvements in some situations.
1534
1535       noborder
1536              Disable  the  border  allocator  algorithm  invented by Yury Yu.
1537              Rupasov.  This may provide performance improvements in some sit‐
1538              uations.
1539
1540       nolog  Disable   journaling.   This  will  provide  slight  performance
1541              improvements in some situations at the cost of losing reiserfs's
1542              fast  recovery  from  crashes.  Even with this option turned on,
1543              reiserfs still performs  all  journaling  operations,  save  for
1544              actual writes into its journaling area.  Implementation of nolog
1545              is a work in progress.
1546
1547       notail By  default,  reiserfs  stores  small  files  and  `file  tails'
1548              directly  into  its  tree.  This confuses some utilities such as
1549              LILO(8).  This option is used to disable packing of  files  into
1550              the tree.
1551
1552       replayonly
1553              Replay  the  transactions  which  are in the journal, but do not
1554              actually mount the filesystem.  Mainly used by reiserfsck.
1555
1556       resize=number
1557              A remount option which permits online expansion of reiserfs par‐
1558              titions.   Instructs reiserfs to assume that the device has num‐
1559              ber blocks.  This option is designed for use with devices  which
1560              are  under  logical volume management (LVM).  There is a special
1561              resizer    utility    which     can     be     obtained     from
1562              ftp://ftp.namesys.com/pub/reiserfsprogs.
1563
1564       user_xattr
1565              Enable Extended User Attributes.  See the attr(1) manual page.
1566
1567       acl    Enable POSIX Access Control Lists.  See the acl(5) manual page.
1568
1569       barrier=none / barrier=flush
1570              This  disables  / enables the use of write barriers in the jour‐
1571              naling  code.   barrier=none  disables,  barrier=flush   enables
1572              (default).   This  also  requires  an IO stack which can support
1573              barriers, and if reiserfs gets an error on a barrier  write,  it
1574              will  disable  barriers  again  with  a warning.  Write barriers
1575              enforce proper  on-disk  ordering  of  journal  commits,  making
1576              volatile  disk  write  caches  safe  to use, at some performance
1577              penalty.  If  your  disks  are  battery-backed  in  one  way  or
1578              another, disabling barriers may safely improve performance.
1579
1580
1581   Mount options for ubifs
1582       UBIFS  is  a  flash filesystem which works on top of UBI volumes.  Note
1583       that atime is not supported and is always turned off.
1584
1585       The device name may be specified as
1586              ubiX_Y UBI device number X, volume number Y
1587
1588              ubiY   UBI device number 0, volume number Y
1589
1590              ubiX:NAME
1591                     UBI device number X, volume with name NAME
1592
1593              ubi:NAME
1594                     UBI device number 0, volume with name NAME
1595       Alternative !  separator may be used instead of :.
1596
1597       The following mount options are available:
1598
1599       bulk_read
1600              Enable bulk-read.  VFS read-ahead is disabled because  it  slows
1601              down  the  file  system.  Bulk-Read is an internal optimization.
1602              Some flashes may read faster if the data are  read  at  one  go,
1603              rather  than at several read requests.  For example, OneNAND can
1604              do "read-while-load" if it reads more than one NAND page.
1605
1606       no_bulk_read
1607              Do not bulk-read.  This is the default.
1608
1609       chk_data_crc
1610              Check data CRC-32 checksums.  This is the default.
1611
1612       no_chk_data_crc.
1613              Do not check data  CRC-32  checksums.   With  this  option,  the
1614              filesystem  does not check CRC-32 checksum for data, but it does
1615              check it for the internal  indexing  information.   This  option
1616              only  affects reading, not writing.  CRC-32 is always calculated
1617              when writing the data.
1618
1619       compr={none|lzo|zlib}
1620              Select the default compressor which is used when new  files  are
1621              written.   It  is  still  possible  to  read compressed files if
1622              mounted with the none option.
1623
1624
1625   Mount options for udf
1626       UDF is the "Universal Disk Format"  filesystem  defined  by  OSTA,  the
1627       Optical  Storage Technology Association, and is often used for DVD-ROM,
1628       frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1629       ever, perfectly usable by itself on disk drives, flash drives and other
1630       block devices.  See also iso9660.
1631
1632       uid=   Make all files in the  filesystem  belong  to  the  given  user.
1633              uid=forget  can  be  specified  independently  of (or usually in
1634              addition to) uid=<user> and results in UDF not storing  uids  to
1635              the  media.  In fact the recorded uid is the 32-bit overflow uid
1636              -1 as defined by the UDF standard.  The value is given as either
1637              <user>  which  is a valid user name or the corresponding decimal
1638              user id, or the special string "forget".
1639
1640       gid=   Make all files in the filesystem  belong  to  the  given  group.
1641              gid=forget  can  be  specified  independently  of (or usually in
1642              addition to) gid=<group> and results in UDF not storing gids  to
1643              the  media.  In fact the recorded gid is the 32-bit overflow gid
1644              -1 as defined by the UDF standard.  The value is given as either
1645              <group> which is a valid group name or the corresponding decimal
1646              group id, or the special string "forget".
1647
1648       umask= Mask out the given permissions from all  inodes  read  from  the
1649              filesystem.  The value is given in octal.
1650
1651       mode=  If mode= is set the permissions of all non-directory inodes read
1652              from the filesystem will be set to the given mode. The value  is
1653              given in octal.
1654
1655       dmode= If  dmode=  is  set the permissions of all directory inodes read
1656              from the filesystem will be set to the given dmode. The value is
1657              given in octal.
1658
1659       bs=    Set the block size. Default value prior to kernel version 2.6.30
1660              was 2048. Since 2.6.30 and prior to 4.11 it was  logical  device
1661              block size with fallback to 2048. Since 4.11 it is logical block
1662              size with fallback to  any  valid  block  size  between  logical
1663              device block size and 4096.
1664
1665              For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1666              PATIBILITY and BLOCK SIZE.
1667
1668       unhide Show otherwise hidden files.
1669
1670       undelete
1671              Show deleted files in lists.
1672
1673       adinicb
1674              Embed data in the inode. (default)
1675
1676       noadinicb
1677              Don't embed data in the inode.
1678
1679       shortad
1680              Use short UDF address descriptors.
1681
1682       longad Use long UDF address descriptors. (default)
1683
1684       nostrict
1685              Unset strict conformance.
1686
1687       iocharset=
1688              Set the NLS character set. This requires  kernel  compiled  with
1689              CONFIG_UDF_NLS option.
1690
1691       utf8   Set the UTF-8 character set.
1692
1693   Mount options for debugging and disaster recovery
1694       novrs  Ignore the Volume Recognition Sequence and attempt to mount any‐
1695              way.
1696
1697       session=
1698              Select the session number  for  multi-session  recorded  optical
1699              media. (default= last session)
1700
1701       anchor=
1702              Override standard anchor location. (default= 256)
1703
1704       lastblock=
1705              Set the last block of the filesystem.
1706
1707   Unused  historical  mount  options  that  may  be encountered and should be
1708       removed
1709       uid=ignore
1710              Ignored, use uid=<user> instead.
1711
1712       gid=ignore
1713              Ignored, use gid=<group> instead.
1714
1715       volume=
1716              Unimplemented and ignored.
1717
1718       partition=
1719              Unimplemented and ignored.
1720
1721       fileset=
1722              Unimplemented and ignored.
1723
1724       rootdir=
1725              Unimplemented and ignored.
1726
1727
1728   Mount options for ufs
1729       ufstype=value
1730              UFS is a filesystem widely used in different operating  systems.
1731              The  problem are differences among implementations.  Features of
1732              some implementations are undocumented, so its hard to  recognize
1733              the type of ufs automatically.  That's why the user must specify
1734              the type of ufs by mount option.  Possible values are:
1735
1736              old    Old format of  ufs,  this  is  the  default,  read  only.
1737                     (Don't forget to give the -r option.)
1738
1739              44bsd  For  filesystems  created  by  a BSD-like system (NetBSD,
1740                     FreeBSD, OpenBSD).
1741
1742              ufs2   Used in FreeBSD 5.x supported as read-write.
1743
1744              5xbsd  Synonym for ufs2.
1745
1746              sun    For filesystems created by SunOS or Solaris on Sparc.
1747
1748              sunx86 For filesystems created by Solaris on x86.
1749
1750              hp     For filesystems created by HP-UX, read-only.
1751
1752              nextstep
1753                     For filesystems created by  NeXTStep  (on  NeXT  station)
1754                     (currently read only).
1755
1756              nextstep-cd
1757                     For NextStep CDROMs (block_size == 2048), read-only.
1758
1759              openstep
1760                     For  filesystems  created  by  OpenStep  (currently  read
1761                     only).  The same filesystem type is also used by  Mac  OS
1762                     X.
1763
1764
1765       onerror=value
1766              Set behavior on error:
1767
1768              panic  If an error is encountered, cause a kernel panic.
1769
1770              [lock|umount|repair]
1771                     These mount options don't do anything at present; when an
1772                     error is encountered only a console message is printed.
1773
1774
1775   Mount options for umsdos
1776       See mount options for msdos.  The dotsOK option is explicitly killed by
1777       umsdos.
1778
1779
1780   Mount options for vfat
1781       First  of  all,  the  mount options for fat are recognized.  The dotsOK
1782       option is explicitly killed by vfat.  Furthermore, there are
1783
1784       uni_xlate
1785              Translate  unhandled  Unicode  characters  to  special   escaped
1786              sequences.   This lets you backup and restore filenames that are
1787              created with any Unicode characters.  Without this option, a '?'
1788              is  used  when no translation is possible.  The escape character
1789              is ':' because it is otherwise invalid on the  vfat  filesystem.
1790              The escape sequence that gets used, where u is the Unicode char‐
1791              acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1792
1793       posix  Allow two files with names  that  only  differ  in  case.   This
1794              option is obsolete.
1795
1796       nonumtail
1797              First  try  to make a short name without sequence number, before
1798              trying name~num.ext.
1799
1800       utf8   UTF8 is the filesystem safe 8-bit encoding of  Unicode  that  is
1801              used  by the console.  It can be enabled for the filesystem with
1802              this option or disabled with utf8=0, utf8=no or utf8=false.   If
1803              `uni_xlate' gets set, UTF8 gets disabled.
1804
1805       shortname=mode
1806              Defines the behavior for creation and display of filenames which
1807              fit into 8.3 characters.  If a long name for a file  exists,  it
1808              will  always  be  the preferred one for display.  There are four
1809              modes:
1810
1811              lower  Force the short name to lower case upon display; store  a
1812                     long name when the short name is not all upper case.
1813
1814              win95  Force  the short name to upper case upon display; store a
1815                     long name when the short name is not all upper case.
1816
1817              winnt  Display the short name as is; store a long name when  the
1818                     short name is not all lower case or all upper case.
1819
1820              mixed  Display  the short name as is; store a long name when the
1821                     short name is not all  upper  case.   This  mode  is  the
1822                     default since Linux 2.6.32.
1823
1824
1825   Mount options for usbfs
1826       devuid=uid and devgid=gid and devmode=mode
1827              Set  the  owner  and  group  and mode of the device files in the
1828              usbfs filesystem (default: uid=gid=0, mode=0644).  The  mode  is
1829              given in octal.
1830
1831       busuid=uid and busgid=gid and busmode=mode
1832              Set  the  owner and group and mode of the bus directories in the
1833              usbfs filesystem (default: uid=gid=0, mode=0555).  The  mode  is
1834              given in octal.
1835
1836       listuid=uid and listgid=gid and listmode=mode
1837              Set  the  owner and group and mode of the file devices (default:
1838              uid=gid=0, mode=0444).  The mode is given in octal.
1839
1840

DM-VERITY SUPPORT (experimental)

1842       The  device-mapper  verity  target   provides   read-only   transparent
1843       integrity checking of block devices using kernel crypto API.  The mount
1844       command can open the dm-verity device and do the integrity verification
1845       before  on  the  device  filesystem is mounted.  Requires libcryptsetup
1846       with in libmount.  If libcryptsetup supports extracting the  root  hash
1847       of  an  already  mounted device, existing devices will be automatically
1848       reused in case of a match.  Mount options for dm-verity:
1849
1850       verity.hashdevice=path
1851              Path to the hash tree device associated with the  source  volume
1852              to pass to dm-verity.
1853
1854       verity.roothash=hex
1855              Hex-encoded  hash  of  the  root  of  verity.hashdevice Mutually
1856              exclusive with verity.roothashfile.
1857
1858       verity.roothashfile=path
1859              Path to file containing the hex-encoded hash of the root of ver‐
1860              ity.hashdevice.  Mutually exclusive with verity.roothash.
1861
1862       verity.hashoffset=offset
1863              If the hash tree device is embedded in the source volume, offset
1864              (default: 0) is used by dm-verity to get to the tree.
1865
1866       verity.fecdevice=path
1867              Path to the Forward Error  Correction  (FEC)  device  associated
1868              with the source volume to pass to dm-verity.  Optional. Requires
1869              kernel built with CONFIG_DM_VERITY_FEC.
1870
1871       verity.fecoffset=offset
1872              If the FEC device is  embedded  in  the  source  volume,  offset
1873              (default:  0)  is  used  by  dm-verity  to  get to the FEC area.
1874              Optional.
1875
1876       verity.fecroots=value
1877              Parity bytes for FEC (default: 2). Optional.
1878
1879       Supported since util-linux v2.35.
1880
1881       For example commands:
1882
1883              mksquashfs /etc /tmp/etc.squashfs
1884              dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
1885              veritysetup format /tmp/etc.squashfs /tmp/etc.hash
1886              mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash> /tmp/etc.squashfs /mnt
1887
1888       create squashfs image from /etc directory, verity hash device and mount
1889       verified filesystem image to /mnt.
1890
1891

LOOP-DEVICE SUPPORT

1893       One further possible type is a mount via the loop device.  For example,
1894       the command
1895
1896              mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1897
1898       will set up the loop  device  /dev/loop3  to  correspond  to  the  file
1899       /tmp/disk.img, and then mount this device on /mnt.
1900
1901       If  no  explicit loop device is mentioned (but just an option `-o loop'
1902       is given), then mount will try to find some unused loop device and  use
1903       that, for example
1904
1905              mount /tmp/disk.img /mnt -o loop
1906
1907       The  mount  command  automatically creates a loop device from a regular
1908       file if a filesystem type is not specified or the filesystem  is  known
1909       for libblkid, for example:
1910
1911              mount /tmp/disk.img /mnt
1912
1913              mount -t ext4 /tmp/disk.img /mnt
1914
1915       This  type  of mount knows about three options, namely loop, offset and
1916       sizelimit, that are really options to losetup(8).  (These  options  can
1917       be used in addition to those specific to the filesystem type.)
1918
1919       Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1920       ing that any loop device allocated by mount will  be  freed  by  umount
1921       independently of /etc/mtab.
1922
1923       You can also free a loop device by hand, using losetup -d or umount -d.
1924
1925       Since  util-linux  v2.29  mount  command re-uses the loop device rather
1926       than initialize a new device if the same backing file is  already  used
1927       for some loop device with the same offset and sizelimit. This is neces‐
1928       sary to avoid a filesystem corruption.
1929
1930

RETURN CODES

1932       mount has the following return codes (the bits can be ORed):
1933
1934       0      success
1935
1936       1      incorrect invocation or permissions
1937
1938       2      system error (out of memory, cannot fork, no more loop devices)
1939
1940       4      internal mount bug
1941
1942       8      user interrupt
1943
1944       16     problems writing or locking /etc/mtab
1945
1946       32     mount failure
1947
1948       64     some mount succeeded
1949
1950              The command mount -a returns 0 (all succeeded), 32 (all failed),
1951              or 64 (some failed, some succeeded).
1952
1953

EXTERNAL HELPERS

1955       The syntax of external mount helpers is:
1956
1957           /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
1958           type.subtype]
1959
1960       where the suffix is the filesystem type and the  -sfnvoN  options  have
1961       the  same  meaning  as the normal mount options.  The -t option is used
1962       for filesystems with subtypes support (for example /sbin/mount.fuse  -t
1963       fuse.sshfs).
1964
1965       The  command mount does not pass the mount options unbindable, runbind‐
1966       able, private, rprivate, slave, rslave, shared, rshared, auto,  noauto,
1967       comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
1968       All other options are used in a comma-separated list as argument to the
1969       -o option.
1970
1971

FILES

1973       See  also  "The  files  /etc/fstab, /etc/mtab and /proc/mounts" section
1974       above.
1975
1976       /etc/fstab        filesystem table
1977
1978       /run/mount        libmount private runtime directory
1979
1980       /etc/mtab         table  of   mounted   filesystems   or   symlink   to
1981                         /proc/mounts
1982
1983       /etc/mtab~        lock file (unused on systems with mtab symlink)
1984
1985       /etc/mtab.tmp     temporary file (unused on systems with mtab symlink)
1986
1987       /etc/filesystems  a list of filesystem types to try
1988

ENVIRONMENT

1990       LIBMOUNT_FSTAB=<path>
1991              overrides  the  default  location of the fstab file (ignored for
1992              suid)
1993
1994       LIBMOUNT_MTAB=<path>
1995              overrides the default location of the  mtab  file  (ignored  for
1996              suid)
1997
1998       LIBMOUNT_DEBUG=all
1999              enables libmount debug output
2000
2001       LIBBLKID_DEBUG=all
2002              enables libblkid debug output
2003
2004       LOOPDEV_DEBUG=all
2005              enables loop device setup debug output
2006

SEE ALSO

2008       mount(2), umount(2), umount(8), fstab(5), nfs(5), xfs(5), e2label(8),
2009       findmnt(8), losetup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8),
2010       tune2fs(8), xfs_admin(8)
2011

BUGS

2013       It is possible for a corrupted filesystem to cause a crash.
2014
2015       Some  Linux filesystems don't support -o sync nor -o dirsync (the ext2,
2016       ext3, ext4, fat and vfat filesystems do support synchronous updates  (a
2017       la BSD) when mounted with the sync option).
2018
2019       The  -o remount may not be able to change mount parameters (all ext2fs-
2020       specific parameters, except sb, are  changeable  with  a  remount,  for
2021       example, but you can't change gid or umask for the fatfs).
2022
2023       It is possible that the files /etc/mtab and /proc/mounts don't match on
2024       systems with a regular mtab file.  The first file is based only on  the
2025       mount  command options, but the content of the second file also depends
2026       on the kernel and others settings (e.g. on a remote NFS  server  --  in
2027       certain cases the mount command may report unreliable information about
2028       an NFS mount point and the  /proc/mounts  file  usually  contains  more
2029       reliable information.)  This is another reason to replace the mtab file
2030       with a symlink to the /proc/mounts file.
2031
2032       Checking files on NFS filesystems referenced by file descriptors  (i.e.
2033       the  fcntl  and  ioctl  families of functions) may lead to inconsistent
2034       results due to the lack of a consistency check in the  kernel  even  if
2035       noac is used.
2036
2037       The loop option with the offset or sizelimit options used may fail when
2038       using older kernels if the mount command can't confirm that the size of
2039       the  block device has been configured as requested.  This situation can
2040       be worked around by using the losetup command manually  before  calling
2041       mount with the configured loop device.
2042

HISTORY

2044       A mount command existed in Version 5 AT&T UNIX.
2045

AUTHORS

2047       Karel Zak <kzak@redhat.com>
2048

AVAILABILITY

2050       The  mount  command  is part of the util-linux package and is available
2051       from https://www.kernel.org/pub/linux/utils/util-linux/.
2052
2053
2054
2055util-linux                        August 2015                         MOUNT(8)
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