linux命令之-mount

[root@localhost ~]# man mount
MOUNT(8)                   Linux Programmer’s Manual                  MOUNT(8)

NAME
       mount - mount a file system

SYNOPSIS
       mount [-lhV]

       mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
       mount [-fnrsvw] [-o options [,...]] device | dir
       mount [-fnrsvw] [-t vfstype] [-o options] device dir

DESCRIPTION
       All  files  accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /.  These
       files can be spread out over several devices. The mount command serves to attach the  file  system  found  on
       some device to the big file tree. Conversely, the umount(8) command will detach it again.

       The standard form of the mount command, is
              mount -t type device dir
       This tells the kernel to attach the file system found on device (which is of type type) at the directory dir.
       The previous contents (if any) and owner and mode of dir become invisible, and as long as  this  file  system
       remains mounted, the pathname dir refers to the root of the file system on device.

       Three forms of invocation do not actually mount anything:
              mount -h
       prints a help message;
              mount -V
       prints a version string; and just
              mount [-l] [-t type]
       lists  all  mounted  file systems (of type type).  The option -l adds the (ext2, ext3 and XFS) labels in this
       listing.  See below.

       Since Linux 2.4.0 it is possible to remount part of the file hierarchy somewhere else. The call is
              mount --bind olddir newdir
       After this call the same contents is accessible in two places.  One can also remount a single file (on a sin-
       gle file).

       This  call  attaches  only  (part  of) a single filesystem, not possible submounts. The entire file hierarchy
       including submounts is attached a second place using
              mount --rbind olddir newdir

       Note that the filesystem mount options will remain the same as those on the original mount point, and  cannot
       be changed by passing the -o option along with --bind/--rbind.

       Since Linux 2.5.1 it is possible to atomically move a mounted tree to another place. The call is
              mount --move olddir newdir

       Since  Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable.
       A shared mount provides ability to create mirrors of that mount such that mounts and umounts  within  any  of
       the  mirrors  propagate  to the other mirror. A slave mount receives propagation from its master, but any not
       vice-versa.  A private mount carries no propagation abilities.  A unbindable mount is a private  mount  which
       cannot  cloned  through a bind operation. Detailed semantics is documented in Documentation/sharedsubtree.txt
       file in the kernel source tree.
              mount --make-shared mountpoint
              mount --make-slave mountpoint
              mount --make-private mountpoint
              mount --make-unbindable mountpoint

       The following commands allows one to recursively change the type of all the mounts under a given  mountpoint.
              mount --make-rshared mountpoint
              mount --make-rslave mountpoint
              mount --make-rprivate mountpoint
              "mount --make-runbindable mountpoint"

       The  proc  file  system  is not associated with a special device, and when mounting it, an arbitrary keyword,
       such as proc can be used instead of a device specification.  (The customary choice none  is  less  fortunate:
       the error message ‘none busy’ from umount can be confusing.)

       Most  devices  are  indicated by a file name (of a block special device), like /dev/sda1, but there are other
       possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir.  It is  pos-
       sible to indicate a block special device using its volume label or UUID (see the -L and -U options below).

       The  file  /etc/fstab  (see  fstab(5)),  may contain lines describing what devices are usually mounted where,
       using which options. This file is used in three ways:

       (i) The command
              mount -a [-t type] [-O optlist]
       (usually given in a bootscript) causes all file systems mentioned in fstab (of the proper type and/or  having
       or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto
       keyword. Adding the -F option will make mount fork, so that the filesystems are mounted simultaneously.

       (ii) When mounting a file system mentioned in fstab, it suffices to give only the device, or only  the  mount
       point.

       (iii) Normally, only the superuser can mount file systems.  However, when fstab contains the user option on a
       line, anybody can mount the corresponding system.

       Thus, given a line
              /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide
       any user can mount the iso9660 file system found on his CDROM using the command
              mount /dev/cdrom
       or
              mount /cd
       For more details, see fstab(5).  Only the user that mounted a filesystem can unmount it again.  If  any  user
       should  be able to unmount, then use users instead of user in the fstab line.  The owner option is similar to
       the user option, with the restriction that the user must be the owner of the special file. This may be useful
       e.g. for /dev/fd if a login script makes the console user owner of this device.  The group option is similar,
       with the restriction that the user must be member of the group of the special file.

       The programs mount and umount maintain a list of currently mounted file systems in the file /etc/mtab.  If no
       arguments are given to mount, this list is printed.

       When  the  proc  filesystem is mounted (say at /proc), the files /etc/mtab and /proc/mounts have very similar
       contents. The former has somewhat more information, such as the mount options used, but  is  not  necessarily
       up-to-date (cf. the -n option below). It is possible to replace /etc/mtab by a symbolic link to /proc/mounts,
       and especially when you have very large numbers of mounts things will be much faster with that  symlink,  but
       some  information  is  lost that way, and in particular working with the loop device will be less convenient,
       and using the "user" option will fail.

OPTIONS
       The full set of options used by an invocation of mount is determined by first extracting the options for  the
       file  system from the fstab table, then applying any options specified by the -o argument, and finally apply-
       ing a -r or -w option, when present.

       Options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

       -a     Mount all filesystems (of the given types) mentioned in fstab.

       -F     (Used in conjunction with -a.)  Fork off a new incarnation of mount for each device.  This will do the
              mounts  on  different devices or different NFS servers in parallel.  This has the advantage that it is
              faster; also NFS timeouts go in parallel. A disadvantage is that the  mounts  are  done  in  undefined
              order.  Thus, you cannot use this option if you want to mount both /usr and /usr/spool.

       -f     Causes  everything  to  be done except for the actual system call; if it’s not obvious, this ‘‘fakes’’
              mounting the file system.  This option is useful in conjunction with the -v flag to determine what the
              mount  command  is trying to do. It can also be used to add entries for devices that were mounted ear-
              lier with the -n option.

       -i     Don’t call the /sbin/mount.<filesystem> helper even if it exists.

       -l     Add the ext2, ext3 and XFS labels in the mount output. Mount must have permission  to  read  the  disk
              device  (e.g.  be  suid  root)  for this to work.  One can set such a label for ext2 or ext3 using the
              e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8).

       -n     Mount without writing in /etc/mtab.  This is necessary for example when /etc is on  a  read-only  file
              system.

       -p num In  case of a loop mount with encryption, read the passphrase from file descriptor num instead of from
              the terminal.

       -s     Tolerate sloppy mount options rather than failing. This will ignore mount options not supported  by  a
              filesystem  type. Not all filesystems support this option. This option exists for support of the Linux
              autofs-based automounter.

       -r     Mount the file system read-only. A synonym is -o ro.

       -w     Mount the file system read/write. This is the default. A synonym is -o rw.

       -L label
              Mount the partition that has the specified label.

       -U uuid
              Mount the partition that has the specified uuid.  These two options require the file  /proc/partitions
              (present since Linux 2.1.116) to exist.

       -t vfstype
              The  argument  following the -t is used to indicate the file system type.  The file system types which
              are currently supported include: adfs, affs, autofs, cifs, coda, coherent,  cramfs,  debugfs,  devpts,
              efs,  ext,  ext2,  ext3,  hfs,  hpfs,  iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc, qnx4,
              ramfs, reiserfs, romfs, smbfs, sysv, tmpfs, udf, ufs, umsdos, usbfs, vfat, xenix,  xfs,  xiafs.   Note
              that coherent, sysv and xenix are equivalent and that xenix and coherent will be removed at some point
              in the future — use sysv instead. Since kernel version 2.1.21 the types ext and  xiafs  do  not  exist
              anymore. Earlier, usbfs was known as usbdevfs.

              For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed
              knowledge of the filesystem type is required.  For a few types however (like nfs, nfs4,  cifs,  smbfs,
              ncpfs)  ad  hoc  code is necessary. The nfs ad hoc code is built in, but cifs, smbfs, and ncpfs have a
              separate mount program. In order to make it possible to treat all types in a uniform way,  mount  will
              execute  the program /sbin/mount.TYPE (if that exists) when called with type TYPE.  Since various ver-
              sions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to  be  a
              shell script that sets up the desired call.

              If  no -t option is given, or if the auto type is specified, mount will try to guess the desired type.
              If mount was compiled with the blkid library, the guessing is done by this library.  Otherwise,  mount
              guesses itself by probing the superblock; if that does not turn up anything that looks familiar, mount
              will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems.  All of the
              filesystem  types listed there will be tried, except for those that are labeled "nodev" (e.g., devpts,
              proc, nfs, and nfs4).  If /etc/filesystems ends in a line with  a  single  *  only,  mount  will  read
              /proc/filesystems afterwards.

              The auto type may be useful for user-mounted floppies.  Creating a file /etc/filesystems can be useful
              to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a  kernel
              module  autoloader.   Warning: the probing uses a heuristic (the presence of appropriate ‘magic’), and
              could recognize the wrong filesystem type, possibly with catastrophic consequences. If  your  data  is
              valuable, don’t ask mount to guess.

              More  than  one type may be specified in a comma separated list.  The list of file system types can be
              prefixed with no to specify the file system types on which no action should be taken.   (This  can  be
              meaningful with the -a option.)

              For example, the command:
                     mount -a -t nomsdos,ext
              mounts all file systems except those of type msdos and ext.

       -O     Used  in  conjunction with -a, to limit the set of filesystems to which the -a is applied.  Like -t in
              this regard except that it is useless except in the context of -a.  For example, the command:
                     mount -a -O no_netdev
              mounts all file systems except those which have the option _netdev specified in the options  field  in
              the /etc/fstab file.

              It  is  different from -t in that each option is matched exactly; a leading no at the beginning of one
              option does not negate the rest.

              The -t and -O options are cumulative in effect; that is, the command
                     mount -a -t ext2 -O _netdev
              mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or  have
              the _netdev option specified.

       -o     Options  are  specified with a -o flag followed by a comma separated string of options.  Some of these
              options are only useful when they appear in the /etc/fstab file.  The following options apply  to  any
              file  system  that  is  being mounted (but not every file system actually honors them - e.g., the sync
              option today has effect only for ext2, ext3, fat, vfat and ufs):

              async  All I/O to the file system should be done asynchronously.

              atime  Update inode access time for each access. This is the default.

              auto   Can be mounted with the -a option.

              defaults
                     Use default options: rw, suid, dev, exec, auto, nouser, and async.

              dev    Interpret character or block special devices on the file system.

              exec   Permit execution of binaries.

              group  Allow an ordinary (i.e., non-root) user to mount the file system if one of his  groups  matches
                     the  group  of the device.  This option implies the options nosuid and nodev (unless overridden
                     by subsequent options, as in the option line group,dev,suid).

              mand   Allow mandatory locks on this filesystem. See fcntl(2).

              _netdev
                     The filesystem resides on a device that requires network access (used  to  prevent  the  system
                     from attempting to mount these filesystems until the network has been enabled on the system).

              noatime
                     Do  not update inode access times on this file system (e.g, for faster access on the news spool
                     to speed up news servers).

              nodiratime
                     Do not update directory inode access times on this filesystem.

              noauto Can only be mounted explicitly (i.e., the -a option will  not  cause  the  file  system  to  be
                     mounted).

              nodev  Do not interpret character or block special devices on the file system.

              noexec Do  not  allow direct execution of any binaries on the mounted file system.  (Until recently it
                     was possible to run binaries anyway using a command like /lib/ld*.so  /mnt/binary.  This  trick
                     fails since Linux 2.4.25 / 2.6.0.)

              nomand Do not allow mandatory locks on this filesystem.

              nosuid Do not allow set-user-identifier or set-group-identifier bits to take effect. (This seems safe,
                     but is in fact rather unsafe if you have suidperl(1) installed.)

              nouser Forbid an ordinary (i.e., non-root) user to mount the file system.  This is the default.

              owner  Allow an ordinary (i.e., non-root) user to mount the file system if he  is  the  owner  of  the
                     device.   This  option  implies  the  options nosuid and nodev (unless overridden by subsequent
                     options, as in the option line owner,dev,suid).

              remount
                     Attempt to remount an already-mounted file system.  This is commonly used to change  the  mount
                     flags  for  a  file  system,  especially  to make a readonly file system writeable. It does not
                     change device or mount point.

              ro     Mount the file system read-only.

              _rnetdev
                     Like _netdev, except "fsck -a" checks this filesystem during rc.sysinit.

              rw     Mount the file system read-write.

              suid   Allow set-user-identifier or set-group-identifier bits to take effect.

              sync   All I/O to the file system should be done synchronously. In case of media with  limited  number
                     of write cycles (e.g. some flash drives) "sync" may cause life-cycle shortening.

              dirsync
                     All  directory  updates  within the file system should be done synchronously.  This affects the
                     following system calls: creat, link, unlink, symlink, mkdir, rmdir, mknod and rename.

              user   Allow an ordinary user to mount the file system.  The name of the mounting user is  written  to
                     mtab  so  that  he  can unmount the file system again.  This option implies the options noexec,
                     nosuid,  and  nodev  (unless  overridden  by  subsequent  options,  as  in  the   option   line
                     user,exec,dev,suid).

              users  Allow every user to mount and unmount the file system.  This option implies the options noexec,
                     nosuid,  and  nodev  (unless  overridden  by  subsequent  options,  as  in  the   option   line
                     users,exec,dev,suid).

              context=context, fscontext=context and defcontext=context
                     The  context=  option  is  useful  when  mounting  filesystems  that  do  not  support extended
                     attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally
                     running  under  SELinux, such as an ext3 formatted disk from a non-SELinux workstation. You can
                     also use context= on filesystems you do not trust, such as a floppy. It also helps in  compati-
                     bility  with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs
                     are supported, you can save time not having to label every file by assigning  the  entire  disk
                     one security context.

                     A commonly used option for removable media is context=system_u:object_r:removable_t.

                     Two  other  options are fscontext= and defcontext=, both of which are mutually exclusive of the
                     context option. This means you can use fscontext and defcontext with each  other,  but  neither
                     can be used with context.

                     The  fscontext= option works for all filesystems, regardless of their xattr support. The fscon-
                     text option sets the overarching filesystem label to a specific security context. This filesys-
                     tem  label  is  separate  from  the  individual  labels  on the files. It represents the entire
                     filesystem for certain kinds of permission checks, such  as  during  mount  or  file  creation.
                     Individual  file labels are still obtained from the xattrs on the files themselves. The context
                     option actually sets the aggregate context that fscontext provides, in  addition  to  supplying
                     the same label for individual files.

                     You  can  set  the  default security context for unlabeled files using defcontext= option. This
                     overrides the value set for unlabeled files in the policy and requires a file system that  sup-
                     ports xattr labeling.

                     For more details see selinux(8)

       --bind Remount a subtree somewhere else (so that its contents are available in both places). See above.

       --move Move a subtree to some other place. See above.

FILESYSTEM SPECIFIC MOUNT OPTIONS
       The  following  options apply only to certain file systems.  We sort them by file system. They all follow the
       -o flag.

       What options are supported depends a bit on the running kernel.  More info may be found in the kernel  source
       subdirectory Documentation/filesystems.

Mount options for adfs
       uid=value and gid=value
              Set the owner and group of the files in the file system (default: uid=gid=0).

       ownmask=value and othmask=value
              Set  the  permission mask for ADFS ’owner’ permissions and ’other’ permissions, respectively (default:
              0700 and 0077, respectively).  See also /usr/src/linux/Documentation/filesystems/adfs.txt.

Mount options for affs
       uid=value and gid=value
              Set the owner and group of the root of the file system (default: uid=gid=0, but with option uid or gid
              without specified value, the uid and gid of the current process are taken).

       setuid=value and setgid=value
              Set the owner and group of all files.

       mode=value
              Set  the  mode of all files to value & 0777 disregarding the original permissions.  Add search permis-
              sion to directories that have read permission.  The value is given in octal.

       protect
              Do not allow any changes to the protection bits on the file system.

       usemp  Set uid and gid of the root of the file system to the uid and gid of the mount point  upon  the  first
              sync or umount, and then clear this option. Strange...

       verbose
              Print an informational message for each successful mount.

       prefix=string
              Prefix used before volume name, when following a link.

       volume=string
              Prefix (of length at most 30) used before ’/’ when following a symbolic link.

       reserved=value
              (Default: 2.) Number of unused blocks at the start of the device.

       root=value
              Give explicitly the location of the root block.

       bs=value
              Give blocksize. Allowed values are 512, 1024, 2048, 4096.

       grpquota / noquota / quota / usrquota
              These  options  are  accepted  but  ignored.   (However,  quota utilities may react to such strings in
              /etc/fstab.)

Mount options for cifs
       See the options section of the mount.cifs(8) man page (cifs-mount package must be installed).

Mount options for cifs
       Just like nfs or smbfs implementation expects a binary argument to the mount system call.  This  argument  is
       constructed by mount.cifs(8) and the current version of mount (2.12) does not know anything about cifs.

Mount options for coherent
       None.

Mount options for debugfs
       The  debugfs  file  system is a pseudo file system, traditionally mounted on /sys/kernel/debug.  There are no
       mount options.

Mount options for devpts
       The devpts file system is a pseudo file system, traditionally mounted on /dev/pts.  In  order  to  acquire  a
       pseudo  terminal,  a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the
       process and the pseudo terminal slave can be accessed as /dev/pts/<number>.

       uid=value and gid=value
              This sets the owner or the group of newly created PTYs to the specified values. When nothing is speci-
              fied,  they  will  be  set to the UID and GID of the creating process.  For example, if there is a tty
              group with GID 5, then gid=5 will cause newly created PTYs to belong to the tty group.

       mode=value
              Set the mode of newly created PTYs to the specified value.  The default is 0600.  A value of  mode=620
              and gid=5 makes "mesg y" the default on newly created PTYs.

Mount options for ext
       None.   Note  that  the  ‘ext’ file system is obsolete. Don’t use it.  Since Linux version 2.1.21 extfs is no
       longer part of the kernel source.

Mount options for ext2
       The ‘ext2’ file system is the standard Linux file system.  Since Linux 2.5.46, for  most  mount  options  the
       default is determined by the filesystem superblock. Set them with tune2fs(8).

       acl / noacl
              Support POSIX Access Control Lists (or not).

       bsddf / minixdf
              Set the behaviour for the statfs system call. The minixdf behaviour is to return in the f_blocks field
              the total number of blocks of the file system, while the bsddf behaviour (which is the default) is  to
              subtract the overhead blocks used by the ext2 file system and not available for file storage. Thus

       % mount /k -o minixdf; df /k; umount /k
       Filesystem   1024-blocks  Used Available Capacity Mounted on
       /dev/sda6      2630655   86954  2412169      3%   /k
       % mount /k -o bsddf; df /k; umount /k
       Filesystem   1024-blocks  Used Available Capacity Mounted on
       /dev/sda6      2543714      13  2412169      0%   /k

       (Note that this example shows that one can add command line options to the options given in /etc/fstab.)

       check=none / nocheck
              No  checking is done at mount time. This is the default. This is fast.  It is wise to invoke e2fsck(8)
              every now and then, e.g. at boot time.

       debug  Print debugging info upon each (re)mount.

       errors=continue / errors=remount-ro / errors=panic
              Define the behaviour when an error is encountered.  (Either ignore errors and just mark the file  sys-
              tem  erroneous and continue, or remount the file system read-only, or panic and halt the system.)  The
              default is set in the filesystem superblock, and can be changed using tune2fs(8).

       grpid or bsdgroups / nogrpid or sysvgroups
              These options define what group id a newly created file gets.  When grpid is set, it takes  the  group
              id  of the directory in which it is created; otherwise (the default) it takes the fsgid of the current
              process, unless the directory has the setgid bit set, in which case it takes the gid from  the  parent
              directory, and also gets the setgid bit set if it is a directory itself.

       grpquota / noquota / quota / usrquota
              These options are accepted but ignored.

       nobh   Do not attach buffer_heads to file pagecache. (Since 2.5.49.)

       nouid32
              Disables  32-bit  UIDs and GIDs.  This is for interoperability with older kernels which only store and
              expect 16-bit values.

       oldalloc or orlov
              Use old allocator or Orlov allocator for new inodes. Orlov is default.

       resgid=n and resuid=n
              The ext2 file system reserves a certain  percentage  of  the  available  space  (by  default  5%,  see
              mke2fs(8)  and  tune2fs(8)).  These options determine who can use the reserved blocks.  (Roughly: who-
              ever has the specified uid, or belongs to the specified group.)

       sb=n   Instead of block 1, use block n as superblock. This could be useful when the filesystem has been  dam-
              aged.   (Earlier,  copies  of the superblock would be made every 8192 blocks: in block 1, 8193, 16385,
              ... (and one got thousands of copies on a big filesystem). Since version 1.08, mke2fs has a -s (sparse
              superblock)  option  to  reduce  the  number of backup superblocks, and since version 1.15 this is the
              default. Note that this may mean that ext2 filesystems created by a recent mke2fs  cannot  be  mounted
              r/w  under  Linux 2.0.*.)  The block number here uses 1k units. Thus, if you want to use logical block
              32768 on a filesystem with 4k blocks, use "sb=131072".

       user_xattr / nouser_xattr
              Support "user." extended attributes (or not).

Mount options for ext3
       The ‘ext3’ file system is a version of the ext2 file system which has been  enhanced  with  journalling.   It
       supports the same options as ext2 as well as the following additions:

       journal=update
              Update the ext3 file system’s journal to the current format.

       journal=inum
              When a journal already exists, this option is ignored. Otherwise, it specifies the number of the inode
              which will represent the ext3 file system’s journal file;  ext3 will create a new journal, overwriting
              the old contents of the file whose inode number is inum.

       noload Do not load the ext3 file system’s journal on mounting.

       data=journal / data=ordered / data=writeback
              Specifies  the journalling mode for file data.  Metadata is always journaled.  To use modes other than
              ordered on the root file system,  pass  the  mode  to  the  kernel  as  boot  parameter,  e.g.   root-
              flags=data=journal.

              journal
                     All data is committed into the journal prior to being written into the main file system.

              ordered
                     This is the default mode.  All data is forced directly out to the main file system prior to its
                     metadata being committed to the journal.

              writeback
                     Data ordering is not preserved - data may be written into the main file system after its  meta-
                     data  has been committed to the journal.  This is rumoured to be the highest-throughput option.
                     It guarantees internal file system integrity, however it can allow old data to appear in  files
                     after a crash and journal recovery.

       commit=nrsec
              Sync all data and metadata every nrsec seconds. The default value is 5 seconds. Zero means default.

Mount options for fat
       (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.)

       blocksize=512 / blocksize=1024 / blocksize=2048
              Set blocksize (default 512).

       uid=value and gid=value
              Set the owner and group of all files.  (Default: the uid and gid of the current process.)

       umask=value
              Set  the  umask (the bitmask of the permissions that are not present). The default is the umask of the
              current process.  The value is given in octal.

       dmask=value
              Set the umask applied to directories only.  The default is the umask  of  the  current  process.   The
              value is given in octal.

       fmask=value
              Set  the  umask  applied to regular files only.  The default is the umask of the current process.  The
              value is given in octal.

       check=value
              Three different levels of pickyness can be chosen:

              r[elaxed]
                     Upper and lower case are accepted and equivalent, long name parts are  truncated  (e.g.   very-
                     longname.foobar  becomes  verylong.foo),  leading and embedded spaces are accepted in each name
                     part (name and extension).

              n[ormal]
                     Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected.  This is  the
                     default.

              s[trict]
                     Like  "normal",  but names may not contain long parts and special characters that are sometimes
                     used on Linux, but are not accepted by MS-DOS are rejected. (+, =, spaces, etc.)

       codepage=value
              Sets the codepage for converting to shortname characters on FAT  and  VFAT  filesystems.  By  default,
              codepage 437 is used.

       conv=b[inary] / conv=t[ext] / conv=a[uto]
              The  fat file system can perform CRLF<-->NL (MS-DOS text format to UNIX text format) conversion in the
              kernel. The following conversion modes are available:

              binary no translation is performed.  This is the default.

              text   CRLF<-->NL translation is performed on all files.

              auto   CRLF<-->NL translation is performed on all files that don’t have a "well-known  binary"  exten-
                     sion.  The  list of known extensions can be found at the beginning of fs/fat/misc.c (as of 2.0,
                     the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj, lib, dll, pif, arc,  zip,  lha,  lzh,
                     zoo,  tar,  z,  arj, tz, taz, tzp, tpz, gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf,
                     pk, pxl, dvi).

              Programs that do computed lseeks won’t like in-kernel text conversion.  Several people have had  their
              data ruined by this translation. Beware!

              For file systems mounted in binary mode, a conversion tool (fromdos/todos) is available.

       cvf_format=module
              Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection.
              If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading.

       cvf_option=option
              Option passed to the CVF module.

       debug  Turn on the debug flag.  A version string and a list of file system parameters will be printed  (these
              data are also printed if the parameters appear to be inconsistent).

       fat=12 / fat=16 / fat=32
              Specify  a  12,  16 or 32 bit fat.  This overrides the automatic FAT type detection routine.  Use with
              caution!

       iocharset=value
              Character set to use for converting between 8 bit  characters  and  16  bit  Unicode  characters.  The
              default is iso8859-1.  Long filenames are stored on disk in Unicode format.

       quiet  Turn  on  the  quiet flag.  Attempts to chown or chmod files do not return errors, although they fail.
              Use with caution!

       sys_immutable, showexec, dots, nodots, dotsOK=[yes|no]
              Various misguided attempts to force Unix or DOS conventions onto a FAT file system.

Mount options for hfs
       creator=cccc, type=cccc
              Set the creator/type values as shown by the MacOS finder used for creating new files.  Default values:
              ’????’.

       uid=n, gid=n
              Set the owner and group of all files.  (Default: the uid and gid of the current process.)

       dir_umask=n, file_umask=n, umask=n
              Set  the umask used for all directories, all regular files, or all files and directories.  Defaults to
              the umask of the current process.

       session=n
              Select the CDROM session to mount.  Defaults to leaving that  decision  to  the  CDROM  driver.   This
              option will fail with anything but a CDROM as underlying device.

       part=n Select  partition number n from the device.  Only makes sense for CDROMS.  Defaults to not parsing the
              partition table at all.

       quiet  Don’t complain about invalid mount options.

Mount options for hpfs
       uid=value and gid=value
              Set the owner and group of all files. (Default: the uid and gid of the current process.)

       umask=value
              Set the umask (the bitmask of the permissions that are not present). The default is the umask  of  the
              current process.  The value is given in octal.

       case=lower / case=asis
              Convert all files names to lower case, or leave them.  (Default: case=lower.)

       conv=binary / conv=text / conv=auto
              For  conv=text,  delete  some random CRs (in particular, all followed by NL) when reading a file.  For
              conv=auto, choose more or less at random between conv=binary and  conv=text.   For  conv=binary,  just
              read what is in the file. This is the default.

       nocheck
              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660
       ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also
       seen on some DVDs. See also the udf filesystem.)

       Normal iso9660 filenames appear in a 8.3 format (i.e., DOS-like restrictions  on  filename  length),  and  in
       addition  all characters are in upper case.  Also there is no field for file ownership, protection, number of
       links, provision for block/character devices, etc.

       Rock Ridge is an extension to iso9660 that provides all of these unix like  features.   Basically  there  are
       extensions  to each directory record that supply all of the additional information, and when Rock Ridge is in
       use, the filesystem is indistinguishable from a normal UNIX file system (except  that  it  is  read-only,  of
       course).

       norock Disable the use of Rock Ridge extensions, even if available. Cf. map.

       nojoliet
              Disable the use of Microsoft Joliet extensions, even if available. Cf. map.

       check=r[elaxed] / check=s[trict]
              With  check=relaxed,  a  filename  is  first converted to lower case before doing the lookup.  This is
              probably only meaningful together with norock and map=normal.  (Default: check=strict.)

       uid=value and gid=value
              Give all files in the file system the indicated user or group id, possibly overriding the  information
              found in the Rock Ridge extensions.  (Default: uid=0,gid=0.)

       map=n[ormal] / map=o[ff] / map=a[corn]
              For  non-Rock  Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing
              ‘;1’, and converts ‘;’ to ‘.’.  With map=off no name  translation  is  done.  See  norock.   (Default:
              map=normal.)  map=acorn is like map=normal but also apply Acorn extensions if present.

       mode=value
              For  non-Rock  Ridge volumes, give all files the indicated mode.  (Default: read permission for every-
              body.)  Since Linux 2.1.37 one no longer needs to specify the mode in decimal. (Octal is indicated  by
              a leading 0.)

       unhide Also show hidden and associated files.  (If the ordinary files and the associated or hidden files have
              the same filenames, this may make the ordinary files inaccessible.)

       block=[512|1024|2048]
              Set the block size to the indicated value.  (Default: block=1024.)

       conv=a[uto] / conv=b[inary] / conv=m[text] / conv=t[ext]
              (Default: conv=binary.)  Since Linux 1.3.54 this option has no effect anymore.  (And  non-binary  set-
              tings used to be very dangerous, possibly leading to silent data corruption.)

       cruft  If  the  high byte of the file length contains other garbage, set this mount option to ignore the high
              order bits of the file length.  This implies that a file cannot be larger than 16MB.

       session=x
              Select number of session on multisession CD. (Since 2.3.4.)

       sbsector=xxx
              Session begins from sector xxx. (Since 2.3.4.)

       The following options are the same as for vfat and specifying them only makes sense when using discs  encoded
       using Microsoft’s Joliet extensions.

       iocharset=value
              Character  set  to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default
              is iso8859-1.

       utf8   Convert 16 bit Unicode characters on CD to UTF-8.

Mount options for jfs
       iocharset=name
              Character set to use for converting from Unicode to ASCII.  The default is to do no  conversion.   Use
              iocharset=utf8  for  UTF8 translations.  This requires CONFIG_NLS_UTF8 to be set in the kernel .config
              file.

       resize=value
              Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it.  This  option
              is  only  valid  during  a  remount, when the volume is mounted read-write. The resize keyword with no
              value will grow the volume to the full size of the partition.

       nointegrity
              Do not write to the journal.  The primary use of this option is to allow for higher  performance  when
              restoring  a  volume  from  backup  media. The integrity of the volume is not guaranteed if the system
              abnormally abends.

       integrity
              Default.  Commit metadata changes to the journal.  Use this option to remount a volume where the noin-
              tegrity option was previously specified in order to restore normal behavior.

       errors=continue / errors=remount-ro / errors=panic
              Define  the behaviour when an error is encountered.  (Either ignore errors and just mark the file sys-
              tem erroneous and continue, or remount the file system read-only, or panic and halt the system.)

       noquota / quota / usrquota / grpquota
              These options are accepted but ignored.

Mount options for minix
       None.

Mount options for msdos
       See mount options for fat.  If the msdos file system detects an inconsistency, it reports an error  and  sets
       the file system read-only. The file system can be made writeable again by remounting it.

Mount options for ncpfs
       Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount sys-
       tem call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does  not  know
       anything about ncpfs.

Mount options for nfs
       Instead  of  a  textual option string, parsed by the kernel, the nfs file system expects a binary argument of
       type struct nfs_mount_data.  The program mount itself parses the following options of the  form  ‘tag=value’,
       and  puts  them  in  the  structure  mentioned: rsize=n, wsize=n, timeo=n, retrans=n, acregmin=n, acregmax=n,
       acdirmin=n, acdirmax=n, actimeo=n, retry=n, port=n, mountport=n,  mounthost=name,  mountprog=n,  mountvers=n,
       nfsprog=n,  nfsvers=n,  namlen=n.   The  option  addr=n  is accepted but ignored.  Also the following Boolean
       options, possibly preceded by no are recognized: bg, fg, soft, hard, intr, posix, cto, ac,  tcp,  udp,  lock.
       For details, see nfs(5).

       Especially useful options include

       rsize=32768,wsize=32768
              This causes the NFS client to try to negotiate a buffer size up to the size specified.  A large buffer
              size does improve performance, but both the server and client have to support it.  In the  case  where
              one  of  these  does not support the size specified, the size negotiated will be the largest that both
              support.

       intr   This will allow NFS operations (on hard mounts) to be interrupted while waiting for  a  response  from
              the server.

       nolock Do not use locking. Do not start lockd.

Mount options for nfs4
       Instead  of  a textual option string, parsed by the kernel, the nfs4 file system expects a binary argument of
       type struct nfs4_mount_data.  The program mount itself parses the following options of the form  ‘tag=value’,
       and  puts  them  in  the  structure  mentioned: rsize=n, wsize=n, timeo=n, retrans=n, acregmin=n, acregmax=n,
       acdirmin=n, acdirmax=n, actimeo=n, retry=n, port=n, proto=n,  clientaddr=n,  sec=n.   The  option  addr=n  is
       accepted  but  ignored.   Also the following Boolean options, possibly preceded by no are recognized: bg, fg,
       soft, hard, intr, cto, ac, For details, see nfs(5).

       Especially useful options include

       rsize=32768,wsize=32768
              This causes the NFS4 client to try to negotiate a buffer size up  to  the  size  specified.   A  large
              buffer  size does improve performance, but both the server and client have to support it.  In the case
              where one of these does not support the size specified, the size negotiated will be the  largest  that
              both support.

       intr   This  will  allow NFS4 operations (on hard mounts) to be interrupted while waiting for a response from
              the server.

Mount options for ntfs
       iocharset=name
              Character set to use when returning file names.  Unlike  VFAT,  NTFS  suppresses  names  that  contain
              unconvertible characters. Deprecated.

       nls=name
              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

       uni_xlate=[0|1|2]
              For  0  (or  ‘no’  or ‘false’), do not use escape sequences for unknown Unicode characters.  For 1 (or
              ‘yes’ or ‘true’) or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 give a little-
              endian encoding and 1 a byteswapped bigendian encoding.

       posix=[0|1]
              If  enabled (posix=1), the file system distinguishes between upper and lower case. The 8.3 alias names
              are presented as hard links instead of being suppressed.

       uid=value, gid=value and umask=value
              Set the file permission on the filesystem.  The umask value is given in octal.  By default, the  files
              are owned by root and not readable by somebody else.

Mount options for proc
       uid=value and gid=value
              These options are recognized, but have no effect as far as I can see.

Mount options for ramfs
       Ramfs  is a memory based filesystem. Mount it and you have it. Unmount it and it is gone. Present since Linux
       2.3.99pre4.  There are no mount options.

Mount options for reiserfs
       Reiserfs  is  a  journaling  filesystem.   The  reiserfs  mount  options  are   more   fully   described   at
       http://www.namesys.com/mount-options.html.

       conv   Instructs  version  3.6 reiserfs software to mount a version 3.5 file system, using the 3.6 format for
              newly created objects. This file system will no longer be compatible with reiserfs 3.5 tools.

       hash=rupasov / hash=tea / hash=r5 / hash=detect
              Choose which hash function reiserfs will use to find files within directories.

              rupasov
                     A hash invented by Yury Yu. Rupasov.  It is fast and preserves locality, mapping  lexicographi-
                     cally  close  file  names to close hash values.  This option should not be used, as it causes a
                     high probability of hash collisions.

              tea    A Davis-Meyer function implemented by Jeremy Fitzhardinge.  It uses hash permuting bits in  the
                     name.   It  gets high randomness and, therefore, low probability of hash collisions at some CPU
                     cost.  This may be used if EHASHCOLLISION errors are experienced with the r5 hash.

              r5     A modified version of the rupasov hash. It is used by default and is the best choice unless the
                     file system has huge directories and unusual file-name patterns.

              detect Instructs  mount  to  detect  which  hash function is in use by examining the file system being
                     mounted,  and to write this information into the reiserfs superblock. This is  only  useful  on
                     the first mount of an old format file system.

       hashed_relocation
              Tunes the block allocator. This may provide performance improvements in some situations.

       no_unhashed_relocation
              Tunes the block allocator. This may provide performance improvements in some situations.

       noborder
              Disable  the  border  allocator  algorithm invented by Yury Yu. Rupasov.  This may provide performance
              improvements in some situations.

       nolog  Disable journalling. This will provide slight performance improvements in some situations at the  cost
              of losing reiserfs’s fast recovery from crashes.  Even with this option turned on, reiserfs still per-
              forms all journalling operations, save for actual writes into its journalling area.  Implementation of
              nolog is a work in progress.

       notail By  default,  reiserfs  stores small files and ‘file tails’ directly into its tree. This confuses some
              utilities such as LILO(8).  This option is used to disable packing of files into the tree.

       replayonly
              Replay the transactions which are in the journal, but do not actually mount the  file  system.  Mainly
              used by reiserfsck.

       resize=number
              A  remount option which permits online expansion of reiserfs partitions.  Instructs reiserfs to assume
              that the device has number blocks.  This option is designed for use with devices which are under logi-
              cal  volume  management  (LVM).   There  is  a  special  resizer  utility  which  can be obtained from
              ftp://ftp.namesys.com/pub/reiserfsprogs.

Mount options for romfs
       None.

Mount options for smbfs
       Just like nfs, the smbfs implementation expects a binary argument (a struct smb_mount_data) to the mount sys-
       tem  call.  This argument is constructed by smbmount(8) and the current version of mount (2.12) does not know
       anything about smbfs.

Mount options for sysv
       None.

Mount options for tmpfs
       The following parameters accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and  giga)  and  can  be
       changed on remount.

       size=nbytes
              Override  default  maximum  size  of  the filesystem.  The size is given in bytes, and rounded down to
              entire pages.  The default is half of the memory.

       nr_blocks=
              Set number of blocks.

       nr_inodes=
              Set number of inodes.

       mode=  Set initial permissions of the root directory.

Mount options for udf
       udf is the "Universal Disk Format" filesystem defined by the Optical Storage Technology Association,  and  is
       often used for DVD-ROM.  See also iso9660.

       gid=   Set the default group.

       umask= Set the default umask.  The value is given in octal.

       uid=   Set the default user.

       unhide Show otherwise hidden files.

       undelete
              Show deleted files in lists.

       nostrict
              Unset strict conformance.

       iocharset
              Set the NLS character set.

       bs=    Set the block size. (May not work unless 2048.)

       novrs  Skip volume sequence recognition.

       session=
              Set the CDROM session counting from 0. Default: last session.

       anchor=
              Override standard anchor location. Default: 256.

       volume=
              Override the VolumeDesc location. (unused)

       partition=
              Override the PartitionDesc location. (unused)

       lastblock=
              Set the last block of the filesystem.

       fileset=
              Override the fileset block location. (unused)

       rootdir=
              Override the root directory location. (unused)

Mount options for ufs
       ufstype=value
              UFS  is  a  file system widely used in different operating systems.  The problem are differences among
              implementations. Features of some implementations are undocumented, so its hard to recognize the  type
              of  ufs  automatically.   That’s  why the user must specify the type of ufs by mount option.  Possible
              values are:

              old    Old format of ufs, this is the default, read only.  (Don’t forget to give the -r option.)

              44bsd  For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

              hp     For filesystems created by HP-UX, read-only.

              nextstep
                     For filesystems created by NeXTStep (on NeXT station) (currently read only).

              nextstep-cd
                     For NextStep CDROMs (block_size == 2048), read-only.

              openstep
                     For filesystems created by OpenStep (currently read only).  The same filesystem  type  is  also
                     used by Mac OS X.

       onerror=value
              Set behaviour on error:

              panic  If an error is encountered, cause a kernel panic.

              [lock|umount|repair]
                     These  mount  options don’t do anything at present; when an error is encountered only a console
                     message is printed.

Mount options for umsdos
       See mount options for msdos.  The dotsOK option is explicitly killed by umsdos.

Mount options for vfat
       First of all, the mount options for fat are recognized.  The dotsOK option  is  explicitly  killed  by  vfat.
       Furthermore, there are

       uni_xlate
              Translate unhandled Unicode characters to special escaped sequences.  This lets you backup and restore
              filenames that are created with any Unicode characters. Without this option, a ’?’  is  used  when  no
              translation  is  possible.  The  escape  character  is ’:’ because it is otherwise illegal on the vfat
              filesystem. The escape sequence that gets used, where u is the unicode character, is: ’:’, (u & 0x3f),
              ((u>>6) & 0x3f), (u>>12).

       posix  Allow two files with names that only differ in case.

       nonumtail
              First try to make a short name without sequence number, before trying name~num.ext.

       utf8   UTF8  is  the  filesystem  safe  8-bit  encoding  of Unicode that is used by the console. It can be be
              enabled for the filesystem with this option.  If ‘uni_xlate’ gets set, UTF8 gets disabled.

       shortname=[lower|win95|winnt|mixed]

              Defines the behaviour for creation and display of filenames which fit into 8.3 characters. If  a  long
              name for a file exists, it will always be preferred display. There are four modes:

              lower  Force  the  short name to lower case upon display; store a long name when the short name is not
                     all upper case.

              win95  Force the short name to upper case upon display; store a long name when the short name  is  not
                     all upper case.

              winnt  Display the shortname as is; store a long name when the short name is not all lower case or all
                     upper case.

              mixed  Display the short name as is; store a long name when the short name is not all upper case.

       The default is "lower".

Mount options for usbfs
       devuid=uid and devgid=gid and devmode=mode
              Set the owner and group and mode of the device files in the usbfs  file  system  (default:  uid=gid=0,
              mode=0644). The mode is given in octal.

       busuid=uid and busgid=gid and busmode=mode
              Set  the owner and group and mode of the bus directories in the usbfs file system (default: uid=gid=0,
              mode=0555). The mode is given in octal.

       listuid=uid and listgid=gid and listmode=mode
              Set the owner and group and mode of the file devices (default:  uid=gid=0,  mode=0444).  The  mode  is
              given in octal.

Mount options for xenix
       None.

Mount options for xfs
       biosize=size
              Sets  the  preferred buffered I/O size (default size is 64K).  size must be expressed as the logarithm
              (base2) of the desired I/O size.  Valid values for this option are 14 through 16, inclusive (i.e. 16K,
              32K,  and  64K  bytes).  On machines with a 4K pagesize, 13 (8K bytes) is also a valid size.  The pre-
              ferred buffered I/O size can also be altered on an individual file basis  using  the  ioctl(2)  system
              call.

       dmapi  /  xdsm
              Enable the DMAPI (Data Management API) event callouts.

       logbufs=value
              Set  the  number of in-memory log buffers.  Valid numbers range from 2-8 inclusive.  The default value
              is 8 buffers for filesystems with a blocksize of 64K, 4 buffers for filesystems with  a  blocksize  of
              32K,  3  buffers  for filesystems with a blocksize of 16K, and 2 buffers for all other configurations.
              Increasing the number of buffers may increase performance on some workloads at the cost of the  memory
              used for the additional log buffers and their associated control structures.

       logbsize=value
              Set  the size of each in-memory log buffer.  Valid sizes are 16384 (16K) and 32768 (32K).  The default
              value for machines with more than 32MB of memory is 32768, machines with  less  memory  use  16384  by
              default.

       logdev=device and rtdev=device
              Use  an  external  log  (metadata journal) and/or real-time device.  An XFS filesystem has up to three
              parts: a data section, a log section, and a real-time section.  The real-time section is optional, and
              the log section can be separate from the data section or contained within it.  Refer to xfs(5).

       noalign
              Data allocations will not be aligned at stripe unit boundaries.

       noatime
              Access timestamps are not updated when a file is read.

       norecovery
              The  filesystem  will  be  mounted  without  running  log recovery.  If the filesystem was not cleanly
              unmounted, it is likely to be inconsistent when mounted in norecovery mode.  Some files or directories
              may  not  be  accessible because of this.  Filesystems mounted norecovery must be mounted read-only or
              the mount will fail.

       nouuid Ignore the filesystem uuid. This avoids errors for duplicate uuids.

       osyncisdsync
              Make writes to files opened with the O_SYNC flag set behave as if  the  O_DSYNC  flag  had  been  used
              instead.   This  can  result  in better performance without compromising data safety.  However if this
              option is in effect, timestamp updates from O_SYNC writes can be lost if the system crashes.

       quota / usrquota / uqnoenforce
              User disk quota accounting enabled, and limits (optionally) enforced.

       grpquota / gqnoenforce
              Group disk quota accounting enabled and limits (optionally) enforced.

       sunit=value and swidth=value
              Used to specify the stripe unit and width for a RAID device or a stripe volume.  value must be  speci-
              fied in 512-byte block units.  If this option is not specified and the filesystem was made on a stripe
              volume or the stripe width or unit were specified for the RAID device at mkfs  time,  then  the  mount
              system  call  will  restore  the value from the superblock.  For filesystems that are made directly on
              RAID devices, these options can be used to override the information in the superblock if the  underly-
              ing  disk  layout changes after the filesystem has been created.  The swidth option is required if the
              sunit option has been specified, and must be a multiple of the sunit value.

Mount options for xiafs
       None. Although nothing is wrong with xiafs, it is  not  used  much,  and  is  not  maintained.  Probably  one
       shouldn’t use it.  Since Linux version 2.1.21 xiafs is no longer part of the kernel source.

THE LOOP DEVICE
       One further possible type is a mount via the loop device. For example, the command

         mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024

       will  set up the loop device /dev/loop3 to correspond to the file /tmp/fdimage, and then mount this device on
       /mnt.

       This type of mount knows about three options, namely loop, offset and encryption, that are really options  to
       losetup(8).  (These options can be used in addition to those specific to the filesystem type.)

       If  no explicit loop device is mentioned (but just an option ‘-o loop’ is given), then mount will try to find
       some unused loop device and use that.  If you are not so unwise as to  make  /etc/mtab  a  symbolic  link  to
       /proc/mounts  then  any  loop  device  allocated  by mount will be freed by umount.  You can also free a loop
       device by hand, using ‘losetup -d’, see losetup(8).

RETURN CODES
       mount has the following return codes (the bits can be ORed):

       0      success

       1      incorrect invocation or permissions

       2      system error (out of memory, cannot fork, no more loop devices)

       4      internal mount bug or missing nfs support in mount

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

FILES
       /etc/fstab        file system table

       /etc/mtab         table of mounted file systems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

SEE ALSO
       mount(2), umount(2), fstab(5), umount(8), swapon(8), nfs(5),  xfs(5),  e2label(8),  xfs_admin(8),  mountd(8),
       nfsd(8), mke2fs(8), tune2fs(8), losetup(8)

BUGS
       It is possible for a corrupted file system to cause a crash.

       Some  Linux  file  systems don’t support -o sync and -o dirsync (the ext2, ext3, fat and vfat file systems do
       support synchronous updates (a la BSD) when mounted with the sync option).

       The -o remount may not be able to change mount parameters (all ext2fs-specific  parameters,  except  sb,  are
       changeable with a remount, for example, but you can’t change gid or umask for the fatfs).

       Mount by label or uuid will work only if your devices have the names listed in /proc/partitions.  In particu-
       lar, it may well fail if the kernel was compiled with devfs but devfs is not mounted.

       It is possible that files /etc/mtab and /proc/mounts don’t match. The first file is based only on  the  mount
       command  options,  but  the  content  of the second file also depends on the kernel and others settings (e.g.
       remote NFS server. In particular case the mount command may reports unreliable information about a NFS  mount
       point and the /proc/mounts file usually contains more reliable information.)

       Checking  files  on NFS filesystem referenced by file descriptors (i.e. the fcntl and ioctl families of func-
       tions) may lead to inconsistent result due to the lack of consistency check in kernel even if noac is used.

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

Linux 2.6                         2004-12-16                          MOUNT(8)