fstab(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | FILES | NOTES | HISTORY | SEE ALSO | AVAILABILITY | COLOPHON

FSTAB(5)                      File Formats                      FSTAB(5)

NAME         top

       fstab - static information about the filesystems

SYNOPSIS         top

       /etc/fstab

DESCRIPTION         top

       The file fstab contains descriptive information about the
       filesystems the system can mount.  fstab is only read by
       programs, and not written; it is the duty of the system
       administrator to properly create and maintain this file.  The
       order of records in fstab is important because fsck(8), mount(8),
       and umount(8) sequentially iterate through fstab doing their
       thing.

       Each filesystem is described on a separate line.  Fields on each
       line are separated by tabs or spaces.  Lines starting with '#'
       are comments.  Blank lines are ignored.

       The following is a typical example of an fstab entry:

              LABEL=t-home2   /home      ext4    defaults,auto_da_alloc
              0  2

       The first field (fs_spec).
              This field describes the block special device, remote
              filesystem or filesystem image for loop device to be
              mounted or swap file or swap partition to be enabled.

              For ordinary mounts, it will hold (a link to) a block
              special device node (as created by mknod(2)) for the
              device to be mounted, like `/dev/cdrom' or `/dev/sdb7'.
              For NFS mounts, this field is <host>:<dir>, e.g.,
              `knuth.aeb.nl:/'.  For filesystems with no storage, any
              string can be used, and will show up in df(1) output, for
              example.  Typical usage is `proc' for procfs; `mem',
              `none', or `tmpfs' for tmpfs.  Other special filesystems,
              like udev and sysfs, are typically not listed in fstab.

              LABEL=<label> or UUID=<uuid> may be given instead of a
              device name.  This is the recommended method, as device
              names are often a coincidence of hardware detection order,
              and can change when other disks are added or removed.  For
              example, `LABEL=Boot' or `UUID=3e6be9de-8139-11d1-9106‐
              -a43f08d823a6'.  (Use a filesystem-specific tool like
              e2label(8), xfs_admin(8), or fatlabel(8) to set LABELs on
              filesystems).

              It's also possible to use PARTUUID= and PARTLABEL=. These
              partitions identifiers are supported for example for GUID
              Partition Table (GPT).

              See mount(8), blkid(8) or lsblk(8) for more details about
              device identifiers.

              Note that mount(8) uses UUIDs as strings. The string
              representation of the UUID should be based on lower case
              characters.

       The second field (fs_file).
              This field describes the mount point (target) for the
              filesystem.  For swap partitions, this field should be
              specified as `none'. If the name of the mount point
              contains spaces or tabs these can be escaped as `\040' and
              '\011' respectively.

       The third field (fs_vfstype).
              This field describes the type of the filesystem.  Linux
              supports many filesystem types: ext4, xfs, btrfs, f2fs,
              vfat, ntfs, hfsplus, tmpfs, sysfs, proc, iso9660, udf,
              squashfs, nfs, cifs, and many more.  For more details, see
              mount(8).

              An entry swap denotes a file or partition to be used for
              swapping, cf. swapon(8).  An entry none is useful for bind
              or move mounts.

              More than one type may be specified in a comma-separated
              list.

              mount(8) and umount(8) support filesystem subtypes.  The
              subtype is defined by '.subtype' suffix.  For example
              'fuse.sshfs'. It's recommended to use subtype notation
              rather than add any prefix to the first fstab field (for
              example 'sshfs#example.com' is deprecated).

       The fourth field (fs_mntops).
              This field describes the mount options associated with the
              filesystem.

              It is formatted as a comma-separated list of options.  It
              contains at least the type of mount (ro or rw), plus any
              additional options appropriate to the filesystem type
              (including performance-tuning options).  For details, see
              mount(8) or swapon(8).

              Basic filesystem-independent options are:

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

              noauto do not mount when "mount -a" is given (e.g., at
                     boot time)

              user   allow a user to mount

              owner  allow device owner to mount

              comment
                     or x-<name> for use by fstab-maintaining programs

              nofail do not report errors for this device if it does not
                     exist.

       The fifth field (fs_freq).
              This field is used by dump(8) to determine which
              filesystems need to be dumped.  Defaults to zero (don't
              dump) if not present.

       The sixth field (fs_passno).
              This field is used by fsck(8) to determine the order in
              which filesystem checks are done at boot time.  The root
              filesystem should be specified with a fs_passno of 1.
              Other filesystems should have a fs_passno of 2.
              Filesystems within a drive will be checked sequentially,
              but filesystems on different drives will be checked at the
              same time to utilize parallelism available in the
              hardware.  Defaults to zero (don't fsck) if not present.

FILES         top

       /etc/fstab, <fstab.h>

NOTES         top

       The proper way to read records from fstab is to use the routines
       getmntent(3) or libmount.

       The keyword ignore as a filesystem type (3rd field) is no longer
       supported by the pure libmount based mount utility (since util-
       linux v2.22).

HISTORY         top

       The ancestor of this fstab file format appeared in 4.0BSD.

SEE ALSO         top

       getmntent(3), fs(5), findmnt(8), mount(8), swapon(8)

AVAILABILITY         top

       This man page is part of the util-linux package and is available
       from https://www.kernel.org/pub/linux/utils/util-linux/.

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found
       at ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.  If you
       have a bug report for this manual page, send it to
       util-linux@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2020-12-18.  (At that time, the date of the most recent commit
       that was found in the repository was 2020-12-17.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

util-linux                    February 2015                     FSTAB(5)

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