fstab(5) — Linux manual page


FSTAB(5)                        File Formats                        FSTAB(5)

NAME         top

       fstab - static information about the filesystems

SYNOPSIS         top


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

       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'

       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

              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:

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

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

              user   allow a user to mount

              owner  allow device owner to mount

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

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

       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

       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

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

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
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-12.)  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

util-linux                      February 2015                       FSTAB(5)

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