FSTAB(5)                         File formats                         FSTAB(5)

NAME
       fstab - static information about the filesystems

SYNOPSIS
       /etc/fstab

DESCRIPTION
       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.

       The file is not read by mount(8) only but often is used by many other
       tools and daemons, and proper functionality may require additional
       steps. For example, on systemd-based systems, it's recommended to use
       systemctl daemon-reload after fstab modification.

       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
       device 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. But when specifying
       the volume ID of FAT or NTFS file systems upper case characters are
       used (e.g UUID="A40D-85E7" or UUID="61DB7756DB7779B3").

   The second field (fs_file).
       This field describes the mount point (target) for the filesystem. For
       swap area, 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 and is optional
       for mount(8) or swapon(8). The usual convention is to use at least
       "defaults" keyword there.

       It usually contains the type of mount (ro or rw, the default is 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. The default depends on the kernel and the
           filesystem. mount(8) does not have any hardcoded set of default
           options. The kernel default is usually 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 check the filesystem) if not present.

FILES
       /etc/fstab, <fstab.h>

NOTES
       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).

       This document describes handling of fstab by util-linux and libmount.
       For systemd, read systemd documentation. There are slight differences.

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

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

REPORTING BUGS
       For bug reports, use the issue tracker at
       <https://github.com/util-linux/util-linux/issues>.

AVAILABILITY
       fstab is part of the util-linux package which can be downloaded from
       Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.40                   2024-04-06                          FSTAB(5)