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NAME | SYNOPSIS | DESCRIPTION | FILES | NOTES | HISTORY | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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FSTAB(5) File formats FSTAB(5)
fstab - static information about the filesystems
/etc/fstab
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, with fields
separated by tabs or spaces. The line is split into fields before
being parsed. This means that any spaces or tabs within the fields
must be escaped using \040 or \011, even within quoted strings
(e.g. LABEL="foo\040bar").
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.
/etc/fstab, <fstab.h>
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.
The ancestor of this fstab file format appeared in 4.0BSD.
getmntent(3), fs(5), findmnt(8), mount(8), swapon(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
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/>. 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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) 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 [email protected]
util-linux 2.42-start-521-ec46 2025-08-09 FSTAB(5)
Pages that refer to this page: quota(1), systemd-dissect(1), getfsent(3), getmntent(3), crypttab(5), integritytab(5), lxc.container.conf(5), nfs(5), proc_pid_mounts(5), repart.d(5), systemd.automount(5), systemd.mount(5), systemd.swap(5), veritytab(5), bootparam(7), kernel-command-line(7), spufs(7), systemd.generator(7), e2mmpstatus(8), findmnt(8), fsck(8@@e2fsprogs), fsck(8), fsck.btrfs(8), fsck.xfs(8), mount(8), quotacheck(8), quotaon(8), swapon(8), systemd-fstab-generator(8), systemd-gpt-auto-generator(8), systemd-hibernate-resume-generator(8), [email protected](8), systemd-remount-fs.service(8), systemd-repart(8), xfs_fsr(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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