Section (5) fstab

Linux manual pages Section 5  


fstab — static information about the filesystems


.I /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.

Each filesystem is described on a separate line. Fields on each line are separated by tabs or spaces. Lines starting with _zsingle_quotesz_#_zsingle_quotesz_ 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 or remote filesystem to be mounted.

For ordinary mounts, it will hold (a link to) a block special device node (as created by mknod(8)) for the device to be mounted, like `/dev/cdrom_zsingle_quotesz_ or `/dev/sdb7_zsingle_quotesz_. For NFS mounts, this field is <host>:<dir>, e.g., ` For filesystems with no storage, any string can be used, and will show up in df(1) output, for example. Typical usage is `proc_zsingle_quotesz_ for procfs; `mem_zsingle_quotesz_, `none_zsingle_quotesz_, or `tmpfs_zsingle_quotesz_ 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_zsingle_quotesz_ or `UUID=3e6be9de-8139-11d1-9106-a43f08d823a6_zsingle_quotesz_. (Use a filesystem-specific tool like e2label(8), xfs_admin(8), or fatlabel(8) to set LABELs on filesystems).

It_zsingle_quotesz_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_zsingle_quotesz_. If the name of the mount point contains spaces or tabs these can be escaped as `40_zsingle_quotesz_ and _zsingle_quotesz_11_zsingle_quotesz_ 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 _zsingle_quotesz_.subtype_zsingle_quotesz_ suffix. For example _zsingle_quotesz_fuse.sshfs_zsingle_quotesz_. It_zsingle_quotesz_s recommended to use subtype notation rather than add any prefix to the first fstab field (for example _zsingle_quotesz_sshfs#example.com_zsingle_quotesz_ 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:


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


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


allow a user to mount


allow device owner to mount


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


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_zsingle_quotesz_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_zsingle_quotesz_t fsck) if not present.


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).


/etc/fstab, <fstab.h>


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


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


This man page is part of the util-linux package and is available from

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    (#)fstab.5 6.5 (Berkeley) 5/10/91