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 writ-
       ten; 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 com-
       ments.  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'  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 `40' and '11' 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  depre-
              cated).

       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.

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).

FILES

       /etc/fstab, <fstab.h>

SEE ALSO

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

HISTORY

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

AVAILABILITY

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

util-linux                                                         February 2015                                                          FSTAB(5)