fstab

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.

       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 or remote filesystem to be mounted.

              For ordinary mounts, it will hold (a link to) a block special device node (as  cre‐
              ated  by  mknod(8)) for the device to be mounted, like `/dev/cdrom' or `/dev/sdb7'.
              For NFS mounts, this field is :, e.g., `knuth.aeb.nl:/'.   For  filesys‐
              tems 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=  or  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 for the filesystem.  For swap partitions, this
              field should be specified as `none'. If the name of the mount point contains spaces
              these can be escaped as `\040'.

       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 nota‐
              tion  rather than add any prefix to the first fstab field (for example 'sshfs#exam‐
              ple.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.  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- 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, 

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

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  ftp://ftp.ker‐
       nel.org/pub/linux/utils/util-linux/.

util-linux                                February 2015                                  FSTAB(5)
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