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 main-
       tain this file.  The order of records in  fstab  is  important  because
       fsck(8), mount(8), and umount(8) sequentially iterate through fstab do-
       ing 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 filesys-
              tem 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 parti-
              tions 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 representa-
              tion of the UUID should be based on lower case characters.

       The second field (fs_file).
              This  field  describes the mount point (target) for the filesys-
              tem.  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 `\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, hfs-
              plus, 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 swap-
              ping, 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.   It  con-
              tains at least the type of mount (ro or rw), plus any additional
              options appropriate to the filesystem  type  (including  perfor-
              mance-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 ex-
                     ist.

       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 avail-
              able 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 getmn-
       tent(3) or libmount.

       The keyword ignore as a filesystem type (3rd field) is no  longer  sup-
       ported  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)