1FSTAB(5) File formats FSTAB(5)
2
6 fstab - static information about the filesystems
7
9 /etc/fstab
10
12 The file fstab contains descriptive information about the filesystems
13 the system can mount. fstab is only read by programs, and not written;
14 it is the duty of the system administrator to properly create and
15 maintain this file. The order of records in fstab is important because
16 fsck(8), mount(8), and umount(8) sequentially iterate through fstab
17 doing their thing.
18 Each filesystem is described on a separate line. Fields on each line
20 are separated by tabs or spaces. Lines starting with '#' are comments.
21 Blank lines are ignored.
22 The following is a typical example of an fstab entry:
24 LABEL=t-home2 /home ext4 defaults,auto_da_alloc 0 2
26 The first field (fs_spec).
28 This field describes the block special device, remote filesystem or
29 filesystem image for loop device to be mounted or swap file or swap
30 device to be enabled.
31 For ordinary mounts, it will hold (a link to) a block special device
33 node (as created by mknod(2)) for the device to be mounted, like
34 /dev/cdrom or /dev/sdb7. For NFS mounts, this field is <host>:<dir>,
35 e.g., knuth.aeb.nl:/. For filesystems with no storage, any string can
36 be used, and will show up in df(1) output, for example. Typical usage
37 is proc for procfs; mem, none, or tmpfs for tmpfs. Other special
38 filesystems, like udev and sysfs, are typically not listed in fstab.
39 LABEL=<label> or UUID=<uuid> may be given instead of a device name.
41 This is the recommended method, as device names are often a coincidence
42 of hardware detection order, and can change when other disks are added
43 or removed. For example, 'LABEL=Boot' or
44 'UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'. (Use a filesystem-specific
45 tool like e2label(8), xfs_admin(8), or fatlabel(8) to set LABELs on
46 filesystems).
47 It’s also possible to use PARTUUID= and PARTLABEL=. These partitions
49 identifiers are supported for example for GUID Partition Table (GPT).
50 See mount(8), blkid(8) or lsblk(8) for more details about device
52 identifiers.
53 Note that mount(8) uses UUIDs as strings. The string representation of
55 the UUID should be based on lower case characters. But when specifying
56 the volume ID of FAT or NTFS file systems upper case characters are
57 used (e.g UUID="A40D-85E7" or UUID="61DB7756DB7779B3").
58 The second field (fs_file).
60 This field describes the mount point (target) for the filesystem. For
61 swap area, this field should be specified as `none'. If the name of the
62 mount point contains spaces or tabs these can be escaped as `\040' and
63 '\011' respectively.
64 The third field (fs_vfstype).
66 This field describes the type of the filesystem. Linux supports many
67 filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus, tmpfs,
68 sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more. For more
69 details, see mount(8).
70 An entry swap denotes a file or partition to be used for swapping, cf.
72 swapon(8). An entry none is useful for bind or move mounts.
73 More than one type may be specified in a comma-separated list.
75 mount(8) and umount(8) support filesystem subtypes. The subtype is
77 defined by '.subtype' suffix. For example 'fuse.sshfs'. It’s
78 recommended to use subtype notation rather than add any prefix to the
79 first fstab field (for example 'sshfs#example.com' is deprecated).
80 The fourth field (fs_mntops).
82 This field describes the mount options associated with the filesystem.
83 It is formatted as a comma-separated list of options and is optional
85 for mount(8) or swapon(8). The usual convention is to use at least
86 "defaults" keyword there.
87 It usually contains the type of mount (ro or rw, the default is rw),
89 plus any additional options appropriate to the filesystem type
90 (including performance-tuning options). For details, see mount(8) or
91 swapon(8).
92 Basic filesystem-independent options are:
94 defaults
96 use default options. The default depends on the kernel and the
97 filesystem. mount(8) does not have any hardcoded set of default
98 options. The kernel default is usually rw, suid, dev, exec, auto,
99 nouser, and async.
100 noauto
102 do not mount when mount -a is given (e.g., at boot time)
103 user
105 allow a user to mount
106 owner
108 allow device owner to mount
109 comment
111 or x-<name> for use by fstab-maintaining programs
112 nofail
114 do not report errors for this device if it does not exist.
115 The fifth field (fs_freq).
117 This field is used by dump(8) to determine which filesystems need to be
118 dumped. Defaults to zero (don’t dump) if not present.
119 The sixth field (fs_passno).
121 This field is used by fsck(8) to determine the order in which
122 filesystem checks are done at boot time. The root filesystem should be
123 specified with a fs_passno of 1. Other filesystems should have a
124 fs_passno of 2. Filesystems within a drive will be checked
125 sequentially, but filesystems on different drives will be checked at
126 the same time to utilize parallelism available in the hardware.
127 Defaults to zero (don’t check the filesystem) if not present.
128
130 /etc/fstab, <fstab.h>
131
133 The proper way to read records from fstab is to use the routines
134 getmntent(3) or libmount.
135 The keyword ignore as a filesystem type (3rd field) is no longer
137 supported by the pure libmount based mount utility (since util-linux
138 v2.22).
139
141 The ancestor of this fstab file format appeared in 4.0BSD.
142
144 getmntent(3), fs(5), findmnt(8), mount(8), swapon(8)
145
147 For bug reports, use the issue tracker at
148 https://github.com/util-linux/util-linux/issues.
149
151 fstab is part of the util-linux package which can be downloaded from
152 Linux Kernel Archive
153 <https://www.kernel.org/pub/linux/utils/util-linux/>.
154util-linux 2.39.2 2023-08-17 FSTAB(5)