sys-utils/fstab.5

   1 .\" Copyright (c) 1980, 1989, 1991 The Regents of the University of California.
   2 .\" All rights reserved.
   3 .\"
   4 .\" Redistribution and use in source and binary forms, with or without
   5 .\" modification, are permitted provided that the following conditions
   6 .\" are met:
   7 .\" 1. Redistributions of source code must retain the above copyright
   8 .\"    notice, this list of conditions and the following disclaimer.
   9 .\" 2. Redistributions in binary form must reproduce the above copyright
  10 .\"    notice, this list of conditions and the following disclaimer in the
  11 .\"    documentation and/or other materials provided with the distribution.
  12 .\" 3. All advertising materials mentioning features or use of this software
  13 .\"    must display the following acknowledgement:
  14 .\"     This product includes software developed by the University of
  15 .\"     California, Berkeley and its contributors.
  16 .\" 4. Neither the name of the University nor the names of its contributors
  17 .\"    may be used to endorse or promote products derived from this software
  18 .\"    without specific prior written permission.
  19 .\"
  20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30 .\" SUCH DAMAGE.
  31 .\"
  32 .\"     @(#)fstab.5     6.5 (Berkeley) 5/10/91
  33 .\"
  34 .TH FSTAB 5 "February 2015" "util-linux" "File Formats"
  35 .SH NAME
  36 fstab \- static information about the filesystems
  37 .SH SYNOPSIS
  38 .I /etc/fstab
  39 .SH DESCRIPTION
  40 The file
  41 .B fstab
  42 contains descriptive information about the filesystems the system can mount.
  43 .B fstab
  44 is only read by programs, and not written; it is the duty of the system
  45 administrator to properly create and maintain this file.  The order of records in
  46 .B fstab
  47 is important because
  48 .BR fsck (8),
  49 .BR mount (8),
  50 and
  51 .BR umount (8)
  52 sequentially iterate through
  53 .B fstab
  54 doing their thing.
  55
  56 Each filesystem is described on a separate line.
  57 Fields on each line are separated by tabs or spaces.
  58 Lines starting with '#' are comments.  Blank lines are ignored.
  59 .PP
  60 The following is a typical example of an
  61 .B fstab
  62 entry:
  63 .sp
  64 .RS 7
  65 LABEL=t-home2   /home      ext4    defaults,auto_da_alloc      0  2
  66 .RE
  67
  68 .B The first field
  69 .RI ( fs_spec ).
  70 .RS
  71 This field describes the block special device, remote filesystem or filesystem
  72 image for loop device to be mounted or swap file or swap partition to be enabled.
  73 .LP
  74 For ordinary mounts, it will hold (a link to) a block special
  75 device node (as created by
  76 .BR mknod (2))
  77 for the device to be mounted, like `/dev/cdrom' or `/dev/sdb7'.
  78 For NFS mounts, this field is <host>:<dir>, e.g., `knuth.aeb.nl:/'.
  79 For filesystems with no storage, any string can be used, and will show up in
  80 .BR df (1)
  81 output, for example.  Typical usage is `proc' for procfs; `mem', `none',
  82 or `tmpfs' for tmpfs.  Other special filesystems, like udev and sysfs,
  83 are typically not listed in
  84 .BR fstab .
  85 .LP
  86 LABEL=<label> or UUID=<uuid> may be given instead of a device name.
  87 This is the recommended method, as device names are often a coincidence
  88 of hardware detection order, and can change when other disks are added or removed.
  89 For example, `LABEL=Boot' or `UUID=3e6be9de\%-8139\%-11d1\%-9106\%-a43f08d823a6'.
  90 (Use a filesystem-specific tool like
  91 .BR e2label (8),
  92 .BR xfs_admin (8),
  93 or
  94 .BR fatlabel (8)
  95 to set LABELs on filesystems).
  96
  97 It's also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers
  98 are supported for example for GUID Partition Table (GPT).
  99
 100 See
 101 .BR mount (8),
 102 .BR blkid (8)
 103 or
 104 .BR lsblk (8)
 105 for more details about device identifiers.
 106
 107 .LP
 108 Note that
 109 .BR mount (8)
 110 uses UUIDs as strings. The string representation of the UUID should be based on
 111 lower case characters.
 112 .RE
 113
 114 .B The second field
 115 .RI ( fs_file ).
 116 .RS
 117 This field describes the mount point (target) for the filesystem.  For swap partitions, this
 118 field should be specified as `none'. If the name of the mount point
 119 contains spaces or tabs these can be escaped as `\\040' and '\\011'
 120 respectively.
 121 .RE
 122
 123 .B The third field
 124 .RI ( fs_vfstype ).
 125 .RS
 126 This field describes the type of the filesystem.  Linux supports many
 127 filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus,
 128 tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more.
 129 For more details, see
 130 .BR mount (8).
 131
 132 An entry
 133 .I swap
 134 denotes a file or partition to be used
 135 for swapping, cf.\&
 136 .BR swapon (8).
 137 An entry
 138 .I none
 139 is useful for bind or move mounts.
 140
 141 More than one type may be specified in a comma-separated list.
 142
 143 .BR mount (8)
 144 and
 145 .BR umount (8)
 146 support filesystem
 147 .IR subtypes .
 148 The subtype is defined by '.subtype' suffix.  For
 149 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
 150 any prefix to the first fstab field (for example 'sshfs#example.com' is
 151 deprecated).
 152 .RE
 153
 154 .B The fourth field
 155 .RI ( fs_mntops ).
 156 .RS
 157 This field describes the mount options associated with the filesystem.
 158
 159 It is formatted as a comma-separated list of options.
 160 It contains at least the type of mount
 161 .RB ( ro
 162 or
 163 .BR rw ),
 164 plus any additional options appropriate to the filesystem
 165 type (including performance-tuning options).
 166 For details, see
 167 .BR mount (8)
 168 or
 169 .BR swapon (8).
 170
 171 Basic filesystem-independent options are:
 172 .TP
 173 .B defaults
 174 use default options: rw, suid, dev, exec, auto, nouser, and async.
 175 .TP
 176 .B noauto
 177 do not mount when "mount \-a" is given (e.g., at boot time)
 178 .TP
 179 .B user
 180 allow a user to mount
 181 .TP
 182 .B owner
 183 allow device owner to mount
 184 .TP
 185 .B comment
 186 or
 187 .B x-<name>
 188 for use by fstab-maintaining programs
 189 .TP
 190 .B nofail
 191 do not report errors for this device if it does not exist.
 192 .RE
 193
 194 .B The fifth field
 195 .RI ( fs_freq ).
 196 .RS
 197 This field is used by
 198 .BR dump (8)
 199 to determine which filesystems need to be dumped.
 200 Defaults to zero (don't dump) if not present.
 201 .RE
 202
 203 .B The sixth field
 204 .RI ( fs_passno ).
 205 .RS
 206 This field is used by
 207 .BR fsck (8)
 208 to determine the order in which filesystem checks are done at
 209 boot time.  The root filesystem should be specified with a
 210 .I fs_passno
 211 of 1.  Other filesystems should have a
 212 .I fs_passno
 213 of 2.  Filesystems within a drive will be checked sequentially, but
 214 filesystems on different drives will be checked at the same time to utilize
 215 parallelism available in the hardware.
 216 Defaults to zero (don't fsck) if not present.
 217 .RE
 218
 219 .SH FILES
 220 .IR /etc/fstab ,
 221 .I <fstab.h>
 222
 223 .SH NOTES
 224 The proper way to read records from
 225 .B fstab
 226 is to use the routines
 227 .BR getmntent (3)
 228 or
 229 .BR libmount .
 230
 231 The keyword
 232 .B ignore
 233 as a filesystem type (3rd field) is no longer supported by the pure
 234 libmount based mount utility (since util-linux v2.22).
 235 .SH HISTORY
 236 The ancestor of this
 237 .B fstab
 238 file format appeared in 4.0BSD.
 239 .\" But without comment convention, and options and vfs_type.
 240 .SH SEE ALSO
 241 .BR getmntent (3),
 242 .BR fs (5),
 243 .BR findmnt (8),
 244 .BR mount (8),
 245 .BR swapon (8)
 246 .\" Instead there was a type rw/ro/rq/sw/xx, where xx is the present 'ignore'.
 247 .SH AVAILABILITY
 248 This man page is part of the util-linux package and is available from
 249 https://www.kernel.org/pub/linux/utils/util-linux/.