sys-utils/fstab.5

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  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 or
  72 remote filesystem to be mounted.
  73 .LP
  74 For ordinary mounts, it will hold (a link to) a block special
  75 device node (as created by
  76 .BR mknod (8))
  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 these can be escaped as `\\040'.
 120 .RE
 121
 122 .B The third field
 123 .RI ( fs_vfstype ).
 124 .RS
 125 This field describes the type of the filesystem.  Linux supports many
 126 filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus,
 127 tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more.
 128 For more details, see
 129 .BR mount (8).
 130
 131 An entry
 132 .I swap
 133 denotes a file or partition to be used
 134 for swapping, cf.\&
 135 .BR swapon (8).
 136 An entry
 137 .I none
 138 is useful for bind or move mounts.
 139
 140 More than one type may be specified in a comma-separated list.
 141
 142 .BR mount (8)
 143 and
 144 .BR umount (8)
 145 support filesystem
 146 .IR subtypes .
 147 The subtype is defined by '.subtype' suffix.  For
 148 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
 149 any prefix to the first fstab field (for example 'sshfs#example.com' is
 150 deprecated).
 151 .RE
 152
 153 .B The fourth field
 154 .RI ( fs_mntops ).
 155 .RS
 156 This field describes the mount options associated with the filesystem.
 157
 158 It is formatted as a comma-separated list of options.
 159 It contains at least the type of mount
 160 .RB ( ro
 161 or
 162 .BR rw ),
 163 plus any additional options appropriate to the filesystem
 164 type (including performance-tuning options).
 165 For details, see
 166 .BR mount (8)
 167 or
 168 .BR swapon (8).
 169
 170 Basic filesystem-independent options are:
 171 .TP
 172 .B defaults
 173 use default options: rw, suid, dev, exec, auto, nouser, and async.
 174 .TP
 175 .B noauto
 176 do not mount when "mount -a" is given (e.g., at boot time)
 177 .TP
 178 .B user
 179 allow a user to mount
 180 .TP
 181 .B owner
 182 allow device owner to mount
 183 .TP
 184 .B comment
 185 or
 186 .B x-<name>
 187 for use by fstab-maintaining programs
 188 .TP
 189 .B nofail
 190 do not report errors for this device if it does not exist.
 191 .RE
 192
 193 .B The fifth field
 194 .RI ( fs_freq ).
 195 .RS
 196 This field is used by
 197 .BR dump (8)
 198 to determine which filesystems need to be dumped.
 199 Defaults to zero (don't dump) if not present.
 200 .RE
 201
 202 .B The sixth field
 203 .RI ( fs_passno ).
 204 .RS
 205 This field is used by
 206 .BR fsck (8)
 207 to determine the order in which filesystem checks are done at
 208 boot time.  The root filesystem should be specified with a
 209 .I fs_passno
 210 of 1.  Other filesystems should have a
 211 .I fs_passno
 212 of 2.  Filesystems within a drive will be checked sequentially, but
 213 filesystems on different drives will be checked at the same time to utilize
 214 parallelism available in the hardware.
 215 Defaults to zero (don't fsck) if not present.
 216
 217 .SH NOTES
 218 The proper way to read records from
 219 .B fstab
 220 is to use the routines
 221 .BR getmntent (3)
 222 or
 223 .BR libmount .
 224
 225 The keyword
 226 .B ignore
 227 as a filesystem type (3rd field) is no longer supported by the pure
 228 libmount based mount utility (since util-linux v2.22).
 229
 230 .SH FILES
 231 .IR /etc/fstab ,
 232 .I <fstab.h>
 233 .SH "SEE ALSO"
 234 .BR getmntent (3),
 235 .BR fs (5),
 236 .BR findmnt (8),
 237 .BR mount (8),
 238 .BR swapon (8)
 239 .SH HISTORY
 240 The ancestor of this
 241 .B fstab
 242 file format appeared in 4.0BSD.
 243 .\" But without comment convention, and options and vfs_type.
 244 .\" Instead there was a type rw/ro/rq/sw/xx, where xx is the present 'ignore'.
 245 .SH AVAILABILITY
 246 This man page is part of the util-linux package and is available from
 247 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.