249 lines
7.3 KiB
Groff
249 lines
7.3 KiB
Groff
.\" Copyright (c) 1980, 1989, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)fstab.5 6.5 (Berkeley) 5/10/91
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.\"
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.TH FSTAB 5 "February 2015" "util-linux" "File Formats"
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.SH NAME
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fstab \- static information about the filesystems
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.SH SYNOPSIS
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.I /etc/fstab
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.SH DESCRIPTION
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The file
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.B fstab
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contains descriptive information about the filesystems the system can mount.
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.B fstab
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is only read by programs, and not written; it is the duty of the system
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administrator to properly create and maintain this file. The order of records in
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.B fstab
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is important because
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.BR fsck (8),
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.BR mount (8),
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and
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.BR umount (8)
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sequentially iterate through
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.B fstab
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doing their thing.
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Each filesystem is described on a separate line.
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Fields on each line are separated by tabs or spaces.
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Lines starting with '#' are comments. Blank lines are ignored.
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.PP
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The following is a typical example of an
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.B fstab
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entry:
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.sp
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.RS 7
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LABEL=t-home2 /home ext4 defaults,auto_da_alloc 0 2
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.RE
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.B The first field
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.RI ( fs_spec ).
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.RS
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This field describes the block special device or
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remote filesystem to be mounted.
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.LP
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For ordinary mounts, it will hold (a link to) a block special
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device node (as created by
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.BR mknod (8))
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for the device to be mounted, like `/dev/cdrom' or `/dev/sdb7'.
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For NFS mounts, this field is <host>:<dir>, e.g., `knuth.aeb.nl:/'.
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For filesystems with no storage, any string can be used, and will show up in
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.BR df (1)
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output, for example. Typical usage is `proc' for procfs; `mem', `none',
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or `tmpfs' for tmpfs. Other special filesystems, like udev and sysfs,
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are typically not listed in
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.BR fstab .
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.LP
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LABEL=<label> or UUID=<uuid> may be given instead of a device name.
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This is the recommended method, as device names are often a coincidence
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of hardware detection order, and can change when other disks are added or removed.
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For example, `LABEL=Boot' or `UUID=3e6be9de\%-8139\%-11d1\%-9106\%-a43f08d823a6'.
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(Use a filesystem-specific tool like
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.BR e2label (8),
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.BR xfs_admin (8),
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or
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.BR fatlabel (8)
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to set LABELs on filesystems).
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It's also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers
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are supported for example for GUID Partition Table (GPT).
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See
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.BR mount (8),
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.BR blkid (8)
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or
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.BR lsblk (8)
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for more details about device identifiers.
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.LP
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Note that
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.BR mount (8)
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uses UUIDs as strings. The string representation of the UUID should be based on
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lower case characters.
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.RE
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.B The second field
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.RI ( fs_file ).
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.RS
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This field describes the mount point (target) for the filesystem. For swap partitions, this
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field should be specified as `none'. If the name of the mount point
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contains spaces or tabs these can be escaped as `\\040' and '\\011'
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respectively.
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.RE
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.B The third field
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.RI ( fs_vfstype ).
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.RS
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This field describes the type of the filesystem. Linux supports many
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filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus,
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tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more.
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For more details, see
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.BR mount (8).
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An entry
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.I swap
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denotes a file or partition to be used
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for swapping, cf.\&
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.BR swapon (8).
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An entry
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.I none
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is useful for bind or move mounts.
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More than one type may be specified in a comma-separated list.
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.BR mount (8)
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and
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.BR umount (8)
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support filesystem
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.IR subtypes .
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The subtype is defined by '.subtype' suffix. For
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example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
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any prefix to the first fstab field (for example 'sshfs#example.com' is
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deprecated).
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.RE
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.B The fourth field
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.RI ( fs_mntops ).
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.RS
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This field describes the mount options associated with the filesystem.
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It is formatted as a comma-separated list of options.
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It contains at least the type of mount
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.RB ( ro
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or
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.BR rw ),
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plus any additional options appropriate to the filesystem
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type (including performance-tuning options).
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For details, see
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.BR mount (8)
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or
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.BR swapon (8).
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Basic filesystem-independent options are:
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.TP
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.B defaults
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use default options: rw, suid, dev, exec, auto, nouser, and async.
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.TP
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.B noauto
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do not mount when "mount -a" is given (e.g., at boot time)
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.TP
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.B user
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allow a user to mount
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.TP
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.B owner
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allow device owner to mount
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.TP
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.B comment
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or
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.B x-<name>
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for use by fstab-maintaining programs
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.TP
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.B nofail
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do not report errors for this device if it does not exist.
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.RE
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.B The fifth field
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.RI ( fs_freq ).
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.RS
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This field is used by
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.BR dump (8)
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to determine which filesystems need to be dumped.
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Defaults to zero (don't dump) if not present.
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.RE
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.B The sixth field
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.RI ( fs_passno ).
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.RS
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This field is used by
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.BR fsck (8)
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to determine the order in which filesystem checks are done at
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boot time. The root filesystem should be specified with a
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.I fs_passno
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of 1. Other filesystems should have a
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.I fs_passno
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of 2. Filesystems within a drive will be checked sequentially, but
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filesystems on different drives will be checked at the same time to utilize
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parallelism available in the hardware.
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Defaults to zero (don't fsck) if not present.
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.SH NOTES
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The proper way to read records from
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.B fstab
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is to use the routines
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.BR getmntent (3)
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or
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.BR libmount .
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The keyword
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.B ignore
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as a filesystem type (3rd field) is no longer supported by the pure
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libmount based mount utility (since util-linux v2.22).
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.SH FILES
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.IR /etc/fstab ,
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.I <fstab.h>
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.SH "SEE ALSO"
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.BR getmntent (3),
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.BR fs (5),
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.BR findmnt (8),
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.BR mount (8),
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.BR swapon (8)
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.SH HISTORY
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The ancestor of this
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.B fstab
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file format appeared in 4.0BSD.
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.\" But without comment convention, and options and vfs_type.
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.\" Instead there was a type rw/ro/rq/sw/xx, where xx is the present 'ignore'.
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.SH AVAILABILITY
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This man page is part of the util-linux package and is available from
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https://www.kernel.org/pub/linux/utils/util-linux/.
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