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| .\" @(#)fstab.5 6.5 (Berkeley) 5/10/91 |
| .\" |
| .TH FSTAB 5 "February 2015" "util-linux" "File Formats" |
| .SH NAME |
| fstab \- static information about the filesystems |
| .SH SYNOPSIS |
| .I /etc/fstab |
| .SH DESCRIPTION |
| The file |
| .B fstab |
| contains descriptive information about the filesystems the system can mount. |
| .B fstab |
| is only read by programs, and not written; it is the duty of the system |
| administrator to properly create and maintain this file. The order of records in |
| .B fstab |
| is important because |
| .BR fsck (8), |
| .BR mount (8), |
| and |
| .BR umount (8) |
| sequentially iterate through |
| .B fstab |
| doing 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. |
| .PP |
| The following is a typical example of an |
| .B fstab |
| entry: |
| .sp |
| .RS 7 |
| LABEL=t-home2 /home ext4 defaults,auto_da_alloc 0 2 |
| .RE |
| |
| .B The first field |
| .RI ( fs_spec ). |
| .RS |
| This field describes the block special device or |
| remote filesystem to be mounted. |
| .LP |
| For ordinary mounts, it will hold (a link to) a block special |
| device node (as created by |
| .BR 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 |
| .BR 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 |
| .BR fstab . |
| .LP |
| 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 |
| .BR e2label (8), |
| .BR xfs_admin (8), |
| or |
| .BR fatlabel (8) |
| to set LABELs on filesystems). |
| |
| It's also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers |
| are supported for example for GUID Partition Table (GPT). |
| |
| See |
| .BR mount (8), |
| .BR blkid (8) |
| or |
| .BR lsblk (8) |
| for more details about device identifiers. |
| |
| .LP |
| Note that |
| .BR mount (8) |
| uses UUIDs as strings. The string representation of the UUID should be based on |
| lower case characters. |
| .RE |
| |
| .B The second field |
| .RI ( fs_file ). |
| .RS |
| This field describes the mount point (target) for the filesystem. For swap partitions, this |
| field should be specified as `none'. If the name of the mount point |
| contains spaces these can be escaped as `\\040'. |
| .RE |
| |
| .B The third field |
| .RI ( fs_vfstype ). |
| .RS |
| This field describes the type of the filesystem. Linux supports many |
| filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus, |
| tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more. |
| For more details, see |
| .BR mount (8). |
| |
| An entry |
| .I swap |
| denotes a file or partition to be used |
| for swapping, cf.\& |
| .BR swapon (8). |
| An entry |
| .I none |
| is useful for bind or move mounts. |
| |
| More than one type may be specified in a comma-separated list. |
| |
| .BR mount (8) |
| and |
| .BR umount (8) |
| support filesystem |
| .IR 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). |
| .RE |
| |
| .B The fourth field |
| .RI ( fs_mntops ). |
| .RS |
| This field describes the mount options associated with the filesystem. |
| |
| It is formatted as a comma-separated list of options. |
| It contains at least the type of mount |
| .RB ( ro |
| or |
| .BR rw ), |
| plus any additional options appropriate to the filesystem |
| type (including performance-tuning options). |
| For details, see |
| .BR mount (8) |
| or |
| .BR swapon (8). |
| |
| Basic filesystem-independent options are: |
| .TP |
| .B defaults |
| use default options: rw, suid, dev, exec, auto, nouser, and async. |
| .TP |
| .B noauto |
| do not mount when "mount -a" is given (e.g., at boot time) |
| .TP |
| .B user |
| allow a user to mount |
| .TP |
| .B owner |
| allow device owner to mount |
| .TP |
| .B comment |
| or |
| .B x-<name> |
| for use by fstab-maintaining programs |
| .TP |
| .B nofail |
| do not report errors for this device if it does not exist. |
| .RE |
| |
| .B The fifth field |
| .RI ( fs_freq ). |
| .RS |
| This field is used by |
| .BR dump (8) |
| to determine which filesystems need to be dumped. |
| Defaults to zero (don't dump) if not present. |
| .RE |
| |
| .B The sixth field |
| .RI ( fs_passno ). |
| .RS |
| This field is used by |
| .BR fsck (8) |
| to determine the order in which filesystem checks are done at |
| boot time. The root filesystem should be specified with a |
| .I fs_passno |
| of 1. Other filesystems should have a |
| .I 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 available in the hardware. |
| Defaults to zero (don't fsck) if not present. |
| |
| .SH NOTES |
| The proper way to read records from |
| .B fstab |
| is to use the routines |
| .BR getmntent (3) |
| or |
| .BR libmount . |
| |
| The keyword |
| .B ignore |
| as a filesystem type (3rd field) is no longer supported by the pure |
| libmount based mount utility (since util-linux v2.22). |
| |
| .SH FILES |
| .IR /etc/fstab , |
| .I <fstab.h> |
| .SH "SEE ALSO" |
| .BR getmntent (3), |
| .BR fs (5), |
| .BR findmnt (8), |
| .BR mount (8), |
| .BR swapon (8) |
| .SH HISTORY |
| The ancestor of this |
| .B fstab |
| file format appeared in 4.0BSD. |
| .\" But without comment convention, and options and vfs_type. |
| .\" Instead there was a type rw/ro/rq/sw/xx, where xx is the present 'ignore'. |
| .SH AVAILABILITY |
| This man page is part of the util-linux package and is available from |
| https://www.kernel.org/pub/linux/utils/util-linux/. |