fstab (File System table) is a file configuration that let us to define how and where disk partitions should be mounted into the filesystem. It contains a table representation of each file system, where they are mounted, what type of filesystem is used, type of mounting, ...
Each filesystem is described in a separate line.
Each line is composed of 6 columns separated by a blank space or a tabulation.
Here are the columns :
<filesystem> <mounting path> <filesystem type> <options> <dump> <fsck>
Example of a fstab content :
UUID=swswswsw-r2d2-cp30-&bb8-swswswswswsw /home ext4 defaults 0 1
The first column indicates the filesystem (partition, disk, ...). It can be specified with different options :
- Descriptors
/dev/sda1 - Labels
LABEL=HOME - UUIDs
UUID=abcdef... - GPT parition UUIDs
PARTUUID= - GTP patition labels
PARTLABEL=HOME
The second column indicates the mounting point in the OS filesystem. It can be any folder in the filesystem.
For a partition that doesn't have a mounting point (like swap parition), we can use the value
none.
The third column indicates the type of filesystem used for the partition.
For instance : ext2, ext3, ext4, xfs, btrfs, vfat, swap, ...
For ntfs we have to install ntfs-3g
The fourth column indicates some particular options for during the mounting process. They are the same options used with the command mount :
| option | description |
|---|---|
| defaults | default options if we don't really know the others options :) equivalent to rw,suid,dev,exec,auto,nouser,async |
| auto | the filesystem should be automatically mounted at startup or when the command mount -a is executed |
| noauto | only mounted when we told it to be mounted |
| exec | binaries can be executed |
| noexec | binaries can't be executed |
| user | users can mount the filesystem (without root privileges) |
| nouser | only root can mount the filesystem |
| ro | mount as read-only |
| rw | mount as read and write |
| sync | I/O done synchronously (handle single process) |
| async | I/O done asynchronously (can handle mutltiple I/O) |
| suid | authorize suid and sgid (get the owner permissions when executing the owner's binary) |
| nosuid | unauthorize suid and sgid |
| discard | activate TRIM option on SSD (better data management) |
| nofail | allow the boot sequence to continue even if the drive fails to mount |
| ... | ... |
These options can be mixed together with a
,. Example :UUID=swswswsw-r2d2-cp30-&bb8-swswswswswsw /home ext4 async,auto,noexec 0 1
The fifth column indicates the dump option. Dump is a backup program. If the value is set to 1, the filesystem will be backup with dump and not if it's set to 0.
The program dump is needed for this option, it is usually not installed so it can be set to 0.
The sixth column indicates the fsck (File System Check). It will check the integrity of the filesystem by priority :
- Value 1, it will be checked first.
- Value 2, it will be checked after 1.
- Value 0, it won't be checked.
Updated : 26/01/2021
Author : AnthonyF