Get to know the fsck command

Environmental Variables

Environmental Variables can have as much effect on fsck's behavior as the available options. The command's man page includes these variables:

  • FSCK_FORCE_ALL_PARALLEL: Sets fsck to run in parallel. This setting helps fsck to run on RAID systems or on filesystems on the same device.
  • FSCK_MAX_INST: Sets the maximum number of filesystem checks that can run at the same time so that system resources are overloaded. 0 means that no limit is set and is currently the default, although the man page hints that might change in later releases.
  • PATH: Sets the directories where fsck should look for filesystem checkers. Fsck searches /sbin, /sbin/fs.d, /sbin/fs, /etc/fs, and /etc, then the directories in the path.
  • FSTAB_FILE: Sets an alternate location for /etc/fstab, allowing users to test fsck with less worry over consequences.

Taking Control

Faced with the need to check a filesystem, many users – including me – often simply enter the filesystem. Sometimes, that is all that is needed, but it leaves you helpless if the problem remains unsolved.

If you learn more about fsck's capabilities, however, you can consider the options systematically instead of panicking. Just remember that, when all repairs are made, you should remount each filesystem or else reboot.

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