fsck stands for "file system check" and it is used to check and optionally repair one or more Linux file systems. Normally, the fsck program will try to handle file systems on different physical disk drives in parallel to reduce the total amount of time needed to check all of the file systems (see ).
The Arch Linux boot process conveniently takes care of the fsck procedure for you and will check all relevant partitions on your drive(s) automatically on every boot. Hence, there is usually no need to resort to the command-line.
Boot time checking
There are two players involved:
- mkinitcpio offers you the option to fsck your root file system before mounting it via the
fsckhook. If you do this, you should mount root read-write via the appropriate
- systemd will fsck all file systems having a fsck pass number greater than 0 (either with #fstab options or a user-supplied unit file). For the root file system, it also has to be mounted read-only initially with the kernel parameter
roand only then remounted read-write from fstab (note that the
defaultsmount option implies
The first option is the recommended default, and what you will end up with if you follow the Installation guide. If you want to go with option 2 instead, you should remove the
fsck hook from
mkinitcpio.conf and use
ro on the kernel command-line. The kernel parameter
fsck.mode=skip can be used to make sure fsck is disabled entirely for both options.
Forcing the check
Alternatively, systemd provides initramfs. However, checking the root file system this way causes a delay in the boot process, because the file system has to be remounted., which checks all configured file systems, which were not checked in the
forcefsckto the root of each file system or using the command
-Fflag were only working for the old SysVinit and early versions of Upstart and are not working with systemd. The aforementioned solution is thus the only one working for Arch Linux.
Automatically answer yes to all repair questions
The boot time fsck checks might end up saying
"UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY."
This happens when you need to apply some changes to fix the file system which are not considered completely safe, and thus require fsck to be run manually.
You can set
fsck to automatically apply all suggested change (i.e. answer yes to all questions) by setting the
fsck.repair kernel command line option to
yes. (Other possible values are
preen.) Check the documentation for the meaning of these options.
Tips and tricks
Attempt to repair damaged blocks
To automatically repair damaged portions of an ext2/ext3/ext4 or FAT file system, run:
# fsck -a
Repair damaged blocks interactively
This is useful for when files on the boot partition have changed, and the journal failed to properly update. In this case, unmount the boot partition, and run the following code to repair damaged portions:
# fsck -r drive
Changing the check frequency
By default, fsck checks a file system every 30 boots (counted individually for each partition). To change the frequency of checking, run:
# tune2fs -c 20 /dev/sda1
In this example,
20 is the number of boots between two checks.
1 would make it scan at every boot, while
0 would stop scanning altogether.
If you wish to see the frequency number and the current mount count for a specific partition, use:
# dumpe2fs -h /dev/sda1 | grep -i 'mount count'
fstab is a system configuration file and is used to tell the Linux kernel which partitions (file systems) to mount and where on the file system tree.
/etc/fstab entry may look like this:
/dev/sda1 / ext4 defaults 0 1 /dev/sda2 /other ext4 defaults 0 2 /dev/sda3 /win ntfs-3g defaults 0 0
The 6th column (in bold) is the fsck option.
0— do not check.
1— first file system (partition) to check;
/(root partition) should be set to
2— all other file systems to be checked.
Can't run fsck on a separate /usr partition
- Make sure you have the required hooks in
/etc/mkinitcpio.confand that you remembered to re-generate your initramfs image after editing this file.
- Check your fstab! Only the root partition needs
1at the end, everything else should have either
0. Carefully inspect it for other typos, as well.
ext2fs: no external journal
There are times (due to power failure) in which an ext(3/4) file system can corrupt beyond normal repair. Normally, there will be a prompt from fsck indicating that it cannot find an external journal. In this case, run the following commands:
Unmount the partition based on its directory
# umount directory
Write a new journal to the partition
# tune2fs -j /dev/partition
Run an fsck to repair the partition
# fsck -p /dev/partition