Can I run fsck or e2fsck when Linux file system is mounted?

Q. Can I run fsck or e2fsck command when Linux file system is mounted? Do you advice to run fsck on a live file system? I am using Cent OS.

A. No. Do not run fsck on a live or mounted file system. fsck is used to check and optionally repair one or more Linux file systems. Running fsck on a mounted filesystem can usually result in disk / data corruption. So please do not do it. You have two choices
(a) Take down system to single user mode and unmout system

(b) Boot from the installation CD into rescue mode

(a) Take down system to single user mode and unmout system

Following are steps :
=> Use init (process control initialization ) command to change runlevel 1 (singe user mode)
=> Use umount command to unmount /home file system
=> Run fsck using fsck command

Let us say you would like to run fsck on /home (/dev/sda3):

# init 1
# umount /home
# umount /dev/sda

# fsck /homeOR
# fsck /dev/sda3OR
# e2fsck -y /dev/sda3

(b) Boot from the installation CD into rescue mode

If you are using Cent OS/Fedora Core/RHEL linux, boot from first CD and at boot prompt type linux rescue nomount:
boot: linux rescue nomount

Now make new node for disk and partition 3:
# mknod /dev/sda
# mknod /dev/sda3
# fsck /dev/sda3

OR
# e2fsck -y /dev/sda3

Don't forget to reboot the system:
# exit;exit
# reboot

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{ 4 comments… read them below or add one }

1 Yaw 10.02.07 at 2:38 pm

l will like to know the big difference between fsck and e2fsck commands.

2 thewordsmith 08.13.08 at 5:24 pm

That advise above worked great. But I used to be able to rub “shutdown -rF 0″ to force fsck to run on reboot. But as of Fedora 9 on my i686 32 bit system the -F option is missing. Is there any way to get that option back in the shutdown menue?

3 Victor Vitayaudom 03.25.09 at 9:22 pm

No …

read http://linux.die.net/man/8/fsck and suggest flag -n if mounted

For some filesystem-specific checkers, the -n option will cause the fs-specific fsck to avoid attempting to repair any problems, but simply report such problems to stdout. This is however not true for all filesystem-specific checkers. In particular, fsck.reiserfs(8) will not report any corruption if given this option. fsck.minix(8) does not support the -n option at all.

4 source 06.16.09 at 2:47 pm

This worked great. I was able to rescue a downed system.

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