Repairing Linux ext2 or ext3 or ext4 File System [ fsck ]

Posted on in Categories Data recovery, Debian Linux, Gentoo Linux, RedHat/Fedora Linux, Tips last updated October 16, 2005

Linux comes with the system utility fsck (“file system check”) for checking the consistency of a file system. This quick post explains how to use fsck to fix error.

The syntax is as follows to check and optionally repair one or more Linux file systems:

fsck Fs-Name-Here
fsck /dev/xyz
fsck /home
fsck.ext3 /dev/hdc1
fsck.ext2 /dev/flash/device/name

Fs-Name-Here can be one of the following

  1. A device name (e.g. /dev/hda1, /dev/sda2, /dev/md0, /dev/vg1/volume_1)
  2. A mount point (e.g. /var, /home)
  3. An ext2 label (e.g. LABEL=home )
  4. UUID specifier (e.g. UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd)


First, a file system must be unmounted. You cannot repair it while it is running. Take system down to runlevel one (make sure you run all command as root user):
# init 1

Next, unmount file system, for example if it is /home (/dev/sda3) file system then type command:
# umount /home
# umount /dev/sda3

Finally, run fsck on the partition, enter:
# fsck /dev/sda3
However be sure to specify the file system type using -t option. Recently, one of our sys admin run the command on ext3 file system w/o specifying file system. Result was more corruption as fsck by default assumes ext2 file system:
# fsck -t ext3 /dev/sda3
# fsck.ext3 /dev/sda3
# fsck.ext4 /dev/sda5
If you do not know your file system type then typing mount command will display file system type.
$ mount
Sample outputs:

/dev/root on / type ext4 (rw,relatime,barrier=0,journal_checksum,data=ordered)
/tmp on /tmp type tmpfs (0)
none on /dev/pts type devpts (gid=4,mode=620)
/sys on /sys type sysfs (0)
/proc/bus/usb on /proc/bus/usb type usbfs (0)
/dev/vg1/volume_1 on /volume1 type ext4 (usrjquota=aquota.user,,jqfmt=vfsv0,synoacl)
[email protected] on /opt type bind (bind)
none on /proc/fs/nfsd type nfsd (0)

fsck will check the file system and ask which problems should be fixed or corrected. If you don’t want to type ‘y’ every time then you can pass -y option to fsck:
# fsck -y /dev/sda3
Please not if any files are recovered then they are placed in /home/lost+found directory by fsck command.

Don’t execute, just show what would be done:
# fsck -N /dev/sda3

Once fsck finished, remount the file system:
# mount /home

Go to multiuser mode, enter:
# init 3
Read man page of fsck for more information. Make sure you replace /dev/sda3 with your actual device name:
$ man fsck

Page last updated at 9:58 PM, April 10, 2012.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

22 comment

  1. Commands are same but syntax changes.

    To repair HFS file system (/home)

    umount /home
    fsck –F hfs /dev/vg00/lvo1
    mount /home

    To repair JFS file system (/home)
    umount /home
    fsck –F vxfs /dev/vg00/lvo14
    mount /home

    Replace /dev/XXX/YYY with actual device file.

    1. To repair a file system in HPUX

      # fsck -F vxfs -y -o full /dev/vg##/lvol#
      # fsck -F vxfs -o full -y /mount_pt

      Note: The HFS file system has been obsoleted in HP-UX since version 10, except for the /stand file system which contains the kernel, and you’re not going to unmount the kernel and run a file system check. Instead, get to single user. Here is one way:

      # reboot
      # interact with IPL . yes
      ISL>hpux -is

      And as the kernel is loaded vg00 will be enabled and automatically checked for corruption.

      # init 2, same thing, automatically check run level 2
      # init 3, same thing, automatically check run level 3, multiprocessor mode. The system is up.

      NEVER! fsck /stand – The only hfs file system for over a decade is /stand, and you never fsck /stand!

  2. Thankyou – this page saved my life! (well, not literally). After checking loads of links that just told me what it said in the man page, here was a quick, easy and practical way to use the command.

  3. This post is over two years old but still relevant today.

    I just used most of the steps described here to repair an ext3 partition on my Ubuntu desktop system. Only difference being I did not do “init 1”. I logged out to the gdm screen then did Ctl-Alt-F2 to get to a virtual console. I logged into the system and ran the commands with the exception of “init 1”.

    Thanks for a very helpful and concise article.

  4. system not booting.because new root user created last time,not come guimode .so restart that p.c .not booting asked password or alt ctrl i gave that password .system restarted.what will i do?lasttime i worked that pc du /dev/hdc6 .but i don’t know about this cmd.may be reason is there

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