HOWTO: Repair a broken Ext4 Superblock in Ubuntu
This has happened to me a few times, and it’s not a nice problem to find yourself in. You computer won’t boot, all your filesystem checks tell you you’ve a bad superblock, but you cant seem to find how to fix it. Well, here goes :)
This guide is for ext4 , though I’ll explain how other filesystems can be cured along the way. The easiest way to carry all this out, seeing as your computer probably won’t boot at this stage, is to download and burn a copy of Parted Magic. Boot from that, and you’ll access to a number of useful tools.
First, figure out what partition we’re dealing with.
sudo fdisk -l
The above will list all the partitions on all the drives in your computer. To recover a lost partition, your going to need Testdisk. Testdisk is included in Parted Magic, and there’s a great guide on their site. For this though, we just need the partition number, such as /dev/sda3 or /dev/hdb1.
Now, make sure your superblock is the problem, by starting a filesystem check, replacing xxx with your partition name. Here, you can change ext4 to ext3, or ext2 to suit the filesystem.
sudo fsck.ext4 -v /dev/xxx
If your superblock is corrupt, the output will look like this
fsck /dev/sda5 fsck 1.41.4 (27-Jan-2009) e2fsck 1.41.4 (27-Jan-2009) fsck.ext4: Group descriptors look bad... trying backup blocks... fsck.ext4: Bad magic number in super-block while trying to open /dev/sda5 The superblock could not be read or does not describe a correct ext4 filesystem. If the device is valid and it really contains an ext4 filesystem (and not swap or ufs or something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock: e2fsck -b 8193 <device>
Now lets find where your superblock backups are kept.
sudo mke2fs -n /dev/xxx
Down at the bottom of this output, should be a list of the backups
Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208
Your almost there. Finally, restore the superblock from the backup, again replacing the x’s with your partition name, and block_number with the first backup superblock.
sudo e2fsck -b block_number /dev/xxx
Now reboot, and your superblock should be fixed. If it’s not, repeat the steps, but restore a different backup superblock :)
Filed under: Operating Systems, Ubuntu | 145 Comments
Tags: Ext4, Ubuntu
AMD64 Apt Apt-Cacher Apt-Cacher-NG Arch ArchBang Artic Silver 5 Backups Bang86 Broadband Celeron CentOS Cleaning Clonezilla Compiz Conky copy recursively CPU Crunchbang Debian DPKG Ebay find Firefox Flash Gnome GRUB GTk Hardware Heatsink HowTo Jesred Karmic Laptop Linux LUbuntu Maverick Network New Computer NTFS Nvidia Office 2007 Openbox Operating Systems Packages Packard Bell Pentium Pentium IV Perlico PIII postaweek2011 Posts Proxy RAID Repairs RSync Sensors Server Size Mismatch Snow Squid SSH Synaptic System64 Tecra terminal commands Themes Ubuntu Upgrade USB VNC W2K3 Windows Wine Xubuntu 9.10
- HOWTO: Repair a broken Ext4 Superblock in Ubuntu
- HOWTO: Fix an NTFS partition in Ubuntu
- HOWTO: Mount Partitions in Terminal - FSTab
- HOWTO: Start VirtualBox VM on boot - Windows
- HOWTO: Completely Remove ubuntu-desktop
- HOWTO: Apt-Cacher-NG on Ubuntu
- HOWTO: Disable Suspend and Hibernate – Ubuntu
- HOWTO: Gnome CentOS VNC Server
- HOWTO: StartX automatically on Login - Ubuntu
- HOWTO: Conky - IP monitor
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.