Monday, April 11, 2011

Converting an ext3 filesystem to ext4 on CentOS 5.6

If you recently installed CentOS 5.6 or updated to CentOS 5.6 you can now utilize the ext4 filesystem.

To do the conversion or create a new ext4 filesystem you need the e4fsprogs tool kit from yum.

#yum -y install e4fsprogs

I did this conversion on a test system with a non-root filesystem to avoid any possible problems. I also backed up the filesystem just in case something went terribly wrong.

First you need to un-mount the filesystem, as it cannot be in use.

#cd /; umount /dev/VolGroup00/LogVol00

Now you can run the tune4fs command to convert the filesystem to ext4.
#tune4fs -O extents,uninit_bg,dir_index /dev/VolGroup00/LogVol00

Now that the filesystem is ext4 it is no longer able to be mounted as ext3, so change its entry in the fstab.

#vi /etc/fstab

Now because we used the option uninit_bg we need to run fsck on the new ext4 filesystem. This is a good idea to do anyways, but is a requirement here.

#e4fsck -fDC0 /dev/VolGroup00/LogVol00

e4fsck will complain about "One or more block group descriptor checksums are invalid", this is totally normal.

Before doing these steps on the root filesystem (/) I would recommend you read over the Ext4 Howto on kernel.org. I re-wrote the steps for more accurate information pertaining specifically to CentOS 5.6 and my system.

As always:

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4 comments:

Matt said...

Cool! Any performance increases that you've seen?

Steve.Lippert said...

Yesterday was mainly about testing the procedure and less about speeding anything up. I ran it on a test system that I have on a file system that holds my clonezilla images, so I don't expect to see a whole lot of difference. I will look into this a bit more when I run this on my main storage systems.

any said...

Great guide, thank you very much!

Anonymous said...

You cannot just umount the root filesystem or you will get:
umount: /: device is busy

You have to boot from an install cd and then get a command prompt.