CentOS 5 :: 5.5: Migrating Root (and Any Other) Partition From Ext3 To Ext4?

With the release of CentOS 5.5 ext4 is considered stable in this distribution so I decided to migrate to it. Luckily I started from migrating fresh server with CentOS 5.5 using some instruction I found on the internet. I think I shouldn�t say, that I screwed the whole thing up ;) After about 6 hours cursing, kicking, and crying I solved the task and figured the correct sequence of actions. The small problem with migrating root partition is that you can�t unmount it BTW.

During migration task, I found, that CentOS 5.5 rescue mode is somewhat broken a little in terms of ext4 support. It can mount ext4 partitions successfully. But its e2fsprogs package (tune2fs, e2fsck etc.) doesnt see ext4 partitions and say, that superblock is corrupted on a partition once is converted to ext4 (at least it did it for me. May be I should force filesystem type with -t ext4 switch?). Keep in mind, that if you screw your system up too badly, you will not be able to run tune2fs and e2fsck on it from rescue modeBut you will still able to mount it if it is not corrupted badly. In all below examples,Boot your system normally and login as root. Upgrade kernel if you wish (I usually use yum upgrade to upgrade all on new machines). Then upgrade/install some other packages