From: James Bensley jwbensley@gmail.com
I have a 5.5 box and I have formatted a partition as ext4 however I can't mount it, the mount command is telling me its an unknown file system type. fsck tells me the partition is a clean ext4 partition but I can't mount it. Some reasearch has lead me to believe the problem is that ext4 isn't enabled in the kernel by default in 5.5 (this was originally a 5.2 box that has been upgraded over time, its now on 2.6.18).
I guess you have e4fsprogs installed? I saw some people use tune4fs -E /dev/sdxx before trying to mount...
JD