ext4.wiki.kernel.org makes it sound like e2fsck was simply renamed to e4fsck so that e4fsprogs and e2fsprogs could coexist without overlapping. However, there is no mention of any difference in the code of the command.
The e2fsck man page makes no mention of ext4, but does mention that it works with ext3 (i.e. ext2 with journaling turned on).
And of course there's good ol' vanilla fsck which itself makes no mention of ext4.
If I need to fsck an ext4 file system on a RHEL based system, which tool do I use? e4fsck? But if it's just a rename of e2fsck, can I just use that instead? Why does Ubuntu mention ext4 in its e2fsck man page but no one else seems to? And what about plain fsck on ext4?
On a Fedora 14 machine there is fsck.ext4, fsck.ext3 and fsck.ext2 in /sbin/. They all have the exact same file size. Curioser and Curioser.
Furthermore, when running fsck.ext4, you see that it appears to be e2fsck running. For example, I see this line when running fsck.ext4:
e2fsck: aborted Tricksters!