I'm about to setup my new USB key with Grub or Grub2. In the old days I used ext2 for the boot partition.
I'm wondering if I could use ext4 for Grub2?
And if use Grub 0.9X, what about support of ext3?
Grub legacy (0.9x) supports ext2 and ext3 (ext3 is backward compatible with ext2) but not ext4 (unless you've turned off the backward-incompatible features, which doesn't leave much additional goodness compared with ext3). The development of Grub legacy stopped before ext4 was mature. There are unofficial patches to support ext4 on Grub legacy; the discussion on Debian bug #511121 has a pointer to two patches (one of which is in some versions of Ubuntu).
Grub2 (1.9x, more precisely since 1.97) supports ext2, ext3 and ext4, with the same module (
None of the new features of ext4 are particularly useful for a separate
/boot partition, so if that's what you have, you might as well stick to ext2. But if you keep your kernel and Grub configuration on the root partition, if it's ext4, make sure your Grub version is recent enough or patched.