Bruce Jerrick wrote: > Despite ext4[dev] support in Fedora 9 and 10, conversion of an ext3 filesystem > to ext4 will render it permanently unbootable (read on; there's a "yes, I know" > down there). > > I'm not looking for a rescue (this was all done to an expendable system), and > it appears to be a known "issue", but additional warnings in 'man tune2fs' > (or even in the executable) seem to be warranted. > > The scenario was: > > On a multi-boot machine with my main system being Fedora 8 (with > kernel-2.6.26.6-49.fc8 and e2fsprogs-1.41.3-2.fc9, so it has ext4dev support), > I "converted" an ext3 filesystem by setting 'test_fs' with tune2fs, then > mounting it (successfully) under the F8 system as type ext4dev. > > The converted filesystem contained an F10 installation all on one filesystem, > i.e., no separate /boot . (I had overlooked the fact that the anaconda > installer doesn't support ext4 on a bootable partition; the goal was just to > make sure I can access F10 ext4 filesystems from the F8 system.) Later I > discovered that the F10 system wouldn't boot, with a message about > "unsupported features". Yep, afraid grub doesn't support it yet. See below (or Peng's email) > Presumably this was because it now uses extents instead of indirect blocks > (after it was ext4, I modified a file on it, so I assume it started > using extents). The really bad news is that this conversion seems to > be irreversible. So there should probably be warnings in 'man tune2fs' > similar to those in 'man mkfs.ext4' (and also a warning about rendering a > partition permanently unbootable). Warnings might be in order, although tune2fs warning that some other applications may not yet grok ext4 seems above & beyond the call of duty; Fedora release notes might have been a good place for it ... It's sorta-reversible; see below. > BTW, there's a minor inconsistency in F10 'man mke2fs' (and its hardlink > clones). In the OPTIONS section, "-O" has "extent" listed, but the example > after "-t fs-type" uses "-O extents" (granted, either form seems to be > accepted). > > Similarly, 'tune2fs -l' reports "extent" (in Filesystem features), but > /etc/mke2fs.conf uses "extents" (as a features value). Yeah, I've noticed those too. > -- Bruce Jerrick > > PS. If feasible, a two-way ext3 <-> ext4 converter would be nice. You can do it manually by mounting w/o extents (-o noextents) and then for each extent-based file, cp $FILE $FILE.bak; mv $FILE.bak $FILE, and when that is all done, remove the extents flag. > PPS. Are bootable ext4 partitions in the cards? (I assume yes.) Yep, as Peng Tao said, there is a patch, and I've sent it to our grub maintainer; filing a fedora bug/rfe might kick that along a bit :) > PPPS. Why am I still using F8? <flame> Because gnome-session/gnome-terminal > save/restore is (repairably) broken in F9 and gone entirely in F10. </flame> Filed a bug? -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
