On Jan 6, 2013, at 7:44 AM, Gene Czarcinski <gene@xxxxxxxxx> wrote: > On 01/05/2013 04:27 PM, Chris Murphy wrote: >> On Jan 5, 2013, at 2:17 PM, Gene Czarcinski <gene@xxxxxxxxx> wrote: >> >>> As of the latest updates to anaconda and grub2 for Fedora 18, it is now possible to install with /boot as a btrfs subvolume. The way that grub2 is handling this is the "reach down" to the files it needs as if the subvolume was a directory. >>> >>> Is this OK? >> Mostly, but getting GRUB2 to handle subvolid I think would be better, because then subvols can be moved/renamed and things still would work. >> >> Small problem currently is Fedora 18 still depends on grubby to make grub.cfg changes, and grubby is being kinda dumb about updating grub.cfg when /boot is on a boot subvol - ergo there's an error and it doesn't update the grub.cfg correctly. >> https://bugzilla.redhat.com/show_bug.cgi?id=864198 >> Work around after any kernel update is to run grub2-mkconfig -o /boot/grub2/grub.cfg manually, and then the grub.cfg is correct. >> >>> At this point I am not worried about snapshots or any other complexities. If the subvolume name is known. should grub2 be able to reliably "reach down" as if that subvolume was a directory? It needs some of its configuration files and, of course, the linux kernel. >> It's two parts. GRUB's core.img code works as you describe. But grub-install and grub-mkconfig depend on /etc/fstab. If I use subvolid= in /etc/fstab and update either core.img or grub.cfg (with -install or -mkconfig), then the system is no longer bootable. > So, I conclude from the above that the "safe" thing to do is to keep /boot as a separate ext2/3/4 partition. It depends on what you're comparing. And also what you mean by "not safe". fstab using labels with ext[234] could see a conflict one day, just the same as possibly renaming/moving a Btrfs subvolume used for boot, or even root for that matter. If you use UUID, and you use subvol=, and you don't rename/move your subvolume, it's perfectly safe. Nevertheless, GRUB becoming subvolid aware seems like a good idea to me, but I have no idea what's involved in that. Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
