Arch Linux User Repository

I followed the guide in the wiki for setting up Arch on a btrfs-root. So my / is on the subvolume __active and that is also how it is set up in grub.cfg and fstab. Now gathering from the comments, I understand that this is not recommended? So should I strip the subvolume-option from fstab and/or grub.cfg? Also, am I right that this hook is only required for easy rollback support? So if I didn't need the rollback support, could I just stick with the ordinary btrfs hook? If that is the case... Does the ordinary btrfs hook require the subvolume flag to be present in grub.cfg and fstab or should they be removed still? Mind, I still want / to be on the subvolume __active. Thanks a bunch.

ah that makes sense, its probably pulling from the active mounts. i'll take a look tonight, thanks

Ah and I'd definitely recommend to either strip subvol= from the rootflags or prevent btrfs_advanced from appending another subvol option and thus disabling it's rollback feature with a warning message. As I wrote below specifying multiple of them causes the mount to fail and drops you to emergency console which is not what non-nerds want :)

It is all to get it working for me. I didn't change any of the default options, maybe some problems occur with other settings. Hm thanks for the advice, I did indeed add subvol=__active to /etc/fstab however it works even with this option for me. However grub-mkconfig adds the option independently from this: grub-mkconfig is a shell script, check it out, it uses among others /etc/grub.d/10_linux to generate the grub configuration. The latter executs 'grub-mkrelpath /' to get the subvolume and adds it to the kernel cmdline. (c.f. /etc/grub.d/10_linux and /usr/share/grub/grub-mkconfig_lib)

@buergi, nice, thanks :) i knew people were having some issue with GRUB2 but i havent been able to remedy (my $DAYJOB devel work is related to tax processing, needless to say, it's... busy); is this all you needed to add to get GRUB2 working? ...and how is the subvol option being added? NOTE: you should *not* be defining a subvol in your fstab (if that's where it gets it from) because it's impossible to change the rootfs subvol after initial mount (can only be done in initramfs), and it won't be accurate anyway (eg. when booting __rollback). i will fix these up ASAP, little late tonight, but tomorrow... esp. if you can confirm those things for me. thanks!

There are two little bugs in the hook which cause it not to work at all for me. The problems occur when using grub2's grub-mkconfig. As long as GRUB_DISABLE_LINUX_UUID is not set to 'true' in /etc/default/grub grub-mkconfig uses root=UUID=... and not /dev/sdXY. Therefore, one has to pass the lookup option to blkid. Furthermore, grub2 adds 'subvol=__active' to rootflags and btrfs_hook does so again. mount.btrfs however refuses to work with multiple subvol options so you are dropped to emergency console. The following patch adds the lookup option and strips all subvol=... options from rootflags. 109a110,111 > # strip all other subvol options from rootflags > rootflags="$(echo $rootflags | sed 's/subvol=[^,]*,\?//g;s/,$//g')" 227c229 < [ "$(blkid -s TYPE -o value ${root})" = btrfs ] || return 0 --- > [ "$(blkid -s TYPE -o value -lt ${root})" = btrfs ] || return 0 Hopefully this problems will be fixed soon, except from this problems this is a great and very useful hook. Thanks a lot xtfxme.

I am not seeing any rollback option during boot. Can have somebody plz have a look https://bbs.archlinux.org/viewtopic.php?pid=1173396#p1173396

@Vitok ... hmm, i'm not %100 sure what's wrong there, but it's likely related to the stuff @WorMzy was talking about (few comments back). i intend on reworking this hook very soon to take advantage of all the developments since its inception; i will ensure that multidevice stuff works properly.

My too can't boot a multi-device (raid0) using grub2. But I can't boot at all with this hook, not when root=UUID..., /dev/disk/by-uuid/..., or /dev/sda2. With original btrfs hook I can booting without rootflags=device=/dev/sd[ab]2 Without any btrfs related hook can boot with rootflags=device=/dev/sd[ab]2 With btrfs_advanced hook can't boot at all, always the same ends http://pastie.org/private/xq9dz6djc2tmgcmkmsw8a

@jim945, this hook -- from day one circa late 2009 -- was never needed to boot btrfs.