Monday, May 23, 2011

[rydbhsng] Ubuntu Natty btrfs notes

Tried installing Ubuntu 11.04 Natty Narwhal 32-bit from the Alternate CD.  Partition set up was a unencrypted ext4 /boot partition, and dm_crypt encrypted partition, within which was LVM (lvm2), within which was a btrfs root partition and swap.

Install performance is SLOW!  After a few iterations, I report that btrfs (unencrypted) takes more than twice as long to install than ext4 (unencrypted).

But back to encrypted: Ran into Bug #757631 on Launchpad. Upon first boot after install, it drops into a Busybox after typing in the dm_crypt password.  Tried recovery mode.  After typing in dm crypt password

No init found. Try passing init= bootarg.
Busybox v1.17.1 (Ubuntu 1:1.17.1-10ubuntu-1) built-in shell (ash)
Enter 'help' ...
(initramfs) prompt

The 'find' command shows linux installed and visible in /root/@/.

"exit" kernel panics

Workaround: in grub, add 'rootflags=subvol=@' in the space between the ro and quiet. (I discovered the workaround independently by comparing grub.cfg in encrypted an unencrypted installations.)

See also Ubuntu Release notes.

Given the potential for btrfs failure, I'm going to create an additional ext4 partition in LVM for "precious" data. But alas, (in another reinstall), this does not seem to have worked. On first boot, it cannot mount the volume. I removed it out of fstab. I was unable to run fsck.ext4 (device or resource busy). Booting into a Maverick LiveCD, fsck reported (I think) volume header invalid, the page after page of errors. Did this thing ever even get formatted? Reminds me of the ext4 corruption (in Maverick) that prompted me to do this reinstall in the first place. But this time, rather than let fsck try to fix it, I ran mkfs.ext4 from the Maverick LiveCD.

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