Can 12.04 be installed using Btrfs only?

Solution 1:

You have been able to install Ubuntu into btrfs since 10.10

See the following guides

https://help.ubuntu.com/community/btrfs

http://ubuntuforums.org/showthread.php?t=1389279

With that said, see the stability section on the wiki

You can boot a btrfs root (/boot) partition with grub2 (1.99), but the initrd has to be compressed with zlib (not lzo)

Looking as /etc/initramfs-tools/initramfs.conf, gzip appears to be the default, you should be good to go.

And from the ubuntu wiki page I gave you :

As of 11.04-beta1, it is possible to use only btrfs file systems with the caveat that grub _MUST_NOT_ be installed to the boot sector of the btrfs volume containing /boot.

So install Ubuntu 11.04 or higher, be sure to install grub to the MBR (this is the default behavior of the installer).