Comment 20 for bug 712029

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Colin Watson (cjwatson) wrote : Re: [Bug 712029] Re: ubiquity btrfs install fails to boot (grub rescue> prompt)

The @ directory is a subvolume. Even if you don't need subvolumes at
installation time (although the installer does create them in some
cases, in order to support cunning tricks by update-manager later on),
the way btrfs works is that you need to create at least one subvolume
up-front otherwise you have to completely reorganise your filesystem if
you ever need to use the feature in the future.

You can use 'mount -o subvol=@' to mount the appropriate subvolume.

I'll give this another try in the coming week. The annoying thing is
that GRUB's btrfs support works *some* of the time, and has stubbornly
refused to fail when I'm trying to debug it. Could you please file a
new bug on the grub2 package in Ubuntu (don't search for duplicates -
I'd prefer a fresh bug report in this case), and describe exactly how
you reproduced this bug? Ideally, I'd like something as close as
possible to a recipe that I can use in a virtual machine.