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I installed Natty 64-bit with btrfs filesystem only to find that it takes almost two minutes to boot. I tried a few different things, and finally today opened up /etc/fstab only to find the following:

UUID=b22ac5c7-e294-4d62-8189-6a3707148927 /      btrfs  defaults,subvol=@     0  1
UUID=b22ac5c7-e294-4d62-8189-6a3707148927 /home  btrfs  defaults,subvol=@home 0  2
UUID=24b7732d-f2f4-43a2-85c1-05b889a56524 none   swap   sw                    0  0

I only vaguely remember the installation process, but it seemed pretty simple at the time, and I don't remember creating any sub volumes. I tried editing the first two entries to show a single entry (with lzo compression):

UUID=b22ac5c7-e294-4d62-8189-6a3707148927 /      btrfs  defaults,compress=lzo 0  1

and it wound me up with nothing in my home directory, but booted much faster than before, just over one minute.

So, my question is, how do I go about putting / and /home on a single volume in fstab, rather than two subvolumes?

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my understanding of btrfs is that your approach of just mounting, without the subvol flag, should have worked; did it create a home directory that was empty, or did it result in a filesystem devoid of a home directory? – thomas michael wallace Jul 21 '11 at 13:27
it created an empty home directory. – yuttadhammo Jul 21 '11 at 16:19

You repartition, format the new partition, and mount it as /home, but that would defeat one of the big reasons to use btrfs in the first place. The ability to have different subvolumes without having to have a completely separate partition is one of the much anticipated features of btrfs.

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Thanks, but I don't get why I want my home directory on a different volume at all... it seems to slow down the boot process by about 60 seconds. Isn't it possible to just copy my home directory to the first subvol, then resize that subvol to take up the whole partition? What's wrong with having the /home dir in the same volume as / ? – yuttadhammo Jul 21 '11 at 15:57
this would work, although i think i've read somewhere that btrfs subvolumes on ubuntu are immutable (ie. you couldn't delete it, and may struggle to make it smaller.) – thomas michael wallace Jul 21 '11 at 16:22
yeah, just read that here: – yuttadhammo Jul 21 '11 at 16:29

I've just googled about, and the slow boot time you're experiencing maybe down to the (largely useless) fsck utility for the btrfs.

You can try removing (make a backup first!) the /sbin/fsck.btrfs link, which will prevent it checking your drive, and may prevent the delays at boot.

share|improve this answer
Thanks, will do... in the meantime, I've copied both / and /home over to an ext4 drive and it's amazing the difference in boot speed! It looks like my btrfs drive has two entries, @ and @home. What if I just put everything in both entries into the root directory, edit the fstab as above, and delete both @ and @home? Guess I can only try :) – yuttadhammo Jul 22 '11 at 2:54
I think the entries (subvolumes) cannot be deleted using ubuntu, so you may just end up loosing disk space. You may just want to consider not using btrfs at the moment, as it still appears to be under development and aimed at people with significant storage requirements (unless you're mucking in with development?) – thomas michael wallace Jul 22 '11 at 8:58
nah, just greedy for the cutting edge... I almost considered installing Oneiric as a result of this problem, that's how silly I am. I'm going to stick with ext4 for now - 20 second boot! – yuttadhammo Jul 22 '11 at 14:05

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