On 3/18/15 14:55 , Hugo Mills wrote:
On Wed, Mar 18, 2015 at 02:39:26PM -0700, K Richard Pixley wrote:
On 3/18/15 14:06 , Chris Murphy wrote:
The Fedora/RHEL/CentOS installer creates two subvolumes: root and
home. If you check out fstab, those subvolumes are mounted at /
and /home. Therefore the top level subvolume (id 5) is not mounted
by default, so there's no way to delete subvolumes in the top
level.
Ah! Thank you. That's the piece I was missing.
IMO, someone needs to take a clue-by-four to the heads of the
Fedora/RHEL/CentOS installer folks. I see no reason for this with
btrfs.
Actually, it's the recommended approach.
We've found over time that nesting subvolumes inside each other is,
in general, more trouble than it's worth. It makes it harder to do
things like take snapshots and then replace the original with a
snapshot (e.g. rollback to an earlier state).
Arranging the subvolumes with the top level (subvolid=0) as nothing
but a store for subvolumes means that you don't get the subvolumes
tangled up with each other, so it's much easier to manage them in
general.
There's a few cases where nesting subvolumes is helpful, but that's
more to do with preventing snapshots being taken of some pieces of the
filesystem.
Yes, I understand about the flat arrangement. It's been that way for
years now.
My complaint is a) about multiple subvols and b) about an unnecessary
and redundant subvol for the top level file system.
The redundancy should be obvious. And the problem with multiple subvols
is that they aren't needed and make snapshotting an entire system more
difficult than it needs to be. I want to be able to snapshot and
chroot. The traditional reason for partitioning a disk was to isolate
errors and to firewall "out of space" usage. Neither of those really
apply to btrfs as far as I can see.
I would much rather the installer simply create a single file system and
mount the partition directly rather than through a superfluous subvol.
I've never seen it done any other way as you might guess from my
confusion above.
--rich
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