On Mon, Jan 09, 2012 at 04:21:31PM +0100, Niels de Carpentier wrote:

quoted

quoted

The plan that occurs to me is to make a snapshot of the system in the
state that I want to always boot.  Then, I would rewrite the init
script in the initrd to (a) delete any old tmp copy of the snapshot;
(b) copy the static snapshot to a tmp copy; (c) mount the tmp copy.

That's a little harder than I was hoping to work -- is there an easier
way to get this functionality?

I would just create a filesystem with the static content, and on boot
do:

mount fs
delete snapshots
create snapshot
unmount fs and mount snapshot.

I'm not sure if you can snapshot a snapshot, otherwise you could start
with a snapshot as well. (Just be sure not to delete it)

   Yes, you can make snapshots of snapshots. A btrfs snapshot is a
first-class citizen -- there's no real distinction between the
original subvolume and a snapshot of it.

Good! That makes the op's case real simple. No need to copy any data, just
snapshot and mount.

Niels