On Fri, Apr 24, 2015 at 04:08:24PM +0200, Lentes, Bernd wrote: > Hi, > > it should be just a small problem, but it is one. How can I rollback to a snapshot of my root filesystem ? > Googeling, I found a lot of solutions, each different. > I finally choosed this one: https://btrfs.wiki.kernel.org/index.php/UseCases#I_want_to_be_able_to_do_rollbacks_with_Btrfs > > I made the snapshot, changed some configuration, and afterwards I'd like to rollback to the snapshot: > > - btrfs subvolume snapshot -r / /.snapshots/vor_nvidia You made a read-only snapshot. > - change some configuration > > - btrfs subvolume set-default 625 (id of the snapshot) > > - reboot ... so it's going to be read-only when you try using it as your root FS. :) > My /-folder is again the old one, that's ok. The change of the configuration has disappeared. But it is just read-only: > pc63422:~ # touch /test > touch: cannot touch '/test': Read-only file system > > mount says: > > ... > /dev/sda1 on / type btrfs (rw,ssd,space_cache) > ... > > It seems to be rw !? There's a bit of an awkward distinction here: subvolumes (and hence snapshots) have a read-only property which is entirely independent of the mount flags. So you've got a read-write mount (i.e. the VFS will allow a write attempt, and pass it down to the FS), but that part of the FS is itself read-only (so the FS will complain). What you should probably be considering is not using set-default, but instead using mount options (subvol=/path) to select the subvolume you want to mount. If you want to make a read-only snapshot into a read-write one, you can simply snapshot it again without the -r option. Hugo. -- Hugo Mills | Reading Mein Kampf won't make you a Nazi. Reading hugo@... carfax.org.uk | Das Kapital won't make you a communist. But most http://carfax.org.uk/ | trolls started out with a copy of Lord of the Rings. PGP: E2AB1DE4 |
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