Quoting Christian Brauner (christianvanbrau...@gmail.com): > On Mon, Sep 14, 2015 at 02:50:39PM +0000, Serge Hallyn wrote: > > Quoting Christian Brauner (christianvanbrau...@gmail.com): > > > When creating ephemeral containers that have the option lxc.ephemeral = 1 > > > set > > > in their config, they will be destroyed on shutdown. As they are simple > > > overlay > > > clones of an existing container they should be registered in the > > > lxc_snapshots > > > file of the original container to stay consistent and adhere to the > > > expectancies of the users. Most of all, it ensure that we cannot remove a > > > container that has clones, even if they are just ephemeral > > > snapshot-clones. The > > > function adds further consistency because remove_snapshots_entry() > > > ensures that > > > ephemeral clone-snapshots deregister themselves from the lxc_snapshots > > > file > > > when they are destroyed. > > > > > > POSSIBLE GLITCH: > > > I was thinking hard about racing conditions and concurrent acces on the > > > lxc_snapshots file when lxc-destroy is called on the container while we > > > shutdown then container from inside. Here is what my thoughts are so far: > > > > > > There should be no racing condition when lxc-destroy including all > > > snapshots is > > > > Note that lxcapi_destroy_with_snapshots() deletes the *snapshots*, not the > > snapshot clones. This is an unfortunate naming clash (which we could try > > to correct henceforth but we need good names :), but they are different. > > So anything under /var/lib/lxc/$container/snaps will be deleted. But if > > you've created an overlayfs clone, then containers listed in > > /var/lib/lxc/$container/lxc_snapshots will not be deleted. There is no > > API call or program to automatically deleted those right now. > > I think you are partially wrong here. I was not thinking about problems > created > by an API-call but by the lxc-destroy exectuable. A quick walkthrough: With > the
D'oh. Yeah, you'll need to mutex that somehow. > recent patches by me to lxc-destroy when I do: > > lxc-clone -s -B overlayfs -o w1 -n w2 > > the snapshot-clone will be registered in the lxc_snapshots file and when I > call > > lxc-destroy -n w1 -s > > the original container including all it's snapshot-clones will be destroyed > and > deleted from the lxc_snapshots file. This is done by having lxc-destroy open > the > lxc_snapshots file of the original container, reading in all snapshot-clone > entries in and deleting them. > > > think we want to write one, but a program to show which snapshots exist > > would be good). > > > > (Actually, there seems to be a bug right now - The sequence: > > > > lxc-create -t download -n w1 -- -d ubuntu -r wily -a amd64 > > lxc-clone -s -B overlayfs -o w1 -n w2 > > lxc-snapshot -n w2 > > lxc-snapshot -n w2 -r snap0 > > > > does not result in /var/lib/lxc/w2/snap0 being deleted, so a subsequent > > > > lxc-destroy -n w2 > > > > is refused. > > > > Do you have time to either look into that, or raise an issue on github > > about it? > > I'll take a look tonight. Don't know how fast I can fix this. > > > > > > called and the container in question is running, lxc-destroy will simply > > > fail > > > with the warning that the clone is still running but lxc-destroy won't > > > touch > > > the lxc_snapshots file. The offending container will then exit and delete > > > the > > > container entry. lxc-destroy can then be called again and will delete the > > > remaining containers. > > > > > > The strange case seems to be when we create another clone-snapshot while > > > another one shuts down. Does someone have any arguments against this way > > > of > > > > This should be fine, because mod_rdep does a container_disk_lock(c0). So > > the inc and dec will be mutually exclusive. > > > > > implementing it? Do we expect trouble? Do we need flocks in start.c and > > > lxccontainer.c? > > > > > > Christian Brauner (1): > > > Add remove_snapshots_entry() > > > > > > src/lxc/start.c | 123 > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 123 insertions(+) > > > > > > -- > > > 2.5.1 > > > _______________________________________________ lxc-devel mailing list lxc-devel@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-devel
