Interrupted lxc-snapshot deletes snapshot *and* vm

[Chris West]

lxc is configured for limited user usage, i.e. the backing store is always "dir". Let's create a container, and snapshot it in its pristine state:

% lxc-create -n restorebug -t download -- -d ubuntu -r utopic -a amd64 && lxc-snapshot -n restorebug
[...]
lxc_container: lxccontainer.c: lxcapi_snapshot: 3011 Snapshot of directory-backed container requested.
lxc_container: lxccontainer.c: lxcapi_snapshot: 3012 Making a copy-clone.
[...]

% ls ~/.local/share/lxc/restorebug/rootfs ~/.local/share/lxc/restorebug/snaps/snap0/rootfs
.local/share/lxc/restorebug/rootfs:
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var

.local/share/lxc/restorebug/snaps/snap0/rootfs:
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var

Everything went to plan. Now, try restoring the snapshot, and ctrl+c'ing lxc-snapshot while it's running:

% lxc-snapshot -n restorebug -r snap0
[ctrl+c, bang!]

Depending on when you press it, you might get some rsync output, but never anything from the lxc-snapshot command itself. This isn't unexpected, it's probably just copying the snapshot over to the vm, right?! That sounds cancellable. e.g.
rsync error: received SIGINT, SIGTERM, or SIGHUP (code 20) at rsync.c(632) [sender=3.1.1]
rsync error: received SIGINT, SIGTERM, or SIGHUP (code 20) at io.c(504) [generator=3.1.1]

Now, let's run lxc-snapshot again, no need to ctrl+c it:
% lxc-snapshot -n restorebug -r snap0
lxc_container: bdev.c: bdev_copy: 3253 failed to detect blockdev type for ...local/share/lxc/restorebug/snaps/snap0/rootfs
lxc_container: lxccontainer.c: copy_storage: 2543 Error copying storage
lxc_container: lxccontainer.c: lxcapi_destroy: 2141 Container restorebug has snapshots; not removing
lxc_container: lxc_snapshot.c: do_restore_snapshots: 109 Error restoring snapshot snap0

% ls -a ~/.local/share/lxc/restorebug/rootfs ~/.local/share/lxc/restorebug/snaps/snap0
.local/share/lxc/restorebug/rootfs:
. ..

.local/share/lxc/restorebug/snaps/snap0:
. .. config ts

It's deleted both the snapshot, and the original container. Further attempts to run lxc-snapshot give similar errors:

% lxc-snapshot -n restorebug -r snap0
lxc_container: lxccontainer.c: lxcapi_snapshot_restore: 3217 Failed to find original backing store type
lxc_container: lxc_snapshot.c: do_restore_snapshots: 109 Error restoring snapshot snap0

Also reproduced on cleaner utopic server installs, this bug report is from my laptop.

(We hit this on our build server: a typical job is to restore a vm, then run some commands in it. Jobs are cancellable, which just interrupts any running process.)

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: lxc 1.1.0~alpha2-0ubuntu3
ProcVersionSignature: Ubuntu 3.16.0-29.39-generic 3.16.7-ckt2
Uname: Linux 3.16.0-29-generic x86_64
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
Date: Wed Jan 14 10:11:15 2015
InstallationDate: Installed on 2014-08-01 (165 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
SourcePackage: lxc
UpgradeStatus: Upgraded to utopic on 2014-09-11 (125 days ago)
defaults.conf:
 lxc.network.type = veth
 lxc.network.link = lxcbr0
 lxc.network.flags = up
 lxc.network.hwaddr = 00:16:3e:xx:xx:xx

[Serge Hallyn (serge-hallyn)]

Thanks, that definately should be fixed if possible.

 status: triaged
 importance: high