If you’re using LXC, you might have noticed that there was a 0.8.0 release lately, finally, after two release candidates, one of which was never really released. Do you expect everything would go well with it? Hah!
Well, you might remember that over time I found that the way that you’re supposed to mount directories in the configuration files changed, from using the path to use as root, to the default root path used by LXC, and every time that happened, no error message was issued that you were trying to mount directories outside of the tree that they are running.
Last time the problem I hit was that if you try to mount a volume instead of a path, LXC expected you to use as a base path the full realpath, which in the case of LVM volumes is quite hard to know by heart. Yes you can look it up, but it’s a bit of a bother. So I ended up patching LXC to allow using the old format, based on the path LXC mounts it to (/usr/lib/lxc/rootfs). With the new release, this changed again, and the path you’re supposed to use is /var/lib/lxc/${container}/rootfs — again, it’s a change in a micro bump (rc2 to final) which is not documented…. sigh. This would be enough to irk me, but there is more.
The new version also seem to have a bad interaction with the kernel on stopping of a container — the virtual ethernet device (veth pair) is not cleared up properly, and it causes the process to stall, with something insisting to call the kernel and failing. The result is a not happy Diego.
Without even having to add the fact that the interactions between LXC and SystemD are not clear yet – with the maintainers of the two projects trying to sort out the differences between them, at least I don’t have to care about it anytime soon – this should be enough to make it explicit that LXC is not ready for prime time so please don’t ask.
On a different, interesting note, the vulnerability publicized today that can bypass KERNEXEC? Well, unless you disable the net_admin capability in your containers (which also mean you can’t set the network parameters, or use iptables), a root user within a container could leverage that particular vulnerability.. which is one extremely good reason not to have untrusted users having root on your containers.
Oh well, time to wait for the next release and see if they can fix a few more issues.