Support restarting LXD-based containers

[JohnstonJ]

As per:

https://github.com/liske/needrestart/blob/f9cd0d3169be4eda7cf84357072ff935c81e9b5d/README.Cont.md

it is stated that there is container support for restarting containers. Notably absent is LXD: https://linuxcontainers.org/lxd/

If an LXD container is in use, the command for restarting it would be:

lxc restart <container>

[liske]

LXD does not implement containers itself but uses LXC in the background. So there is no need to support LXD explicitly, isn't it? Do you have a LXD environment available and did you give the most recent needrestart a try?

[JohnstonJ]

Sort of. LXD uses liblxc but none of the old LXC command-line tools. So for example, lxc-stop is not even on my system. So according to the needrestart readme, it can't work since that tool isn't installed.

Even if it was installed, I am not sure if this is advisable or supportable or if it even works. I think the LXD daemon assumes it has full control over the state of the containers under its control. See for example the container state management here https://github.com/lxc/lxd/blob/8d58e07c63808b0f13bdf8777fcfe7edcdb352f0/lxd/container_state.go which uses LXD-specific configuration variables, LXD-specific logging, and so forth. lxc-stop would bypass all that and so that sounds fragile to me.

That said, I couldn't find any documentation/guidance on whether this is actually not supported or not. (They do recommend not mixing LXC and LXD in other ways, e.g. lxc/incus@33bc6b9 ).

[liske]

Did you try to run needrestart while running a container (under control of LXD) using a outdated library? Did needrestart already detect the container? If so, it might become hard to differ between pure LXC and LXD containers...

Could you please provide the content /proc/<pid>/cgroup of a process within a LXC container?

[lenucksi]

Here are the contents of a process within a LXD container that needrestart wants to restart.

container is the name of the container the process runs in.

cat /proc/6992/cgroup
11:blkio:/lxc/container/system.slice/avahi-daemon.service
10:memory:/lxc/container/system.slice/avahi-daemon.service
9:pids:/lxc/container/system.slice/avahi-daemon.service
8:hugetlb:/lxc/container
7:perf_event:/lxc/container
6:cpuset:/lxc/container
5:net_cls,net_prio:/lxc/container
4:freezer:/lxc/container
3:cpu,cpuacct:/lxc/container/system.slice/avahi-daemon.service
2:devices:/lxc/container/system.slice/avahi-daemon.service
1:name=systemd:/lxc/container/system.slice/avahi-daemon.service