Find the container of a process, and the processes of a container

container-process-mapping.md

How to find containers of processes and vice versa

This is about Linux Containers, managed with LXC or LXD.

What are the processes of a container?

# lxc-info -p -n CONTAINERNAME                  # -p or --pid displays init's PID
PID:            27149
# pstree -p 27149
systemd(27149)─┬─agetty(27502)
               ├─agetty(27503)
               ├─agetty(27504)
               ├─agetty(27505)
               ├─agetty(27507)
               ├─cron(27339)
               ├─dhclient(27472)
               ├─rsyslogd(27334)─┬─{in:imklog}(27359)
               │                 ├─{in:imuxsock}(27358)
               │                 └─{rs:main Q:Reg}(27360)
               ├─sshd(27495)
               └─systemd-journal(27263)

A process added for example with lxc-console or lxc-execute also appears in the list.

What are the namespaces of a container?

# ls -l /proc/PID_OF_INIT/ns
total 0
lrwxrwxrwx 1 root root 0 Feb 28 14:11 cgroup -> cgroup:[4026532507]
lrwxrwxrwx 1 root root 0 Feb 28 14:11 ipc -> ipc:[4026532447]
lrwxrwxrwx 1 root root 0 Feb 28 14:11 mnt -> mnt:[4026532379]
lrwxrwxrwx 1 root root 0 Feb 28 14:11 net -> net:[4026532450]
lrwxrwxrwx 1 root root 0 Feb 28 14:11 pid -> pid:[4026532448]
lrwxrwxrwx 1 root root 0 Feb 28 14:13 user -> user:[4026531837]
lrwxrwxrwx 1 root root 0 Feb 28 14:11 uts -> uts:[4026532446]

ps -o mntns etc should also display namespaces, but it only shows a dash.

Which is the container of a given process?

List its namespaces and compare them with the namespaces of all containers.

To be continued