How to determine if a process runs inside lxc/Docker?

Question

Is there any way to determine if a process (script) runs inside an lxc container (~ Docker runtime)? I know that some programs are able to detect whether they run inside a v

Answer 1

In a docker container, entries /proc/self/cgroup are mounted to cgroups on the host.

e.g. in a container

# awk -F: '/cpuset/' /proc/self/cgroup
3:cpuset:/docker/22bd0c154fb4e0d1b6c748faf1f1a12116acc21ce287618a115ad2bea41256b3

whereas, the same on the host

$ awk -F: '/cpuset/' /proc/self/cgroup
3:cpuset:/

Using something in the shell for a low profile test

is_running_in_container() {
  awk -F: '/cpuset/ && $3 ~ /^\/$/{ c=1 } END { exit c }' /proc/self/cgroup
}

if is_running_in_container; then
  echo "Aye!! I'm in a container"
else 
  echo "Nay!! I'm not in a container"
fi