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

Check for all the solutions above in Python:

import os

def in_container():
    proc_1 = r'/proc/1/sched'

    if os.path.exists(proc_1):
        with open(proc_1, 'r') as fp:
            out = fp.read()
    else:
        out = ''

    checks = [
        'docker' in out,
        '/lxc/' in out,
        out.split(' ')[0] not in ('systemd', 'init',),
        os.path.exists('./dockerenv'),
        os.path.exists('/.dockerinit'),
        os.getenv('container') is not None
    ]
    return any(checks)


if __name__ == '__main__':
    print(in_container())

Proof of concept:

$ docker run --rm -it --mount type=bind,source=${PWD}/incontainer.py,target=/tmp/script.py python:3 python /tmp/script.py
True