Quick-Hit: Am I Inside A Docker Container?

If you don’t know, here’s an easy way to find out…

cat /proc/self/cgroup

If you see “/docker/{hash}” following one of the outputs then yes, yes you are. A non-Docker system looks like the following:

11:freezer:/
10:perf_event:/
9:pids:/user.slice
8:cpuset:/
7:memory:/user.slice
6:net_cls,net_prio:/
5:blkio:/user.slice
4:cpu,cpuacct:/user.slice
3:hugetlib:/
2:devices:/user.slice
1:name=systemd:/user.slice/{etc}

A Docker system looks like this:

11:freezer:/
10:perf_event:/
9:pids:/user.slice
8:cpuset:/
7:memory:/user.slice
6:net_cls,net_prio:/
5:blkio:/user.slice
4:cpu:/docker/{hash}
3:hugetlib:/
2:devices:/docker/{hash}
1:name=systemd:/user.slice/{etc}

Good hunting!