We tried running Docker inside a microVM. It failed before the first container even started. The error wasn’t helpful: cgroup mountpoint does not exist On a normal EC2 instance, Docker just works. Same binary, same commands. Here, it couldn’t even initialize. This wasn’t a Docker issue. It wasn’t a kernel bug either. It was something more subtle: we were relying on parts of Linux that weren’t there anymore . The part nobody thinks about On a normal Linux system, you don’t start from zero. By the time you SSH into a machine and type docker run , a lot has already happened. You SSH in, run Docker, and it works. If it doesn’t, it’s usually your fault , a wrong command or wrong config. Here, it didn’t feel like our mistake. It felt like something fundamental was missing. So instead of poking Docker, we started looking at the system itself. The error mentioned cgroups. So we checked: ls /sys/fs/cgroup Nothing useful. Then: mount | grep cgroup Nothing. That’s when it clicked, this wasn’t misconfigured.…