#StackBounty: #linux #docker Attaching process from one Docker container to another

Bounty: 50

I’m trying to reveal technical detail of CircleCI feature implementation which calls Multi-Image.

They allow specifying multiple images this way:

  test-job:
    docker:
    - image: nginx
    - image: circleci/mariadb:10.2

Then they run build in the Docker container based on the first image (nginx in this case). And if you connect to nginx container you may see mysqld process there too:

  PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND
...
    7     0 999      S    2518m   2%  31   0% mysqld
...

It seems like they attach a process from the mariadb container to the nginx container.

How it even possible? I do not see such ability in docker.

I thought it works like multiple containers in the same Kubernetes pod but it is not. You do not see processes in one container from others on the same pod.

Any ideas?


Get this bounty!!!

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