Get shell in running Docker container

This has saved me more times than I can count, having the ability to debug a running container the way you would in a “normal” VM.

First, see which containers are running;

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  [...] NAMES
925cc10d55df        66cc85c3f275        "gitlab-runner-ser..."   [...] runner-f500bed1-project-3888560-concurrent-0-mysql-0-wait-for-service
0ab431ea0bcf        3e3878acd190        "docker-entrypoint..."   [...] runner-f500bed1-project-3888560-concurrent-0-mysql-0
4d9de6c0fba1        nginx:alpine        "nginx -g 'daemon ..."   [...] nginx-container

To get a shell (Bash) on a container of choice, run this;

$ docker exec -i -t nginx-container /bin/bash

The nginx-container determines which container you want to enter, it’s the name in the last column of the docker ps output.

Alternatively, use the container ID;

$ docker exec -i -t 4d9de6c0fba1 /bin/bash

Don’t use docker attach, as that’ll give you funky results if the initial command that’s started in a Docker container is something like MongoDB or Redis, the instance will be killed.