Connect to docker container as user other than root

BY default when you run

docker run -it [myimage]

OR

docker attach [mycontainer]

you connect to the terminal as root user, but I would like to connect as a different user. Is this possible?

Solution 1:

For docker run:

Simply add the option --user <user> to change to another user when you start the docker container.

docker run -it --user nobody busybox

For docker attach or docker exec:

Since the command is used to attach/execute into the existing process, therefore it uses the current user there directly.

docker run -it busybox  # CTRL-P/Q to quit
docker attach <container id>  # then you have root user
/ # id
uid=0(root) gid=0(root) groups=10(wheel)

docker run -it --user nobody busybox # CTRL-P/Q to quit
docker attach <container id>  
/ $ id
uid=99(nobody) gid=99(nogroup)

If you really want to attach to the user you want to have, then

1. start with that user run --user <user> or mention it in your Dockerfile using USER
2. change the user using `su

Solution 2:

You can run a shell in a running docker container using a command like:

docker exec -it --user root <container id> /bin/bash

Solution 3:

As an updated answer from 2020. --user , -u option is Username or UID (format: <name|uid>[:<group|gid>]).

Then, it works for me like this,

docker exec -it -u root:root container /bin/bash

Reference: https://docs.docker.com/engine/reference/commandline/exec/

Solution 4:

You can specify USER in the Dockerfile. All subsequent actions will be performed using that account. You can specify USER one line before the CMD or ENTRYPOINT if you only want to use that user when launching a container (and not when building the image). When you start a container from the resulting image, you will attach as the specified user.