How to add users to Docker container?

Question

I have a docker container with some processes (uwsgi and celery) running inside. I want to create a celery user and a uwsgi user for these processes as well as a worker group that they will both belong to, in order to assign permissions. I tried adding `RUN adduser uwsgi` and `RUN adduser celery` to my Dockerfile, but this is causing problems, since these commands prompt for input (I've posted the responses from the build below). What is the best way to add users to a Docker container so as to set permissions for workers running in the container? My Docker image is built from the official Ubuntu14.04 base. Here is the output from the Dockerfile when the adduser commands are run: ``` Adding user `uwsgi' ... Adding new group `uwsgi' (1000) ... Adding new user `uwsgi' (1000) with group `uwsgi' ... Creating home directory `/home/uwsgi' ... Copying files from `/etc/skel' ... [91mEnter new UNIX password: Retype new UNIX password: [0m [91mpasswd: Authentication token manipulation error passw…

Accepted Answer

The trick is to use `useradd` instead of its interactive wrapper `adduser`. I usually create users with:

```
RUN useradd -ms /bin/bash newuser
```

which creates a home directory for the user and ensures that bash is the default shell.

You can then add:

```
USER newuser
WORKDIR /home/newuser
```

to your dockerfile. Every command afterwards as well as interactive sessions will be executed as user `newuser`:

```
docker run -t -i image
newuser@131b7ad86360:~$
```

You might have to give `newuser` the permissions to execute the programs you intend to run before invoking the user command.

Using non-privileged users inside containers is a good idea for security reasons. It also has a few drawbacks. Most importantly, people deriving images from your image will have to switch back to root before they can execute commands with superuser privileges.

How to add users to Docker container?

Solution

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