[linux] How to add users to Docker container?

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
passwd: password unchanged
[0m 
[91mUse of uninitialized value $answer in chop at /usr/sbin/adduser line 563.
[0m 
[91mUse of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 564.
[0m 
Try again? [y/N] 
Changing the user information for uwsgi
Enter the new value, or press ENTER for the default
    Full Name []: 
Room Number []:     Work Phone []:  Home Phone []:  Other []: 
[91mUse of uninitialized value $answer in chop at /usr/sbin/adduser line 589.
[0m 
[91mUse of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 590.
[0m 
Is the information correct? [Y/n] 
---> 258f2f2f13df 
Removing intermediate container 59948863162a 
Step 5 : RUN adduser celery 
---> Running in be06f1e20f64 
Adding user `celery' ...
Adding new group `celery' (1001) ... 
Adding new user `celery' (1001) with group `celery' ... 
Creating home directory `/home/celery' ...
Copying files from `/etc/skel' ... 
[91mEnter new UNIX password: Retype new UNIX password: [0m 
[91mpasswd: Authentication token manipulation error
passwd: password unchanged
[0m 
[91mUse of uninitialized value $answer in chop at /usr/sbin/adduser line 563.
[0m 
[91mUse of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 564.
[0m 
Try again? [y/N] 
Changing the user information for celery
Enter the new value, or press ENTER for the default
    Full Name []:   Room Number []:     Work Phone []: 
Home Phone []:  Other []: 
[91mUse of uninitialized value $answer in chop at /usr/sbin/adduser line 589.
[0m 
[91mUse of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 590.
[0m 
Is the information correct? [Y/n] 

To avoid the interactive questions by adduser, you can call it with these parameters:

RUN adduser --disabled-password --gecos '' newuser

The --gecos parameter is used to set the additional information. In this case it is just empty.

On systems with busybox (like Alpine), use

RUN adduser -D -g '' newuser

See busybox adduser

Everyone has their personal favorite, and this is mine:

RUN useradd --user-group --system --create-home --no-log-init app
USER app

Reference: man useradd

The RUN line will add the user and group app:

root@ef3e54b60048:/# id app
uid=999(app) gid=999(app) groups=999(app)

Use a more specific name than app if the image is to be reused as a base image. As an aside, include --shell /bin/bash if you really need.

Partial credit: answer by Ryan M

Adding user in docker and running your app under that user is very good practice for security point of view. To do that I would recommend below steps:

FROM node:10-alpine

# Copy source to container
RUN mkdir -p /usr/app/src

# Copy source code
COPY src /usr/app/src
COPY package.json /usr/app
COPY package-lock.json /usr/app

WORKDIR /usr/app

# Running npm install for production purpose will not run dev dependencies.
RUN npm install -only=production    

# Create a user group 'xyzgroup'
RUN addgroup -S xyzgroup

# Create a user 'appuser' under 'xyzgroup'
RUN adduser -S -D -h /usr/app/src appuser xyzgroup

# Chown all the files to the app user.
RUN chown -R appuser:xyzgroup /usr/app

# Switch to 'appuser'
USER appuser

# Open the mapped port
EXPOSE 3000

# Start the process
CMD ["npm", "start"]

Above steps is a full example of the copying NodeJS project files, creating a user group and user, assigning permissions to the user for the project folder, switching to the newly created user and running the app under that user.

Alternatively you can do like this.

RUN addgroup demo && adduser -DH -G demo demo

First command creates group called demo. Second command creates demo user and adds him to previously created demo group.

Flags stands for:

-G Group
-D Don't assign password
-H Don't create home directory

You can imitate open source Dockerfile, for example:

Node: node12-github

RUN groupadd --gid 1000 node \
    && useradd --uid 1000 --gid node --shell /bin/bash --create-home node

superset: superset-github

RUN useradd --user-group --create-home --no-log-init --shell /bin/bash 
    superset

I think it's a good way to follow open source.

Add this line to your Dockerfile (You can run any linux command this way)

RUN useradd -ms /bin/bash yourNewUserName

Ubuntu

Try the following lines in Dockerfile:

RUN useradd -rm -d /home/ubuntu -s /bin/bash -g root -G sudo -u 1001 ubuntu
USER ubuntu
WORKDIR /home/ubuntu

useradd options (see: man useradd):

• -r, --system Create a system account. ^{see: Implications creating system accounts}
• -m, --create-home Create the user's home directory.
• -d, --home-dir HOME_DIR Home directory of the new account.
• -s, --shell SHELL Login shell of the new account.
• -g, --gid GROUP Name or ID of the primary group.
• -G, --groups GROUPS List of supplementary groups.
• -u, --uid UID Specify user ID. ^{see: Understanding how uid and gid work in Docker containers}
• -p, --password PASSWORD Encrypted password of the new account (e.g. ubuntu).

Setting default user's password

To set the user password, add -p "$(openssl passwd -1 ubuntu)" to useradd command.

Alternatively add the following lines to your Dockerfile:

SHELL ["/bin/bash", "-o", "pipefail", "-c"]
RUN echo 'ubuntu:ubuntu' | chpasswd

The first shell instruction is to make sure that -o pipefail option is enabled before RUN with a pipe in it. Read more: Hadolint: Linting your Dockerfile.