Running Docker Containers as Non-Root Users with Sudo Access

Docker is a popular containerization platform that allows developers to package applications and their dependencies into containers. These containers are isolated environments that provide consistent behavior across various computing environments. By default, Docker containers run as the root user inside the container, but for security reasons, it’s often recommended to run containers with non-root users.

Why Run Containers as Non-Root Users?

Running a container as a non-root user reduces potential security risks. If an attacker compromises a container running as root, they could gain elevated privileges on the host system or other containers. By restricting permissions within a container, you limit what can be done if it’s compromised.

Understanding Sudo Access

sudo, short for "superuser do," allows permitted users to execute commands with elevated privileges. Within Docker containers, adding sudo capabilities enables non-root users to perform administrative tasks when necessary.

Setting Up Non-Root Containers with Sudo Access in Docker

To achieve this setup, you will need to:

Update package lists.
Install the sudo package.
Add a new user and grant them sudo access without a password prompt.

Here’s how you can modify your Dockerfile to include these steps:

FROM ubuntu:12.04

# Step 1: Update the package list
RUN apt-get update && \
    # Step 2: Install sudo
    apt-get install -y sudo

# Step 3: Create a new user and set permissions
RUN useradd -m docker && \
    echo "docker:docker" | chpasswd && \
    adduser docker sudo

# Allow the docker user to execute commands with sudo without password prompt
RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers

# Switch to the newly created non-root user
USER docker

# Set the default command to be executed when starting the container
CMD ["/bin/bash"]

Building and Running Your Docker Image

Build your image:
```
docker build -t my_non_root_image .
```
Run a container using this image:
```
docker run -it my_non_root_image
```

Inside the container, you can now use sudo to execute commands with elevated privileges without needing to enter a password.

Troubleshooting

Package Not Found: If you encounter an error saying "Unable to locate package sudo," ensure that your package list is updated by running apt-get update.
Existing Containers: If the issue arises in an already running container, you can connect as root and modify it:
```
docker exec -ti -u root <container_id> /bin/bash
```
From there, repeat the steps to install sudo and configure user permissions.

Committing Changes

After making changes to a running container, consider saving your modifications by committing them to an image:

docker commit <container_id> my_new_image_name

This step ensures that future containers launched from this updated image will include the changes you made.

Conclusion

Running Docker containers as non-root users enhances security and minimizes risk. By following these steps, you can configure your Docker setup to allow non-root users sudo access while maintaining a secure container environment.