How to add users to Docker container?

Adding users to Docker containers can be achieved through several methods, depending on your specific requirements such as the need for persistent user data and permission levels. Below, I will detail several common approaches:

Method 1: Using the USER command in Dockerfile

If you know in advance which user to add during Docker image construction, you can add the user and switch to it within the Dockerfile. This approach is suitable for scenarios where applications need to run as a non-root user. Here is an example:

dockerfile
# Use the official Ubuntu image
FROM ubuntu:20.04

# Update packages and install sudo (for demonstration)
RUN apt-get update && apt-get install -y sudo

# Add new user `myuser`
RUN useradd -m myuser

# Set password for new user `myuser` (it is recommended to use a more secure method, such as key-based authentication)
RUN echo 'myuser:password' | chpasswd

# Switch to new user
USER myuser

# Continue with other Dockerfile commands...

Method 2: Adding users at runtime

If you need to add a user to an already running container, you can do so by entering the container and using user management commands. Here are the steps:

1. First, use the docker exec command to enter the running container:

   bash
   

docker exec -it bash

shell

2. Within the container, you can use the `useradd` command to add a user:

   ```bash
useradd -m newuser

1. If needed, you can set the user's password:

   bash
   

passwd newuser

shell

4. Exit the container after completion.

Users remain after container restart, but they are lost if the container is deleted.

### Method 3: Using Docker Compose

If you manage containers using Docker Compose, you can add users in the `docker-compose.yml` file using a method similar to Dockerfile:

```yaml
version: '3.8'
services:
  app:
    image: ubuntu:20.04
    command: sleep infinity
    user: "1000:1000"

Here, user: "1000:1000" specifies the user and group ID under which the container command should run. This approach is suitable if you already know the user ID and group ID and do not need to create specific user accounts within the container.

Summary

Depending on your specific use cases and requirements, you can choose to add users during image construction via Dockerfile, dynamically add users at runtime, or specify the running user via Docker Compose. Each method has its appropriate scenarios, and you should select the most suitable one based on your situation.