How Do I Get Into a Docker Container’s Shell?

To access a Docker container’s shell, you can use the docker exec or docker attach commands. Below are the common methods:

1. Using docker exec

The docker exec command is the most common way to open a shell session in a running Docker container. It allows you to execute a command (e.g., starting a shell) inside a container.

Steps:

1. List Running Containers:

   docker ps
   

   • This shows all running containers along with their CONTAINER ID and NAMES.
2. Access the Container’s Shell: Use the docker exec command to start a shell session.
   • For a Bash shell:

     docker exec -it <container_name_or_id> /bin/bash
     

   • For a Shell (sh), if Bash is unavailable:

     docker exec -it <container_name_or_id> /bin/sh
     

   • Replace <container_name_or_id> with the container’s name or ID.
3. Exit the Shell: Type exit to leave the container shell.

2. Using docker attach

The docker attach command allows you to interact with the container’s main process.

Steps:

1. List Running Containers:

   docker ps
   

2. Attach to the Container:

   docker attach <container_name_or_id>
   

3. Detach from the Container:
   • Press Ctrl + P and then Ctrl + Q to detach without stopping the container.
   • Alternatively, use exit to detach and stop the container.

3. Using docker exec with a New Terminal

If you want a new terminal session (especially useful for debugging):

docker exec -it <container_name_or_id> /bin/bash

4. For Stopped Containers

If the container is not running, you’ll need to start it first:

docker start <container_name_or_id>

Then, use one of the above methods to access the shell.

Common Errors

1. Bash Not Found:
   • Some minimal Docker images (like Alpine Linux) don’t have Bash installed. In such cases, use:

     docker exec -it <container_name_or_id> /bin/sh
     

2. Permission Denied:
   • Ensure you have appropriate permissions to run Docker commands. If necessary, prefix the commands with sudo.

Tips

• Use docker ps -a to list all containers, including stopped ones.
• If you’re unsure about the container’s shell, try both /bin/bash and /bin/sh.