How to Enter a Docker Container Already Running with a New TTY

TLDR

To enter a running Docker container with a new TTY session, use the docker exec command with the -it flags. This allows you to interact with the container's shell for debugging or administrative tasks.

When working with Docker, you may need to interact with a running container to debug issues, inspect files, or perform administrative tasks. This guide will show you how to attach to a running container with a new TTY session.

Prerequisites

Before proceeding, make sure you have:

Docker installed on your system.
A running Docker container you want to access.
Appropriate permissions to interact with Docker.

Step 1: List Running Containers

To identify the container you want to access, list all running containers using the following command:

docker ps

This will display a list of running containers, including their IDs, names, and other details. For example:

CONTAINER ID   IMAGE          COMMAND                  CREATED        STATUS       PORTS                    NAMES
abc123         nginx:latest   "nginx -g 'daemon of…"   2 hours ago   Up 2 hours   0.0.0.0:8080->80/tcp     my-nginx

Note the CONTAINER ID or NAMES of the container you want to access.

Step 2: Attach to the Container with a New TTY

To open a new TTY session in the running container, use the docker exec command with the -it flags:

docker exec -it <container-name-or-id> /bin/bash

Replace <container-name-or-id> with the CONTAINER ID or NAMES from the previous step. For example:

docker exec -it my-nginx /bin/bash

This command starts a new interactive shell session (/bin/bash) inside the container.

Example Output

root@abc123:/#

You are now inside the container and can run commands as if you were logged into a separate machine.

Step 3: Use an Alternative Shell (if Necessary)

Not all containers include /bin/bash. If the container uses a minimal base image, you may need to use /bin/sh instead:

docker exec -it <container-name-or-id> /bin/sh

For example:

docker exec -it my-nginx /bin/sh

Step 4: Exit the Container

To exit the container's shell session, type:

exit

This will close the TTY session and return you to your host machine's terminal.

Additional Tips

Inspect Container Logs: Use docker logs <container-name-or-id> to view logs if you don't need an interactive session.
Attach vs. Exec: The docker attach command connects to the container's main process, while docker exec starts a new process inside the container.
Use Docker Compose: If you're using Docker Compose, you can access a container with:
```
docker-compose exec <service-name> /bin/bash
```