How do I get into a Docker container?

Question

I'm getting started working with Docker. I'm using the WordPress base image and docker-compose.

I'm trying to ssh into one of the containers to inspect the files/directories that were created during the initial build. I tried to run docker-compose run containername ls -la, but that didn't do anything. Even if it did, I'd rather have a console where I can traverse the directory structure, rather than run a single command. What is the right way to do this with Docker?

Answer 1

If you have Docker installed with Kitematic, you can use the GUI. Open Kitematic from the Docker icon and in the Kitematic window select your container, and then click on the exec icon.

You can see the container log and lots of container information (in settings tab) in this GUI too.

Answer 2

In some cases your image can be Alpine-based. In this case it will throw:

OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused "exec: \"bash\": executable file not found in $PATH": unknown

Because /bin/bash doesn't exist. Instead of this you should use:

docker exec -it 9f7d99aa6625 ash

or

docker exec -it 9f7d99aa6625 sh

Answer 3

Notice: this answer promotes a tool I've written.

I've created a containerized SSH server that you can 'stick' to any running container. This way you can create compositions with every container. The only requirement is that the container has Bash.

The following example would start an SSH server attached to a container with name 'my-container'.

docker run -d -p 2222:22 \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e CONTAINER=my-container -e AUTH_MECHANISM=noAuth \
  jeroenpeeters/docker-ssh

ssh localhost -p 2222

When you connect to this SSH service (with your SSH client of choice) a Bash session will be started in the container with name 'my-container'.

For more pointers and documentation see: https://github.com/jeroenpeeters/docker-ssh

Answer 4

If the container has already exited (maybe due to some error), you can do

$ docker run --rm -it --entrypoint /bin/ash image_name

or

$ docker run --rm -it --entrypoint /bin/sh image_name

or

$ docker run --rm -it --entrypoint /bin/bash image_name

to create a new container and get a shell into it. Since you specified --rm, the container would be deleted when you exit the shell.

Answer 5

If you're using Docker on Windows and want to get shell access to a container, use this:

winpty docker exec -it <container_id> sh

Most likely, you already have Git Bash installed. If you don't, make sure to install it.

Answer 6

docker attach will let you connect to your Docker container, but this isn't really the same thing as ssh. If your container is running a webserver, for example, docker attach will probably connect you to the stdout of the web server process. It won't necessarily give you a shell.

The docker exec command is probably what you are looking for; this will let you run arbitrary commands inside an existing container. For example:

docker exec -it <mycontainer> bash

Of course, whatever command you are running must exist in the container filesystem.

In the above command <mycontainer> is the name or ID of the target container. It doesn't matter whether or not you're using docker compose; just run docker ps and use either the ID (a hexadecimal string displayed in the first column) or the name (displayed in the final column). E.g., given:

$ docker ps
d2d4a89aaee9        larsks/mini-httpd   "mini_httpd -d /cont   7 days ago          Up 7 days                               web                 

I can run:

$ docker exec -it web ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
18: eth0: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 02:42:ac:11:00:03 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.3/16 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe11:3/64 scope link 
       valid_lft forever preferred_lft forever

I could accomplish the same thing by running:

$ docker exec -it d2d4a89aaee9 ip addr

Similarly, I could start a shell in the container;

$ docker exec -it web sh
/ # echo This is inside the container.
This is inside the container.
/ # exit
$