Docker: Ssh Access Directly into Container

SSH directly into a docker container

You can drop directly into a running container with:

$ docker exec -it myContainer /bin/bash

You can get a shell on a container that is not running with:

$ docker run -it myContainer /bin/bash

This is the preferred method of getting a shell on a container. Running an SSH server is considered not a good practice and, although there are some use cases out there, should be avoided when possible.

docker: SSH access directly into container

Let's remember however that having ssh support in a container is typically an anti-pattern (unless it's your container only 'concern' but then what would be the point of being able to ssh in. Refer to http://techblog.constantcontact.com/devops/a-tale-of-three-docker-anti-patterns/ for information about that anti-pattern

How to SSH into Docker?

Firstly you need to install a SSH server in the images you wish to ssh-into. You can use a base image for all your container with the ssh server installed.
Then you only have to run each container mapping the ssh port (default 22) to one to the host's ports (Remote Server in your image), using -p <hostPort>:<containerPort>. i.e:

docker run -p 52022:22 container1 
docker run -p 53022:22 container2

Then, if ports 52022 and 53022 of host's are accessible from outside, you can directly ssh to the containers using the ip of the host (Remote Server) specifying the port in ssh with -p <port>. I.e.:

ssh -p 52022 myuser@RemoteServer --> SSH to container1

ssh -p 53022 myuser@RemoteServer --> SSH to container2

Using SSH keys inside docker container

Turns out when using Ubuntu, the ssh_config isn't correct. You need to add

RUN  echo "    IdentityFile ~/.ssh/id_rsa" >> /etc/ssh/ssh_config

to your Dockerfile in order to get it to recognize your ssh key.

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