How to setup an ssh server within a docker container

In this post I will walk you through my process of setting up ssh access to your docker container.

Why run an ssh server within a container in the first place?

The major reason why you might want to do this is for testing purposes, perhaps you are testing infrastructure automation or provisioning with something like ansible which requires ssh access to the target machine, you'd want to test this in a safe environment before going live.

• This article assumes you have docker installed on your machine if not you can refer to this page to get it installed here

The Dockerfile!

FROM ubuntu:latest

RUN apt update && apt install  openssh-server sudo -y

RUN useradd -rm -d /home/ubuntu -s /bin/bash -g root -G sudo -u 1000 test 

RUN  echo 'test:test' | chpasswd

RUN service ssh start

EXPOSE 22

CMD ["/usr/sbin/sshd","-D"]

Here I am using ubuntu as the base image for the container, then on line 2 i install open-ssh server and sudo.

Sudo?

By default docker does not have sudo installed , hence the need to install it along with the open ssh server

On line 3 i create a user called test and add it to the sudo group

echo 'test:test' | chpasswd sets the password for the user test to test

Line 5 starts the ssh service and line 6 tells docker the container listens on port 22 ( which is the default for ssh) and finally i start the ssh daemon.

Building the image

To build the image run docker build -t IMAGE_NAME . , once that's done you can run the image using docker run IMAGE_NAME -p 22:22. finally you can connect to the container using the user you created , in this case it will be test so ssh test@ip_address enter your password in the prompt and your all setup

The original Dockerfile can be found on my github here