Setup an openssh-server in a docker container

This is mainly used for testing only. 

First create a Dockerfile. I am using ubuntu:20.04 image for this

$ cat >> Dockerfile <<EOF

FROM ubuntu:20.04

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

RUN useradd myuser && echo "myuser:123456" | chpasswd && echo "root:123456" | chpasswd && mkdir /run/sshd

EXPOSE 22

CMD /usr/sbin/sshd -D

EOF

Then, build the image

$ docker build -t mysshimage .

Finally, run a container based on the image, and ssh into it. Use 123456 as password.

$ docker run -dit -p 1022:22 mysshimage

$ ssh myuser@localhost -p 1022 

To be a root user, just use su - command once you are logged in as myuser.