I was trying to set up the docker plugin

https://wiki.jenkins-ci.org/display/JENKINS/Docker+Plugin

to use the ready-made slave everga

https://registry.hub.docker.com/u/evarga/jenkins-slave

According to the documentation it should work smoothly but for me it does not work how it is.

In the docker file it defines the user jenkins:jenkins. However trying to connect from Jenkins to your everga container image using username
and password won't work: I needed to create an ssh key pair and modify the /etc/ssh/ssh_config file to point to the private key and /etc/ssh/sshd_config to point to the authorized_key file.