Jenkins Docker Plugin
External
- https://plugins.jenkins.io/docker-commons https://wiki.jenkins.io/display/JENKINS/Docker+Commons+Plugin
- https://plugins.jenkins.io/docker-plugin https://wiki.jenkins.io/display/JENKINS/Docker+Plugin
Internal
Overview
Docker plugin (ID docker-plugin) enables Jenkins to use a Docker server to provision build agents, run a single build and then tear down the agent. Optionally, the container can be committed after build. Docker plugin depends on Docker
ID: docker-commons
Concepts
Docker Agent
Jenkins can interact with agents executing as containers within a Docker instance. The agent containers must be based on one of the following base images:
jenkins/ssh-slave
The image comes with sshd and a JDK. The Jenkins master will use ssh to connect into the agent's sshd. A SSH key based on unique Jenkins master instance identity can be injected in container on startup, obviating the need for password.
jenkins/jnlp-slave
The image comes with JDK. Jenkins master URL has to be reachable from the agent's container. The container will be configured automatically with the agent's name and secret. No special configuration of the container is needed.
jenkins/slave
An "attached" agent.
Installation
Plugin Installation
Manually from the UI or:
/usr/local/bin/install-plugins.sh docker-plugin
After the plugin is installed, a new configuration category shows up: Manage Jenkins -> Configure System -> Cloud.
Jenkins Server Configuration
Jenkins -> Manage Jenkins -> Configure System -> Cloud -> Add a new cloud -> Docker
Name
docker
The name should be something suggestive that indicates what docker server is actually used.
Docker Host URI
It is the URI to the Docker Host. May be left blank to use the default value defined by DOCKER_HOST environment variable. A typical value is unix:///var/run/docker.sock or tcp://127.0.0.1:2376.
Using Unix-domain Sockets for Jenkins Running as a Container
Note that if Jenkins itself runs as a Docker container on the same Docker server to be used for agent provisioning, and wants to use a Unix-doman socket for access, it won't access by default to unix:///var/run/docker.sock of the Docker host. Access can be enabled by starting the Jenkins container as follows:
docker run ... --mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock ... <jenkins-image>
This command maps the Docker-host level /var/run/docker.sock into the container, and sets appropriate permissions on the container-level /var/run/docker.sock so Jenkins can access it.
For concepts behind bind mounts, see Docker Bind Mounts. Also, the Docker host-level user mapped to the Jenkins process must be added to the "docker" group, so it has access to the Unix socket. For more details see Non-root Management Access for Docker.
Server credentials
Unix-domain socket do not require credentials, though the socket must have proper access permissions.
Test Connection
Useful for debugging. A successful connection to the Docker server should return something like:
Version = 18.03.0-ce, API Version = 1.37
Enabled
Must be specifically enabled. Not by default.
Docker Agent Templates
This section configures the images to be launched as agents. Each agent docker image is associated with a Jenkins label. The image must be available in an accessible registry.
Docker Server Setup
Configuration
The agent images need to be created and accessible to the Jenkins server.