persist_in_docker_volumes.md

Persist Data In Docker Volumes

Docker offers Docker volumes to separate your precious data from containers. You can remove and replace your container without losing any data.

Firstly, create a volume:

$ docker volume create --name jenkins_data

Note: The volumes name is jenkins_data. You can also check with docker volume ls.

Secondly, start Jenkins and mount the newly created volume:

$ docker run -d \
    -p 8090:8080 \
    -v jenkins_data:/jenkins \
    --name jenkins \
    blacklabelops/jenkins

Note: Must be always mounted at /jenkins; the container's fixed data directory.

##You want to check what's written inside your volume?

You can check the volume's content from your running Jenkins:

$ docker exec -it jenkins bash
... you operations here....

Connects and runs bash inside your running Jenkins. You will be directed to the directory /jenkins because it's defined as the container's workfolder.

You can check with a separate container:

$ docker run -it --rm \
    -v jenkins_data:/jenkins \
    blacklabelops/alpine bash
$ cd /jenkins
... you operations here....

This container will mount the volume regardless if your Jenkins is still running! Please bear this in mind. Especially backups can be inconsistent when Jenkins is still running.

Read Only Volume

Docker's default for the volume parameter -v is read and write access. There's also a read-only mode.

Example:

$ docker run -it --rm \
    -v jenkins_data:/jenkins:ro \
    blacklabelops/alpine bash
$ cd /jenkins
... you operations here....

The volume will be available in read-only mode.

Using Docker Compose

A minimal Docker-Compose file for using volumes can be found in file docker-compose.yml inside the repository directory examples/build.

The file looks like this:

version: '2'

services:
  # Jenkins Master
  jenkins:
    image: blacklabelops/jenkins
    container_name: jenkins
    ports:
     - "8080:8080"
    volumes:
      - jenkinsdata:/jenkins

volumes:
  jenkinsdata:
    external: false

Just start up docker-compose, volumes will be managed on-the-fly:

$ docker-compose up -d