Force a Jenkins pipeline job to pull a new private image from Dockerhub

Question

I want to pull a new version of a specific private image with a specific tag on Docker Hub using the Jenkins Docker pipeline plugin. The Docker shell commands would look like:

docker login -u user -p password
docker pull user/foo:bar

Something like this seems like it ought to work:

node () {
    image = docker.image('user/foo:bar')
    image.pull()
    image.inside {
        // Commands to run in the container

But there's no way to execute the login step, so I always get the error:

Error response from daemon: pull access denied for user/foo, repository does not exist or may require 'docker login'.

I've gone through the documentation and the code, but the documentation doesn't even mention pulling and the examples in the code don't show how to log in to pull a private image. I can manually script it but the whole point of using the Docker pipeline plugin is to avoid directly scripting Docker commands.

Answer 1

I believe what you will need here is the withRegistry function. It can be used as follows

docker.withRegistry('<registry-url>', '<credential-id>') {
    image = docker.image('user/foo:bar')
    image.pull()
}

Everything within the withRegistry block will use that registry and authentication for pulling the image.

Where the <registry-url> in this case is the URL for the Dockerhub registry. I believe the Dockerhub registry URL is https://registry.hub.docker.com

The <credential-id> is the ID of the Dockerhub credentials stored in Jenkins.

To add these credentials navigate from the Jenkins index page to Credentials -> System -> Global credentials -> Add Credentials.

Once on this page you will need to select Kind as Username with password. The scope should be Global. The username and password fields are your username and password for Dockerhub.

The ID field is whatever text you want to be the <credential-id>. For example if you make the ID field docker-hub-credentials that will need to be the second argument to withRegistry.

Here is an example of what the page to add credentials could look like.