How do I pull a Docker image from one private registry and push it to a second different private registry in Jenkins pipeline

I am able to connect to both private registries from Jenkins and I can pull the image I want to, however I don't know how to push that same image to a different repo.

Note, I am using scripted pipeline syntax since declarative syntax doesn't support pushing/pulling or custom registries as far as I know. I'm also not familiar with Groovy syntax.

Here's what I've got so far for my Jenkinsfile:

node {
    checkout scm

    docker.withRegistry('https://private-registry-1', 'credentials-1') {
        def image = docker.image('my-image:tag')
        image.pull()

        docker.withRegistry('https://private-registry-2', 'credentials-2') {
            image.push()
        }
    }
}

I put the second "withRegistry()" method within the first so that I could use the defined "image" variable.

I successfully connect to the first registry and pull the latest image. From Jenkins console output:

Login Succeeded
[Pipeline] {
[Pipeline] sh
+ docker pull private-registry-1/my-image:tag
tag: Pulling from my-image
Digest: sha256:XXXXX
Status: Image is up to date for private-registry-1/my-image:tag

However, here's the relevant error snippet after connecting to the second registry:

...
Login Succeeded
[Pipeline] {
[Pipeline] sh
+ docker tag my-image:tag private-registry-2/my-image:tag
Error response from daemon: No such image: my-image:tag
...

I am using a Jenkins container on my local Windows machine. It's connected to Docker for Windows through my Ubuntu terminal (Windows Subsystem for Linux).

Solution

The solution was to tag the image before pushing it, final code:

node {
    checkout scm

    stage 'Pull latest image from private-registry-1'

    def image
    docker.withRegistry('https://private-registry-1', 'credentials-1') {
        image = docker.image('my-image:tag')
        image.pull()
    }

    stage 'Push image to private-registry-2'

    // SOLUTION START
    sh 'docker tag private-registry-1/my-image:tag private-registry-2/my-image:tag'
    image = docker.image('private-registry-2/my-image:tag')
    // SOLUTION END

    docker.withRegistry('https://private-registry-2', 'credentials-2') {
        image.push()
    }
}

I don't like how the tagging is done manually through "sh" but I couldn't find a way to do it through the built-in Docker syntax. I will also need to parameterize the image name and tag (my-image:tag) for future use.