Tutorial : Singularity and Docker

2019-09-20 205 words One minute

Contents

How to use private Gitlab Registry with Singularity

With Singularity release 3.3, it is now possible to push and pull a Singularity container into an OCI registry like Docker or Azure Container Registry. It also works with Gitlab registry, which are basically Docker registry. This is a great news for CI/CD with Singularity and Gitlab !

Here is how to proceed with a private Docker GitLab registry:

NB: user is the username gitlab, passwd the associated password, container.sif is the image singularity and project the name of the Gitlab project.

Push: send a container to a registry

singularity push --docker-username user --docker-password passwd container.sif oras://gitlab-registry/user/project:latest

Pull: retrieve a container from a registry

singularity pull --docker-username user --docker-password passwd container.sif oras://gitlab-registry/user/project:latest

It is also possible to use the environment variables SINGULARITY_DOCKER_USERNAME and SINGULARITY_DOCKER_PASSWORD to authenticate, or –docker-login interactive with singularity pull.

Gitlab CI example

Here is a .gitlab-ci.yml example for build and push of a Singularity v3.4.0 container :

image: 
    name: quay.io/singularity/singularity:v3.4.0
    entrypoint: [""]

stages:
  - build
  - deploy

# Build Singularity container
singularity-image:
  stage: build
  script: 
     - singularity build container.sif Singularity
  artifacts:
    paths:
     - container.sif

# Push the image on the registry
deploy:
  stage: deploy
  script:
     - singularity push --docker-username "${CI_REGISTRY_USER}" --docker-password "${CI_REGISTRY_PASSWORD}" app.sif oras://"$CI_REGISTRY_IMAGE"/"$CI_PROJECT_NAME":"$CI_COMMIT_TAG"