Public images on the registries can be pulled without any setup, but private registries that are gated behind logins will require login on Apptainer. The apptainer registry login command authenticates your user for any OCI-compatible container registry, such as Docker Hub or GitHub Container Registry. Your login information is then saved for future pulls from that registry.

The typical form supplies a username and the registry address, then prompts you for a password or token:

Alternatively, you may supply both the username and password through environment variables. Set APPTAINER_DOCKER_USERNAME and APPTAINER_DOCKER_PASSWORD before the pull, and Apptainer authenticates without prompting when pulling private registries:

Apptainer also provides commands to manage the registries you are logged in to. Use apptainer registry list to see your active logins, and apptainer registry logout to remove a registry's stored credentials.