4 Creating Custom Images #

Base images of SLES are provided on the SUSE registry in the suse/ namespace. To obtain the base SLES images from SUSE registry and make them available to the local Docker instance, use the following command:

> docker pull registry.suse.com/suse/IMAGENAME

Pre-built images do not have repositories configured. But when the Docker host has a SLE subscription that provides access to the product used in the image, Zypper will automatically have access to the right repositories.

You can customize the Docker image as described in Section 4.2, “Customizing SLES Docker Images”.

> docker pull registry.suse.com/suse/sle15:15.1

The pre-built images do not have any repository configured and do not include any modules or extensions. They contain a zypper service that contacts either the SUSE® Customer Center (SUSE Customer Center) or your Repository Mirroring Tool (RMT) server, according to the configuration of the SLE host that runs the Docker container. The service obtains the list of repositories available for the product used by the Docker image. You can also directly declare extensions in your Dockerfile (for details refer to Section 4.2.4, “Adding SLE Extensions and Modules to Images”.

You do not need to add any credentials to the Docker image because the machine credentials are automatically injected into the container by the docker daemon. They are injected inside of the /run/secrets directory. The same applies to the /etc/SUSEConnect file of the host system, which is automatically injected into the /run/secrets directory.

Note: Credentials and Security

The contents of the /run/secrets directory are never committed to a Docker image, hence there is no risk of your credentials leaking.

Note: Building Images on Systems Registered with RMT

When the host system used for building Docker images is registered with RMT, the default behavior allows only building containers of the same code base as the host. For example, if your Docker host is an SLE 15 system, you can only build SLE 15-based images on that host by default. To build images for a different SLE version, for example SLE 12 on an SLE 15 host, the host machine credentials for the target release can be injected into the container as outlined below.

When the host system is registered with SUSE Customer Center, this restriction does not apply.

Note: Building Container Images in On-Demand SLE Instances in the Public Cloud

When building container images on SLE instances that were launched as so-called "on-demand" or "pay as you go" instances on a Public Cloud (AWS, GCE, or Azure), some additional steps have to be performed. For installing packages and updates, the "on-demand" public cloud instances are connected to a public cloud-specific update infrastructure, which is based around RMT servers operated by SUSE on the various Public Cloud Providers. Some additional steps are required to locate the required services and authenticate with them.

A new service was introduced to enable this, called containerbuild-regionsrv. This service is available in the public cloud images provided through the Marketplaces of the various Public Cloud Providers. So before building an image, this service has to be started on the public cloud instance by running the following command:

> sudo systemctl start containerbuild-regionsrv

To start it automatically after system startup, enable it with systemctl:

> sudo systemctl enable containerbuild-regionsrv

The Zypper plugins provided by the SLE base images will then connect to this service for retrieving authentication details and information about which update server to talk to. In order for that to work the container has to be built with host networking enabled, like the following example:

> docker build --network host build-directory/

Since update infrastructure in the Public Clouds is based upon RMT, the same restrictions with regard to building SLE images for SLE versions differing from the SLE version of the host apply here as well (see Note: Building Images on Systems Registered with RMT).

To obtain the list of repositories, use the following command:

> sudo zypper ref -s

It will automatically add all the repositories to your container. For each repository added to the system a new file will be created under /etc/zypp/repos.d. The URLs of these repositories include an access token that automatically expires after 12 hours. To renew the token call the zypper ref -s command. It is secure to commit these files to a Docker image.

If you want to use a different set of credentials, place a custom /etc/zypp/credentials.d/SCCcredentials file inside of the Docker image. It contains the machine credentials that have the subscription you want to use. The same applies to the SUSEConnect file: to override the file available on the host system that is running the Docker container, add a custom /etc/SUSEConnect file inside of the Docker image.

Now you can create a custom Docker image by using a Dockerfile as described in Section 4.2.1 and Section 4.2.2. In case you would like to move your application to a Docker container, refer to Chapter 5, Creating Docker Images of Applications. After you have edited the Dockerfile, build the image by running the following command in the same directory in which the Dockerfile resides:

> docker build .

FROM registry.suse.com/suse/sles12sp4

RUN zypper ref -s
RUN zypper -n in vim

FROM registry.suse.com/suse/sles12sp4

# Import the crt file of our private SMT server
ADD http://smt.test.lan/smt.crt /etc/pki/trust/anchors/smt.crt
RUN update-ca-certificates

RUN zypper ref -s
RUN zypper -n in vim

FROM registry.suse.com/suse/sle15

RUN zypper ref -s
RUN zypper -n in vim

FROM registry.suse.com/suse/sle15

# Import the crt file of our private SMT server
ADD http://smt.test.lan/smt.crt /etc/pki/trust/anchors/smt.crt
RUN update-ca-certificates

RUN zypper ref -s
RUN zypper -n in vim

> docker inspect registry.suse.com/suse/sle15
[...]
            "Labels": {
                "com.suse.sle.base.created": "2019-06-20T18:21:37.729383880Z",
                "com.suse.sle.base.description": "Image containing a minimal environment for containers based on SUSE Linux Enterprise Server 15 SP1.",
                "com.suse.sle.base.disturl": "obs://build.suse.de/SUSE:SLE-15-SP1:Update:CR/images/20efed47827dc48da9537c1aeed4dbe2-sles15-image",
                "com.suse.sle.base.reference": "registry.suse.com/suse/sle15:15.1.6.2.31",
                "com.suse.sle.base.title": "SUSE Linux Enterprise Server 15 SP1 Base Container",
                "com.suse.sle.base.url": "https://www.suse.com/products/server/",
                "com.suse.sle.base.vendor": "SUSE LLC",
                "com.suse.sle.base.version": "15.1.6.2.31",
                "org.openbuildservice.disturl": "obs://build.suse.de/SUSE:SLE-15-SP1:Update:CR/images/20efed47827dc48da9537c1aeed4dbe2-sles15-image",
                "org.opencontainers.image.created": "2019-06-20T18:21:37.729383880Z",
                "org.opencontainers.image.description": "Image containing a minimal environment for containers based on SUSE Linux Enterprise Server 15 SP1.",
                "org.opencontainers.image.title": "SUSE Linux Enterprise Server 15 SP1 Base Container",
                "org.opencontainers.image.url": "https://www.suse.com/products/server/",
                "org.opencontainers.image.vendor": "SUSE LLC",
                "org.opencontainers.image.version": "15.1.6.2.31",
                "org.opensuse.reference": "registry.suse.com/suse/sle15:15.1.6.2.31"
            }
[...]