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Use Case - Embedding a Containerized application into Image Mode

In this example, we want to show how to easily embed a containerized application into Image Mode, and let bootc handle its lifecycle.

To achieve this, we will link the application image as a Logically Bound Image (LBI), that allows to link one or more specific container images to a bootc image.

We will have two Containerfiles, one for the application and one for the bootc image.

The application Containerfile will only add a custom index.html page to the Nginx base image:

Review Containerfile.nginx 
FROM registry.access.redhat.com/ubi10/ubi-minimal

RUN microdnf install -y nginx
COPY index.html /usr/share/nginx/html

CMD ["nginx", "-g", "daemon off;"]

The bootc containerfile in this example will:

  • Create the systemd unit for the container
  • Link the container to bootc
Review Containerfile 
FROM registry.redhat.io/rhel10/rhel-bootc:latest

RUN dnf -y install tmux mkpasswd container-tools \
    && dnf -y clean all

RUN pass=$(mkpasswd --method=SHA-512 --rounds=4096 redhat) && useradd -m -G wheel bootc-user -p $pass \
    && echo "%wheel        ALL=(ALL)       NOPASSWD: ALL" > /etc/sudoers.d/wheel-sudo

COPY ./nginx.container /usr/share/containers/systemd/nginx.container
RUN ln -s /usr/share/containers/systemd/nginx.container /usr/lib/bootc/bound-images.d/nginx.container

Review the container unit

Together with the Containerfile, we can see a special file, nginx.container, that will take care of defining the Quadlet for our container.

The definition includes the ports to expose, the image to run and the restart policy.

Review Containerfile.upgrade 
[Container]
Image=quay.io/QUAY_USER/nginx-lbi:v1.0
GlobalArgs=--storage-opt=additionalimagestore=/usr/lib/bootc/storage
PublishPort=8080:80
[Unit]
Description=Custom NGINX server
[Install]
WantedBy=default.target
[Service]
Restart=always

Login to the container registry and fix the username

We can start by fixing the QUAY_USER variable with your quay.io username:

export QUAY_USER=YOURQUAYUSERNAME

Log-in to Quay.io:

podman login -u $QUAY_USER quay.io

Building and pushing the application image

From the root folder of the repository, switch to the use case directory:

cd use-cases/image-mode-podman-container

You can build the image right from the Containerfile using Podman:

podman build -f Containerfile.nginx -t quay.io/$QUAY_USER/nginx-lbi:v1.0 .

Push the image:

podman push quay.io/$QUAY_USER/nginx-lbi:v1.0

Building the bootc image

From the root folder of the repository, switch to the use case directory:

cd use-cases/image-mode-podman-container

Before proceeding with the build, replace the QUAY_USER variable in the nginx.container file:

sed -i "s/QUAY_USER/$QUAY_USER/g' nginx.container

You can build the image right from the Containerfile using Podman:

podman build -f Containerfile -t quay.io/$QUAY_USER/rhel-image-mode:containerized-nginx .

And let's push this image too:

podman quay.io/$QUAY_USER/rhel-image-mode:containerized-nginx

Convert to QCOW2 and create a Virtual Machine in KVM

Let's proceed with the QCOW image creation. During the conversion, the image will be made available to the target system, so that at boot it will be available and ready to be executed:

sudo podman run \
    --rm \
    -it \
    --privileged \
    --pull=newer \
    --security-opt label=type:unconfined_t \
    -v $(pwd)/output:/output \
    -v /var/lib/containers/storage:/var/lib/containers/storage \
    registry.redhat.io/rhel10/bootc-image-builder:latest \
    build \
    --type qcow2 \
    quay.io/$QUAY_USER/rhel-image-mode:containerized-nginx

We can then proceed with the creation of the VM

sudo virt-install \
    --name rhel-bootc-vm \
    --vcpus 4 \
    --memory 4096 \
    --import --disk ./output/qcow2/disk.qcow2,format=qcow2 \
    --os-variant rhel10.0 \
    --network network=default

Retrieve the address and test the application

Now that the VM is in place, we only need the IP address to test it out. As we exposed the application container port 80 to the host port 8080, we will be able to just jump in a browser and verify that the page is correctly showing!

To retrieve the IP:

virsh domifaddr rhel-bootc-vm | awk '/ipv4/ {print $4}' | cut -d/ -f1 | head -n1

In a browser, go to http://{VM_IP}:8080 to verify that everything is working as expected!

Updating the application container image

To update the application container image, it will be enough to:

  • Create a new version of our application image - i.e. quay.io/$QUAY_USER/nginx-lbi:v2.0
  • Reference the new version in the nginx.container file
  • Rebuild the Image Mode container image
  • Run the bootc upgrade command on the target host