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Use Case - Building a RHEL QCOW image using bootc-image-builder

In this example, we will build a container image from a Containerfile and we will generate a QCOW image to spin up a Virtual Machine in KVM.

The Containerfile in the example:

  • Updates packages
  • Installs tmux and mkpasswd to create a simple user password
  • Creates a bootc-user user in the image
  • Adds the wheel group to sudoers
  • Installs Apache Server
  • Enables the systemd unit for httpd
  • Adds a custom index.html
Review Containerfile.qcow 
MAINTAINER Alessandro Rossi <al.rossi87@gmail.com>
FROM registry.redhat.io/rhel9/rhel-bootc:9.5
RUN dnf -y update && dnf -y install tmux mkpasswd
RUN pass=$(mkpasswd --method=SHA-512 --rounds=4096 redhat) && useradd -m -G wheel bootc-user -p $pass
RUN echo "%wheel        ALL=(ALL)       NOPASSWD: ALL" > /etc/sudoers.d/wheel-sudo
RUN dnf -y install httpd && \
    systemctl enable httpd && \
    mv /var/www /usr/share/www && \
    sed -ie 's,/var/www,/usr/share/www,' /etc/httpd/conf/httpd.conf
COPY files/index.html /usr/share/www/html/index.html
EXPOSE 80

Building the image

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

cd use-cases/bootc-image-builder-qcow

To build the image:

podman build -f Containerfile.qcow -t rhel-bootc-vm:qcow .

Testing the image

You can now test it using:

podman run -it --name rhel-bootc-vm --hostname rhel-bootc-vm -p 8080:80 rhel-bootc-vm:qcow

Note: The "-p 8080:80" part forwards the container's http port to the port 8080 on the host to test that it is working.

The container will now start and a login prompt will appear:

On another terminal tab or in your browser, you can verify that the httpd server is working and serving traffic.

Terminal

 ~ ▓▒░ curl localhost:8080
Welcome to the bootc-http instance!

Browser

Generating the QCOW image

To generate the QCOW image we will be using bootc-image-builder container image that will help us transitioning from our newly generated bootable container image to a VM image that can be used with KVM.

The bootc-image-builder container will need rootful access to run, so the first thing we need to do is copying the image from our current user (the one we built the image with) to root:

podman image scp $(whoami)@localhost::rhel-bootc-vm:qcow

Now, verify that the image is correctly present for root user:

 ~ ▓▒░ sudo podman images
REPOSITORY                                TAG         IMAGE ID      CREATED        SIZE
localhost/rhel-bootc-vm                 qcow        0ee1017eb9bc  7 minutes ago  1.81 GB

We are now ready! Let's proceed with the QCOW image creation:

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/rhel9/bootc-image-builder:latest \
    build \
    --type qcow2 \
    --local \
    localhost/rhel-bootc-vm:qcow

We will use the local image we just copied to save in the output folder our generated image.

The process will take care of all required steps (deploying the image, SELinux configuration, filesystem configuration, ostree configuration, etc.), after a couple of minutes we will find in the output:

Generating manifest-qcow2.json ... DONE
Building manifest-qcow2.json
starting -Pipeline source org.osbuild.containers-storage: 8aaabad5f0c2c00eb12666076be4e6843f04e262230e2976dbb1218e96f2ca53
Build
  root: <host>
Pipeline build: 2fb8b2a9ec9dc564950ddc6213d923bdd036c2328a97d0bb785c72fb5b6e1154
Build
  root: <host>
  runner: org.osbuild.rhel82 (org.osbuild.rhel82)
[...]

⏱  Duration: 81s
manifest - finished successfully
build:          2fb8b2a9ec9dc564950ddc6213d923bdd036c2328a97d0bb785c72fb5b6e1154
image:          a578f97344212ef8cdc1a53717b61d72b4cc89504811c7b73e35aafe9a4011e5
qcow2:          ae3acbc9afa8886b03ce112d57177e7a9e0a05819d3f0d7bba9fc0e2663fddf5
vmdk:           a926054ee74e3fa6193efc467be82ad7ff041e58db6712cabf19a82793cbc345
ovf:            02baf8c99f0322217499ddf7ca5f853b74f37926ab7739efc2e7e6dd87ecc8c1
archive:        beb1ba4cddc9a18f49f190d33d9a3ef0221b90d19683f810f170ec4629c55f39
Build complete!

Verify that under the output/qcow2 folder we have our image ready to be used.

 ~/ ▓▒░ tree output
output
├── manifest-qcow2.json
└── qcow2
    └── disk.qcow2

Create the VM in KVM

We will now use the image to spin up our Virtual Machine in KVM.

sudo virt-install \
    --name rhel-bootc-vm \
    --vcpus 4 \
    --memory 4096 \
    --import --disk ./output/qcow2/disk.qcow2,format=qcow2 \
    --os-variant rhel9.5 \
    --network network=default

Wait for the VM to be ready and retrieve the IP address for the domain to log-in using SSH using bootc-user/redhat credentials:

 ~ ▓▒░ VM_IP=$(sudo virsh -q domifaddr rhel-bootc-vm | awk '{ print $4 }' | cut -d"/" -f1) && ssh bootc-user@$VM_IP
Warning: Permanently added '192.168.150.157' (ED25519) to the list of known hosts.
bootc-user@192.168.150.157's password:
[bootc-user@localhost ~]$ curl localhost
Welcome to the bootc-http instance!
[bootc-user@localhost ~]$