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

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

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.iso 
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 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
RUN echo "Welcome to the bootc-http instance!" > /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-iso

To build the image:

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

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:iso

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

Tagging and pushing the image

To tag and push the image you can simply run (replace YOURQUAYUSERNAME with the account name):

export QUAY_USER=YOURQUAYUSERNAME

podman tag rhel-bootc-vm:httpd quay.io/$QUAY_USER/rhel-bootc-vm:iso

Log-in to Quay.io:

podman login -u $QUAY_USER quay.io

And push the image:

podman push quay.io/$QUAY_USER/rhel-bootc-vm:iso

Customize the image

In this example, we will not create the user in the image, but we will provide a customization using the config.toml file. It can be used to perform customizations of users, groups, etc.

A sample config.toml is already present in the use case directory, that we will use to create our bootc-user/redhat and add it to the wheel group is as follows:

  [[blueprint.customizations.user]]
  name = "bootc-user"
  password = "redhat"
  groups = ["wheel"]

Generating the ISO image

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

The bootc-image-builder container will need rootful access to run, let's proceed with the ISO image creation:

sudo podman run \
    --rm \
    -it \
    --privileged \
    --pull=newer \
    --security-opt label=type:unconfined_t \
    -v $(pwd)/output:/output \
    -v /var/lib/containers/storage:/var/lib/containers/storage \
    registry.redhat.io/rhel9/bootc-image-builder:latest \
    build \
    --type iso \
    quay.io/$QUAY_USER/rhel-bootc-vm:iso

We will use the image we pushed before to create our image in the output folder.

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 manifest-iso.json
DONE
Building manifest-iso.json
starting -Pipeline source org.osbuild.containers-storage: f1027594ecbee0b434f86af01d4ba21b478265c0c773e35c387858d0fc4bf16d
Build
  root: <host>
Pipeline source org.osbuild.curl: 07337b98b3c859adfb37b011d83cf0511884147bf999e7869ffbf9074b529a4f
Build
  root: <host>
[...]

⏱  Duration: 9s
org.osbuild.implantisomd5: 3798a4bfccd982e2e24d6130c4174eba98ad12f94a41b25ec8884a8cfccaf8ce {
  "filename": "install.iso"
}
['implantisomd5', '/run/osbuild/tree/install.iso']
Inserting md5sum into iso image...
md5 = 66adac8cb9127c31942085bade81a8d4
Inserting fragment md5sums into iso image...
fragmd5 = 9d5d936a1b5c8f9bf96e1e14c164898d8e2fcf45652dbee6f3741e17b5ca
frags = 20
Setting supported flag to 0

⏱  Duration: 6s
manifest - finished successfully
build:          9133fb8610ab053dae7e281e6a6655dbb912c4530d32e4da75c06b8713a87c80
anaconda-tree:  fcd61d1236a42900977530f12f45fe452f2f0c8bf3c80a7ba60cb45ffe4bf36d
rootfs-image:   0a517e05ab42f947beec8dae4d2da338ca9cc7fe17b1daba013e24b1c60aeadf
efiboot-tree:   61a20c820b40436ce7bd6d1a74c6b97a05f7c8800b678083942e814cf9f7cc0e
bootiso-tree:   fd0185a1c0eb53df152acd85195c016315e79dd5dc32eb32d07abf0e21251c62
bootiso:        3798a4bfccd982e2e24d6130c4174eba98ad12f94a41b25ec8884a8cfccaf8ce
Build complete!
Results saved in

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

 ~/ ▓▒░ tree output
output/
├── bootiso
│   └── install.iso
└── manifest-iso.json

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 \
    --cdrom ./output/bootiso/install.iso \
    --os-variant rhel9.5 \
    --disk size=20 \
    --network network=default

We can check that the installer is running using the VM Console:

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 '192.168.124.209' (ED25519) to the list of known hosts.
bootc-user@192.168.124.209's password:
This is a RHEL 9.5 VM installed using a bootable container as an rpm-ostree source!
[bootc-user@localhost ~]$