Building a Servicing ISO

Introduction

The goal of this document is to produce an installation ISO that utilizes Trident to install an Azure Linux operating system.

Prerequisites

1. Ensure that oras is installed.
2. Ensure Image Customizer container is accessible.
3. Create an Azure Linux image COSI file, assuming the output COSI file is $HOME/staging/osimage.cosi.
4. Create a Trident Host Configuration file, assuming the file is $HOME/staging/host-config.yaml. For this document, the Host Configuration is assumed to reference the COSI file as being contained in the installer ISO at /images/azure-linux.cosi.

Instructions

Step 1: Download the minimal base image

Pull minimal-os as a base image from MCR by running:

mkdir -p $HOME/staging
pushd $HOME/staging
oras pull mcr.microsoft.com/azurelinux/3.0/image/minimal-os:latest --platform linux/amd64
popd

Step 2: Build Trident RPMs

Build the Trident RPMs by running:

make bin/trident-rpms.tar.gz

After running this make command, the RPMs will be built and packaged into bin/trident-rpms.tar.gz and unpacked into bin/RPMS/x86_64:

$ ls bin/RPMS/x86_64/
trident-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm
trident-install-service-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm
trident-provisioning-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm
trident-service-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm
trident-static-pcrlock-files-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm
trident-update-poll-0.3.DATESTRING-dev.COMMITHASH.azl3.x86_64.rpm

Copy RPMs to staging folder:

cp -r bin/RPMS $HOME/staging

Step 3: Create an Image Customizer Configuration

Assuming locations for the Azure Linux image COSI file ($HOME/staging/osimage.cosi) and the Trident Host Configuration file ($HOME/staging/host-config.yaml), follow the Image Customizer documentation to create an Image Customizer configuration file, $HOME/staging/ic-config.yaml:

storage:
  bootType: efi
  disks:
    - partitionTableType: gpt
      maxSize: 4G
      partitions:
        - id: esp
          type: esp
          size: 8M
        - id: rootfs
          size: grow
  filesystems:
    - deviceId: esp
      type: fat32
      mountPoint:
        path: /boot/efi
        options: umask=0077
    - deviceId: rootfs
      type: ext4
      mountPoint:
        path: /
os:
  hostname: installer-iso-mos
  bootloader:
    resetType: hard-reset
  selinux:
    mode: enforcing
  kernelCommandLine:
    extraCommandLine:
      - rd.info
      - console=ttyS0
      - console=tty0
  packages:
    install:
      - netplan
      - trident-install-service
      - trident-provisioning
      - vim
      - curl
      - device-mapper
      - squashfs-tools
      - tar
      - selinux-policy
  services:
    enable:
      - trident-install.service
      - trident-network.service
  additionalFiles:
    - source: host-config.yaml
      destination: /etc/trident/config.yaml
scripts:
  postCustomization:
    - content: |
        # Use more intuitive path for the ISO mount
        ln -s /run/initramfs/live /mnt/trident_cdrom
iso:
  additionalFiles:
    - source: osimage.cosi
      destination: /images/azure-linux.cosi

Step 4: Create Installation ISO

Assuming locations for the base image file ($HOME/staging/image.vhdx) and the Image Customizer configuration file ($HOME/staging/ic-config.yaml), follow the Image Customizer documentation and invoke Image Customizer:

pushd $HOME/staging
docker run --rm \
    --privileged \
    -v ".:/files:z" \
    -v "/dev:/dev" \
    --platform linux/amd64 \
    mcr.microsoft.com/azurelinux/imagecustomizer:0.18.0 \
    --log-level debug \
    --build-dir /build \
    --image-file "/files/image.vhdx" \
    --rpm-source "/files/RPMS/x86_64" \
    --output-image-file "/files/installer.iso" \
    --config-file "/files/ic-config.yaml" \
    --output-image-format iso
popd