Fedora CoreOS - Example script to inject an Ignition configuration file into the virtual machine image. Originates from this blog post: https://www.matthiaspreu.com/posts/fedora-coreos-embed-ignition-config/.

fcos-embed-config-in-image

#!/bin/env bash
set -eo pipefail

#
# Part of a Fedora CoreOS blog post on my website:
# https://www.matthiaspreu.com/posts/fedora-coreos-embed-ignition-config/
#
# Script modifies a FCOS virtual machine image and injects
# an Ignition configuration in it.
#
# Use case: Scenarios where providing the Ingition configuration
# with an external web server is not possible, no cloud
# provider is used, but virtual machine images can still be utilized
# to set up a server (e.g. using a regular server hosting provider).
#
# Initial user "matthias" with password "test" is configured for
# demonstration purposes.
#
# This script actually runs the modfied virtual machine for demonstration
# purposes and therefore the Ignition configuration process is triggered.
# As Iginition is designed to only run once, users creating a modified VM
# image for a real FCOS deployment should obviously exclude this step.
# 

# Generate password hash
function generateHash () {
    local hash="$(echo "test" | mkpasswd --method=SHA-512 --rounds=4096 -s)"
    echo "$hash"
}

# Generate the FCC configuration file
function generateFCC () {
    local hash="$1"
    cat << EOF > fcos.fcc
    variant: fcos
    version: 1.0.0
    passwd:
      users:
      - name: matthias
        password_hash: "$hash"
        groups:
        - wheel
    storage:
      files:
      - path: /etc/hostname
        overwrite: true
        mode: 0644
        contents:
          inline: fcos-server-test
EOF
}

# Download FCOS qcow2 image
ARTEFACT="fedora-coreos-31.20200113.3.1-qemu.x86_64.qcow2.xz"
IMAGENAME="fedora-coreos-31.20200113.3.1-qemu.x86_64.qcow2"
if [ ! -f "$IMAGENAME" ]; then
    curl -o $ARTEFACT https://builds.coreos.fedoraproject.org/prod/streams/stable/builds/31.20200113.3.1/x86_64/$ARTEFACT
    xz -v --decompress $ARTEFACT
fi

# Create a snapshot of the image to not modify original image
rm fcos.qcow2 &>/dev/null || true 
qemu-img create -f qcow2 -b fedora-coreos-31.20200113.3.1-qemu.x86_64.qcow2 fcos.qcow2

# Generate the FCC configuration file
generateFCC "$(generateHash)"

# Generate Ignition file from FCC configuration
podman run -i --rm quay.io/coreos/fcct:v0.2.0 -pretty -strict < fcos.fcc > config.ign

# Inject configuration file into system image
fs_boot_path=$(virt-filesystems -a fcos.qcow2 -l | grep boot | awk -F ' ' '{print $1}')
config_file_path=./config.ign

guestfish add fcos.qcow2 : \
          run : \
          mount "$fs_boot_path" / : \
          mkdir /ignition : \
          copy-in "$config_file_path" /ignition/ : \
          unmount-all : \
          exit

# Launch VM using qemu
qemu-system-x86_64 -machine accel=kvm \
                   -m 2048 -cpu host -nographic \
                   -device virtio-rng-pci \
                   -device virtio-scsi-pci,id=scsi \
                   -drive file=fcos.qcow2,if=none,id=hd0 -device scsi-hd,drive=hd0