Fedora CoreOS - Example script to setup a FCOS virtual machine using QEMU. Originates from this blog post: https://www.matthiaspreu.com/posts/fedora-coreos-first-steps/.

fcos-qemu-demo

#!/bin/env bash
set -eo pipefail

#
# Part of an introductory Fedora CoreOS blog post on my website:
# https://www.matthiaspreu.com/posts/fedora-coreos-first-steps/
#
# Script sets up a FCOS virtual machine using QEMU. 
#
# Initial user "matthias" with password "test" can be used.
# One SSH keypair for the users "core" and "matthias" without a 
# passphrase is created as well.
# 
# Script sets up additional storage in the virtual machine to demonstrate
# some possibilities with Ignition.
#

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

# Generate ssh key
function generateSSHKey () {
    rm ./id_rsa_fcos_example ./id_rsa_fcos_example.pub &>/dev/null || true
    local pubKey="$(ssh-keygen -t rsa -b 4096 -q -N "" -f ./id_rsa_fcos_example && ssh-keygen -y -f ./id_rsa_fcos_example)"
    echo "$pubKey"
}

# Generate the FCC configuration file
function generateFCC () {
    local pubKey="$1"
    local hash="$2"
    cat << EOF > fcos.fcc
    variant: fcos
    version: 1.0.0
    passwd:
      users:
      - name: core
        ssh_authorized_keys:
        - "$pubKey"
      - name: matthias
        ssh_authorized_keys:
        - "$pubKey"
        password_hash: "$hash"
        groups:
        - wheel
    storage:
      disks:
      - device: /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_hd1
        wipe_table: true
        partitions:
        - label: "disk.test"
          number: 0
          wipe_partition_entry: true
      filesystems:
      - path: /var/storage
        device: /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_hd1
        wipe_filesystem: true
        format: ext4
        label: STORAGE
      files:
      - path: /etc/hostname
        overwrite: true
        mode: 0644
        contents:
          inline: fcos-server-test
    systemd:
      units:
      - name: var-storage.mount
        enabled: true
        contents: |
          [Mount]
          What=/dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_hd1
          Where=/var/storage
          Type=ext4

          [Install]
          WantedBy=local-fs.target
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

# Create additional hard disk to demonstrate handling of storage
rm storage.qcow2 &>/dev/null || true
qemu-img create -f qcow2 storage.qcow2 500M

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

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

# 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 \
                   -drive file=storage.qcow2,if=none,id=hd1 -device scsi-hd,drive=hd1 \
                   -fw_cfg name=opt/com.coreos/config,file=./fcos.ign