Install Fedora CoreOS by running `coreos-installer` directly on block device `/dev/loop0`

fcos-installer

#!/usr/bin/env bash

function create_ign_file() {
    cat >> base3.ign <<EOF
{
    "ignition": {
        "version": "3.0.0"
    },
    "passwd": {
        "users": [
            {
                "name": "core",
                "sshAuthorizedKeys": [
                    "ssh-rsa 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 abai@unused-10-15-17-19.yyz.redhat.com"
                ]
            }
        ]
    },
    "systemd": {
        "units": [
          {
            "dropins": [
              {
                "contents": "[Service]\nTTYVTDisallocate=no\nExecStart=\nExecStart=-/usr/sbin/agetty --autologin core --noclear %I xterm-256color",
                "name": "autologin.conf"
              }
            ],
            "name": "serial-getty@ttyS0.service"
          }
        ]
      }
}
EOF
}

if [[ $1 ==  "install" ]];
then
    set -x

    # if the coreos-installer directory does not exist
    # pull the coreos-install repo from github
    [[ -d coreos-installer ]] || \
        git clone https://github.com/coreos/coreos-installer.git \
        ; cd coreos-installer

    # build the binary file
    cargo build

    # create a QEMU image
    qemu-img create -f qcow2 fcos.qcow2 8G

    # shrink/extend the size of the image file
    truncate -s 8G fcos.qcow2

    # set up a loop device
    sudo losetup -P /dev/loop0 fcos.qcow2

    # run the coreos-installer binary
    create_ign_file && \
        sudo target/debug/coreos-installer install /dev/loop0 -s testing --ignition-file base3.ign

    # run the virtual machine with QEMU
    qemu-system-x86_64 -accel kvm -name fcos -m 2048 -cpu host -smp 2 -netdev user,id=eth0,hostname=coreos -device virtio-net-pci,netdev=eth0 -drive file=fcos.qcow2

    set +x
    exit 0
fi

if [[ $1 == "clean" ]];
then
    set -x

    [[ $(basename $PWD) != "coreos-installer" ]] && cd coreos-installer
    # detach the file or device associated with the specified loop device(s)
    sudo losetup -d /dev/loop0
    # remvoes qcow2 and ignition config file
    rm -f fcos.qcow2
    rm -f base3.ign

    set +x
    exit 0
fi

printf "Available options:\n\tinstall\n\tclean\n"
exit 1

Please replace the sshAuthorizedKeys section with your own ssh pubkey.