deploy-qemu

#!/usr/bin/env python3

import os
import shutil
import subprocess
import sys
import tempfile


HELP_TEXT="""deploy-qemu IMAGE USERDATA

Starts an ephemeral virtual machine in qemu, injecting configuration via
cloud-init. Stopping this script stops the VM and discards all data.

IMAGE    -- An os image that can be booted by qemu and has cloud-init
            installed and enabled. No changes are made to this file.

USERDATA -- A cloud-init user-data config file, or a directory of
            configuration as accepted by the `gen-user-data` tool.

In addition, if the QEMU_EXTRA_ARGS environment variable is defined, it adds
its content as additional arguments to qemu."""


if len(sys.argv) != 3:
    print(HELP_TEXT)
    sys.exit(1)

script_dir = os.path.dirname(os.path.realpath(__file__))
image = sys.argv[1]
userdata = sys.argv[2]

qemu_extra_args = os.getenv("QEMU_EXTRA_ARGS")
qemu_extra_args = qemu_extra_args.split(' ') if qemu_extra_args is not None else []

with tempfile.TemporaryDirectory(prefix="qemu-tmp-") as workdir:
    os.mkdir(os.path.join(workdir, "cidata"))

    if os.path.isdir(userdata):
        gen_user_data = subprocess.run([os.path.join(script_dir, "gen-user-data"), userdata], check=True, capture_output=True, encoding="utf-8")
        with open(os.path.join(workdir, "cidata", "user-data"), "w") as f:
            f.write(gen_user_data.stdout)
    else:
        shutil.copyfile(userdata, os.path.join(workdir, "cidata", "user-data"))

    with open(os.path.join(workdir, "cidata", "meta-data"), "w") as f:
        f.writelines(["instance-id: nocloud\n", "local-hostname: vm\n"])

    if sys.platform == "linux":
        subprocess.run(["mkisofs", 
                        "-input-charset", "utf-8", 
                        "-output", f"{workdir}/cloudinit.iso",
                        "-volid", "cidata",
                        "-joliet",
                        "-rock", 
                        "-quiet",
                        "-graft-points",
                        f"{workdir}/cidata/user-data",
                        f"{workdir}/cidata/meta-data"], check=True)
    elif sys.platform == "darwin":
        # conviently uses the last component of source as volumeid, which has to be cidata
        subprocess.run(["hdiutil", "makehybrid", "-iso", "-joliet", "-o", f"{workdir}/cloudinit.iso", f"{workdir}/cidata"], check=True)

    subprocess.run(["qemu-system-x86_64",
        "-M", "accel=kvm:hvf",
        "-m", "1024",
        "-snapshot",
        "-cpu", "host",
        "-net", "nic,model=virtio",
        "-net", "user,hostfwd=tcp::2222-:22,hostfwd=tcp::4430-:443",
        "-cdrom", f"{workdir}/cloudinit.iso",
        *qemu_extra_args,
        image])