Start a Firecracker microVM reproducibly from a JSON config file with --config-file

Documented steps

1. Author a JSON config file mirroring the API resources, e.g. {"boot-source":{"kernel_image_path":"./vmlinux","boot_args":"console=ttyS0"},"drives":[{"drive_id":"rootfs","path_on_host":"./rootfs.ext4","is_root_device":true}],"machine-config":{"vcpu_count":2,"mem_size_mib":1024},"logger":{"log_path":"logs.fifo","level":"Warning"},"metrics":{"metrics_path":"metrics.fifo"}}
2. Launch Firecracker pointing at the config and an API socket: firecracker --config-file /path/to/vm.json --api-sock /tmp/firecracker.socket
3. Any relative paths in the config are resolved relative to the Firecracker process working directory; under the jailer these resources must exist inside the jailed chroot
4. The config can set up boot-source, drives, network-interfaces, machine-config, balloon, vsock, mmds, logger, and metrics in one shot
5. You can combine this with the jailer by passing --config-file after the '--' separator so it is forwarded to the jailed firecracker