Flatcar Linux via Flatcar

flatcar_firecracker.sh

#!/usr/bin/env sh
set -e

command="${1}"
usage="${0} start|stop"

if [ -z "${command}" ]; then
	echo "ERROR: command argument required. [start|stop]"
	echo "${usage}"
	exit 1
fi

bin="${BIN_DIR}"
if [ -z "${bin}" ]; then
	bin="/usr/local/bin"
fi

flatcar_assets="${FLATCAR_ASSETS_DIR}"
if [ -z "${flatcar_assets}" ]; then
	flatcar_assets="/tmp/flatcar"
fi
mkdir -p "${flatcar_assets}"

tap_if="${TAP_IF}"
if [ -z "${tap_if}" ]; then
	tap_if="tap0"
fi

channel="${FLATCAR_CHANNEL}"
if [ -z "${channel}" ]; then
	channel="stable"
fi

if [ ! -f "${bin}/firecracker" ]; then
	curl -L -o "${bin}/firecracker" \
		"https://github.com/firecracker-microvm/firecracker/releases/download/v0.21.0/firecracker-v0.21.0-x86_64"
	chmod +x "${bin}/firecracker"
fi

if [ ! -f "${bin}/extract-vmlinux" ]; then
	curl -L -o "${bin}/extract-vmlinux" "https://raw.githubusercontent.com/torvalds/linux/master/scripts/extract-vmlinux"
	chmod +x "${bin}/extract-vmlinux"
fi

if [ ! -f "${flatcar_assets}/vmlinux" ]; then
	curl -L -o "${flatcar_assets}/vmlinuz" "https://${channel}.release.flatcar-linux.net/amd64-usr/current/flatcar_production_pxe.vmlinuz"
	/usr/local/bin/extract-vmlinux "${flatcar_assets}/vmlinuz" > "${flatcar_assets}/vmlinux"
fi

if [ ! -f "${flatcar_assets}/initramfs" ]; then
	curl -L "https://${channel}.release.flatcar-linux.net/amd64-usr/current/flatcar_production_pxe_image.cpio.gz" |\
		gunzip > "${flatcar_assets}/initramfs"
fi

echo "[INFO] Determining public facing network interface."
default_route="$(ip route|grep default|awk '{print $3}')"
host_if="$(cat /proc/net/arp|grep -F "${default_route}"|awk '{print $6}'|head -n1)"

if [ -z "${host_if}" ]; then
	echo "ERROR: Unable to determine public facing network interface."
	exit 1
fi
echo "[INFO] Using \"${host_if}\"."

if [ "${command}" == "start" ]; then
	vm_config="${VM_CONFIG}"
	if [ -z "${vm_config}" ]; then
		echo "[ERROR] VM_CONFIG firecracker json config file not provided."
		exit 1
	fi
	echo "[INFO] Using firecracker VM config \"${vm_config}\"."

	vm_mac="$(cat "${vm_config}" | jq '.["network-interfaces"]|.[]|.guest_mac' -r)"
	echo "[INFO] VM Mac: \"${vm_mac}\"."

	echo "[INFO] Creating macvtap network interface \"${tap_if}\" from interface \"${host_if}\"."
	ip link add link "${host_if}" name "${tap_if}" type macvtap mode bridge
	ip link set tap0 address "${vm_mac}" up

	"${bin}/firecracker" --no-api --config-file "${vm_config}"
elif [ "${command}" == "stop" ]; then
	set +e
	echo "[INFO] Deleting macvtap network interface \"${tap_if}\""
	ip link del dev "${tap_if}"
	exit 0
fi