diff --git a/script/build-vm.sh b/script/build-vm.sh
index 455c867..a4d8afd 100755
--- a/script/build-vm.sh
+++ b/script/build-vm.sh
@@ -13,47 +13,89 @@ echo "        image:    ${qcow2}"
 
 sleep 5
 
-echo "[+] updating NixOS config"
-cd /etc/nixos
-doas git pull --rebase local master
+build_nixos_vm () {
 
-if [[ -d "${build_dir}" ]]
-then
-    echo "[+] removing ${build_dir}"
-    sleep 2
-    rm -r "${build_dir}"
-fi
+    echo "[+] updating NixOS config"
+    cd /etc/nixos
+    doas git pull --rebase local master
 
-mkdir "${build_dir}"
-cd "${build_dir}"
-nixos-rebuild build-vm
+    if [[ -d "${build_dir}" ]]
+    then
+	echo "[+] removing ${build_dir}"
+	sleep 2
+	rm -r "${build_dir}"
+    fi
 
-echo "[+] Spinning up VM; kill it when you see the line"
-echo "	'Virtualisation disk image created.'"
-"${build_dir}/result/bin/run-$(hostname -s)-vm"
-doas qemu-img resize "${qcow2}" 256G
+    mkdir "${build_dir}"
+    cd "${build_dir}"
+    nixos-rebuild build-vm
 
-doas modprobe nbd max_part=8
+    echo "[+] Spinning up VM; kill it when you see the line"
+    echo "	'Virtualisation disk image created.'"
+    "${build_dir}/result/bin/run-$(hostname -s)-vm"
+    doas qemu-img resize "${qcow2}" 256G
 
-echo "[+] connecting to network block driver"
-echo "    note: on failure, you may need to manually run"
-echo "    doas qemu-nbd --disconnect /dev/nbd0"
-doas qemu-nbd --connect=/dev/nbd0 ${qcow2}
+    doas modprobe nbd max_part=8
 
-if [[ -d "${mount_point}" ]]
-then
-    echo "[+] removing ${mount_point}"
-    sleep 2
-    rm -r "${mount_point}"
-fi
+    echo "[+] connecting to network block driver"
+    echo "    note: on failure, you may need to manually run"
+    echo "    doas qemu-nbd --disconnect /dev/nbd0"
+    doas qemu-nbd --connect=/dev/nbd0 ${qcow2}
 
-mkdir -p "${mount_point}"
-doas mount /dev/nbd0 "${mount_point}"
+    if [[ -d "${mount_point}" ]]
+    then
+	echo "[+] removing ${mount_point}"
+	sleep 2
+	rm -r "${mount_point}"
+    fi
 
-rsync --progress -auvz "${HOME}/" "${mount_point}/home/kyle/"
+    mkdir -p "${mount_point}"
+    doas mount /dev/nbd0 "${mount_point}"
 
-echo "[+] finished, cleaning up"
-doas unmount "${mount_point}"
-doas qemu-nbd --disconnect /dev/nbd0
-doas rmdir "${mount_point}"
-doas rm -r "${build_dir}"
+    rsync --progress -auvz "${HOME}/" "${mount_point}/home/kyle/"
+
+    echo "[+] finished, cleaning up"
+    doas umount "${mount_point}"
+    doas qemu-nbd --disconnect /dev/nbd0
+    doas rmdir "${mount_point}"
+    doas rm -r "${build_dir}"
+}
+
+cleanup () {
+    if [[ -d "${build_dir}" ]]
+    then
+	echo "[+] removing ${build_dir}"
+	sleep 2
+	rm -r "${build_dir}"
+    fi
+
+    if [[ ! -z "$(mount | grep /dev/nbd0)" ]]
+    then
+	echo "[+] unmounting network block device"
+	doas umount /dev/nbd0
+    fi
+
+    echo "[+] disconnecting network block device"
+    echo "    it's okay if this fails"
+    doas qemu-nbd --disconnect /dev/nbd0
+
+    if [[ -d "${mount_point}" ]]
+    then
+	echo "[+] removing ${mount_point}"
+	sleep 2
+	rm -r "${mount_point}"
+    fi
+}
+
+case "${1:-build}" in
+    build)
+	build_nixos_vm
+	;;
+    cleanup)
+	cleanup
+	;;
+    *)
+	echo "[!] Valid commands are build, cleanup"
+	exit 1
+	;;
+esac