give the ext4 image a disk label

 - this allows the kernel cmdline and fstab to refer to it by label
   instead of by /dev/sda or /dev/vda (depending on whether the disk is
   attached to qemu via virtio or not)
 - it allows other consumers of the image to detect that this is an
   image created by debvm and then treat it accordingly

1 files changed, 9 insertions, 1 deletions

diff --git a/debvm-run b/debvm-run
index 4ec9122..9b26a76 100755
--- a/debvm-run
+++ b/debvm-run
@@ -46,6 +46,14 @@ done
 test -f "$IMAGE" || die "image '$IMAGE' not found"
 test -s "$IMAGE" || die "image '$IMAGE' is empty"
 
+if ! printf '\123\357' | cmp --bytes=2 "$IMAGE" - 1080; then
+	die "image '$IMAGE' is not in ext4 format"
+fi
+
+if ! printf 'debvm\000' | cmp --bytes=6 "$IMAGE" - 1144; then
+	die "image '$IMAGE' was not created by debvm-create (wrong disk label)"
+fi
+
 cleanup() {
 	set +x
 	test -n "$KERNELTMP" && rm -f "$KERNELTMP"
@@ -78,7 +86,7 @@ INITRDNAME=$(/sbin/debugfs "$IMAGE" -R "stat initrd.img" | sed 's/Fast link dest
 test -n "$KERNELNAME" || die "failed to discover kernel image"
 test -n "$INITRDNAME" || die "failed to discover initrd image"
 
-KERNEL_CMDLINE="root=/dev/vda rw"
+KERNEL_CMDLINE="root=LABEL=debvm rw"
 NETDEV="user,id=net0"
 
 set -- \