debvm-create: Output image in tar format if step "ext4" is skipped

Outputting the image in tar format breaks interoperability with
`debvm-run`, but makes it easier to inspect, convert or perform
additional modifications of the generated image.

1 files changed, 13 insertions, 2 deletions

diff --git a/bin/debvm-create b/bin/debvm-create
index 8c86eca..4651e00 100755
--- a/bin/debvm-create
+++ b/bin/debvm-create
@@ -15,7 +15,7 @@ B<debvm-create> [B<-a> I<architecture>] [B<-h> I<hostname>] [B<-k> F<sshkey>] [B
 
 =head1 DESCRIPTION
 
-B<debvm-create> is essentially a thin wrapper around B<mmdebstrap> for creating a raw ext4 filesystem image for booting with B<debvm-run>.
+B<debvm-create> is essentially a thin wrapper around B<mmdebstrap> for creating a raw ext4 or tar filesystem image for booting with B<debvm-run>.
 The purpose of these images primarily is testing the different releases and architectures without access to a physical machine of that architecture.
 Beyond essential packages, the image will contain B<apt>, an init system and a suitable kernel package.
 Notably absent is a bootloader and a partition table.
@@ -229,11 +229,17 @@ if ! check_skip kernel; then
 	set -- "--customize-hook=$SHARE_DIR/customize-kernel.sh" "$@"
 fi
 
+MMFORMAT=ext2
+# output a tarball if the ext4 step is skipped
+if check_skip ext4; then
+	MMFORMAT=tar
+fi
+
 # construct mmdebstrap options as $@:
 set -- \
 	--verbose \
 	--variant=apt \
-	--format=ext2 \
+	"--format=$MMFORMAT" \
 	--include=init \
 	"--architecture=$ARCHITECTURE" \
 	'--customize-hook=echo "LABEL=debvm / ext4 defaults 0 1" >"$1/etc/fstab"' \
@@ -293,6 +299,11 @@ set -ex
 
 mmdebstrap "$@"
 
+{ set +x; } 2>/dev/null
+check_skip ext4 && exit
+
+set -x
+
 truncate -s ">$SIZE" "$IMAGE"
 /sbin/tune2fs -L debvm -c 0 -i 0 -O dir_index,dir_nlink,extents,extra_isize,flex_bg,has_journal,huge_file "$IMAGE"
 /sbin/resize2fs -b "$IMAGE"