@@ -4,7 +4,7 @@ set -e

 mkimg="$(basename "$0")"

 usage() {

-	echo >&2 "usage: $mkimg [-d dir] [-t tag] script [script-args]"

+	echo >&2 "usage: $mkimg [-d dir] [-t tag] [-c compression] script [script-args]"

 	echo >&2 "   ie: $mkimg -t someuser/debian debootstrap --variant=minbase jessie"

 	echo >&2 "       $mkimg -t someuser/ubuntu debootstrap --include=ubuntu-minimal --components=main,universe trusty"

 	echo >&2 "       $mkimg -t someuser/busybox busybox-static"

@@ -16,16 +16,19 @@ usage() {

 scriptDir="$(dirname "$(readlink -f "$BASH_SOURCE")")/mkimage"

-optTemp=$(getopt --options '+d:t:h' --longoptions 'dir:,tag:,help' --name "$mkimg" -- "$@")

+optTemp=$(getopt --options '+d:t:c:hC' --longoptions 'dir:,tag:,compression:,no-compression,help' --name "$mkimg" -- "$@")

 eval set -- "$optTemp"

 unset optTemp

 dir=

 tag=

+compression="auto"

 while true; do

 	case "$1" in

 		-d|--dir) dir="$2" ; shift 2 ;;

 		-t|--tag) tag="$2" ; shift 2 ;;

+		-c|--compression) compression="$2" ; shift 2 ;;

+		-C|--no-compression) compression="none" ; shift 1 ;;

 		-h|--help) usage ;;

 		--) shift ; break ;;

 	esac

@@ -35,6 +38,18 @@ script="$1"

 [ "$script" ] || usage

 shift

+if [ "$compression" == "auto" ] || [ -z "$compression" ]

+then

+	compression="xz"

+fi

+

+if [ "$compression" == "none" ]

+then

+	compression=""

+else

+	compression=".${compression}"

+fi

+

 if [ ! -x "$scriptDir/$script" ]; then

 	echo >&2 "error: $script does not exist or is not executable"

 	echo >&2 "  see $scriptDir for possible scripts"

@@ -71,18 +86,18 @@ nameserver 8.8.8.8

 nameserver 8.8.4.4

 EOF

-tarFile="$dir/rootfs.tar"

+tarFile="$dir/rootfs.tar${compression}"

 touch "$tarFile"

 (

 	set -x

-	tar --numeric-owner -cf "$tarFile" -C "$rootfsDir" --transform='s,^./,,' .

+	tar --numeric-owner --create --auto-compress --file "$tarFile" --directory "$rootfsDir" --transform='s,^./,,' .

 )

 echo >&2 "+ cat > '$dir/Dockerfile'"

-cat > "$dir/Dockerfile" <<'EOF'

+cat > "$dir/Dockerfile" <<EOF

 FROM scratch

-ADD rootfs.tar /

+ADD $tarFile /

 EOF

 # if our generated image has a decent shell, let's set a default command