Use a random temp directory for mounting

This allows using the script multiple times in parallel on different
disks.

To prevent all these directories littering the filesystem, an exit
handler is registered to remove them again when the script exits (also
unmounting any mounted filesystems just in case).

Author: matthijskooijman

rpi-clone

@@ -85,8 +85,6 @@ then
 	apt-get install -y --no-install-recommends $need_packages
 fi
 
-export clone=/mnt/clone
-export clone_src=/mnt/clone-src
 export clone_log=/var/log/$PGM.log
 
 HOSTNAME=`hostname`
@@ -993,15 +991,25 @@ then
 	exit 0
 fi
 
-if [ ! -d $clone ]
-then
-	mkdir $clone
-fi
-if [ ! -d $clone_src ]
+export clone=$(mktemp --tmpdir --directory rpi-clone-dst.XXXXXX)
+export clone_src=$(mktemp --tmpdir --directory rpi-clone-src.XXXXXX)
+
+if ! [ -n "$clone" -a -d "$clone" -a -n "$clone_src" -a -d "$clone_src" ]
 then
-	mkdir $clone_src
+	echo "Failed to create temporary mount directories"
+	echo "Aborting!"
+	exit 1
 fi
 
+# Make sure we cleanup on exit, regardless of how we exit
+cleanup() {
+	umount "$clone" 2> /dev/null
+	umount "$clone_src" 2> /dev/null
+	rmdir "$clone"
+	rmdir "$clone_src"
+}
+trap cleanup EXIT
+
 # dst_mount_flag enumerations:
 live=1
 temp=2