Add attach commands for losetup

bin/losetup-mount

@@ -0,0 +1,36 @@
+#!/bin/bash
+# readies a VHD device in Linux
+# nbd-mount /path/to/vhd /dev/nbd0
+APP_DIR="$(dirname "$0")"
+DRIVE="$1"
+DISK_LABEL="$2"
+DISK_PATH="/dev/disk/by-label/$DISK_LABEL"
+SLEEP_INTERVAL=0.5
+
+# refuse to connect twice
+EXISTING_DRIVE="$(losetup -l | tail -n +2 | tr -s ' ' | cut -f 6 | grep -w "$DRIVE")"
+if [ -n "$EXISTING_DRIVE" ]; then
+	EXISTING_LOOP="$(losetup -l | tail -n +2 | tr -s ' ' | grep -w "$DRIVE" | cut -f 1 -d ' ')"
+	if ! [ -L "$DISK_PATH" ] || ! [ -b "$DISK_PATH" ]; then
+		echo "$DRIVE already mounted to $EXISTING_LOOP"
+		exit 1
+	fi
+	LOOP_DEST="$(readlink -f $DISK_PATH)"
+	if [ "$LOOP_DEST" != "$EXISTING_LOOP" ]; then
+		echo "$DRIVE already mounted to $EXISTING_LOOP"
+		exit 1
+	fi
+
+	# it's already mounted to the same destination
+	exit 0
+fi
+
+# wait for device to appear
+if ! [ -e "$DISK_PATH" ]; then
+	losetup -f "$DRIVE"
+
+	# poll until the block device node appears or task times out
+	until [ -L "$DISK_PATH" ] && [ -b "$DISK_PATH" ]; do
+		sleep "$SLEEP_INTERVAL"
+	done
+fi