utils/elm-mgmt.sh

#!/sbin/bash

# Steamline use of backup external hardrive.
#
# The backup hard drive is assumed to encrypted using cryptsetup luks mode.
# The script is used to issue the desired command on mount and umount.
# Two modes are available : mount and umount
#
# Mount mode :
# Issue the crypt setup command and then mount the then created mapper. Default behavior is to assume a fstab entry exists and mount behaves correctly. If the mountpoint in fstab doesn't exists, it is created
#
# Umount mode:
# Umounts the mapper, closes the cryptsetup device and then 
# Mount is used to issue the cryptsetup
# This script is meant to be run as root

# Script fails if any command fails
set -e

DEVICE=
UMOUNTMODE=0
MOUNTMODE=0

print_help() {
	echo "elm-mgmt [OPTIONS…]"
	echo ""
	echo "Script managing Elm, an external hard drive for backups. The device is assumed to be a LUKS encrypted device."
	echo ""
	echo "You need to specify the disk and partition to be opened and mounted. This can be achieve via command line option -i and -p or thourgh environment variables:"
	echo "	- BACKUP_DEVICE_UUID, the UUID of the disk that will be open with cryptsetup, assumed to be a LUKS device."
	echo "	- BACKUP_PART_UUID, the UUID of the partition to be mounted of the device."
	echo ""
	echo "-c, --cryptname NAME		Call the mapped device NAME when opening the LUKS partition."
	echo "-d, --device DEVICE		Path DEVICE to the device where reside the LUKS partition."
	echo "-h, help			Print this help message."
	echo "-m, --mount			Mount mode: open the LUKS device and mount the partition. This is the default behavior."
	echo "-u, --umount			Umount mode: un-mounts the partition, close the LUKS device and instruct the disk to spin down using hdparm."
	echo ""
	echo "EXIT CODES"
	echo "0		Successfully made the requested operation."
	echo "1		An error occured."
	echo "2		Impossible to find the device."
	echo "124		Test exit code."
}

while [ $# -gt 0 ]
do
	case $1 in
		-d|--device)
			DEVICE="$2"
			shift # past argument
			if [ $# -eq 0 ]; then
				echo "You must specify a device"
				exit 1
			fi
			shift # past value
			;;
		-h|--help)
			print_help
			exit 0
			;;
		-i|--disk-uuid)
			shift # pass argument
			BACKUP_DEVICE_UUID="$1"
			shift # pass value
			;;
		-p|--part-uuid)
			shift # pass argument
			BACKUP_PART_UUID="$1"
			shift # pass value
			;;
		-m|--mount)
			MOUNTMODE=1
			shift # pass argument
			;;
		-u|--umount)
			UMOUNTMODE=1
			shift # pass argument
			;;
		-c|cryptname)
			CRYPTNAME="$2"
			shift # pass argument
			if [ $# -eq 0 ]; then
				echo "You must specify the name of the crypt mapping"
				exit 1
			fi
			shift # pass value
			;;
		-*|--*)
			echo "Unknown option $1"
			exit 1
			;;
		*)
			echo "Extra useless argument: $1"
			exit 1
			;;
	esac
done

if [ -z "$BACKUP_DEVICE_UUID" ]
then
	echo "No backup disk UUID specified, stopping"
	print_help
	exit 31
fi

if [ -z "$BACKUP_PART_UUID" ]
then
	echo "No backup part UUID specified, stopping"
	print_help
	exit 32
fi

BACKUP_DEVICE_PATH="/dev/disk/by-uuid/$BACKUP_DEVICE_UUID"
MAPPER_PATH="/dev/disk/by-uuid/$BACKUP_PART_UUID"
if [ -z "$CRYPTNAME" ]
then
	CRYPTNAME="crypt-$BACKUP_DEVICE_UUID"
fi

if [ "$MOUNTMODE" -eq 0 ] && [ "$UMOUNTMODE" -eq 0 ]
then
	MOUNTMODE=1
fi

if [ -z "$DEVICE" ]
then
	DEVICE_NAME=$(lsblk -o UUID,NAME | awk -v uuid="$BACKUP_DEVICE_UUID" '$1 == uuid {print $2}')
	DEVICE="/dev/$DEVICE_NAME"
	if [ -z "$DEVICE" ]
	then
		echo "Couldn't find device with UUID: $BACKUP_DEVICE_UUID"
		exit 1
	fi
else
	LUKS_UUID=$(lsblk -Adno UUID /dev/sda)
	echo "Found UUID: $LUKS_UUID"
	exit 124
fi

if [ ! -b "$DEVICE" ]
then
	echo "Device doesn't exists or isn't a block device: $DEVICE"
	exit 0
fi

if [ "$MOUNTMODE" -eq 1 ]
then
	echo "Mount mode…"
	# To be conservative and to less tests, start by checking if the device is already mounted
	MOUNT_POINT=$(lsblk -o UUID,MOUNTPOINT | awk -v uuid="$BACKUP_PART_UUID" '$1 == uuid {print $2}')
	if [ -n "$MOUNT_POINT" ]
	then
		echo "device opened and mapper mounted, nothing to do, exiting"
		exit 0
	fi
	IS_LUKS=$(cryptsetup isLuks "$BACKUP_DEVICE_PATH")
	if [ ! IS_LUKS ]
	then
		echo "Device $LUKS_UUID is not a LUKS device"
		exit 1
	else
		echo "Device $LUKS_UUID is a luks device"
	fi
	# Check that Elm is available
	if [ ! -b "$BACKUP_DEVICE_PATH" ]
	then
		echo "Error: couldn't find disk $BACKUP_DEVICE_UUID"
		echo "Maybe backup disk isn't appear to be plugged in"
		exit 1
	else
		echo "Backup device found"
	fi
	# Check if the luks device is already opened
	if [ -b "/dev/disk/by-uuid/$BACKUP_PART_UUID" ]
	then
		echo "LUKS device is already opened, continue"
	else
		cryptsetup open --type luks "$BACKUP_DEVICE_PATH" "$CRYPTNAME"
		echo "Device opened successfully"
	fi
	mount -m "$MAPPER_PATH"
	exit 0
elif [ "$UMOUNTMODE" -eq 1 ]
then
	echo "Umount mode"
	umount "/dev/mapper/$CRYPTNAME"
	cryptsetup close "$CRYPTNAME"
	hdparm -y "$DEVICE"
	exit 0
else
	echo "Unknown mode, this shouldn't happen"
	exit 5
fi