#!/bin/bash

# from: http://www.system-rescue-cd.org/Sysresccd-manual-en_LVM_Making-consistent-backups-with-LVM

VOLGROP='systemvg'               # name of the volume group
ORIGVOL='rootlv'                 # name of the logical volume to backup
SNAPVOL='snaplv'                 # name of the snapshot to create
SNAPSIZ='-l 100%FREE'            # ex. '-L 4G' space to allocate for the snapshot in the volume group
FSAOPTS='-z4 -j2 -s45000 -c -'   # options to pass to fsarchiver
BACKDIR='/mnt/hdd/backup'        # where to put the backup
BACKNAM='rootlv'                 # name of the archive

# ----------------------------------------------------------------------------------------------

PATH="${PATH}:/usr/sbin:/sbin:/usr/bin:/bin"
TIMESTAMP="$(date +%Y%m%d-%Hh%M)"

{

# only run as root
if [ "$(id -u)" != '0' ]
then
    echo "this script has to be run as root"
    exit 1
fi

# check that the snapshot does not already exist
if [ -e "/dev/${VOLGROP}/${SNAPVOL}" ]
then
    echo "the lvm snapshot already exists, please destroy it by hand first"
    exit 1
fi

echo ${BACKNAM}-${TIMESTAMP}
echo "========================================================"

# create the lvm snapshot
echo "creating lvm snapshot ${SNAPVOL}..."
if ! lvcreate -v -s ${SNAPSIZ} -n ${SNAPVOL} /dev/${VOLGROP}/${ORIGVOL}
then
    echo "creation of the lvm snapshot failed"
    exit 1
fi

# decrypt snapshot
echo "decrypting snapshot into ${VOLGROP}-${SNAPVOL}_crypt..."
if ! cryptsetup -v luksOpen /dev/${VOLGROP}/${SNAPVOL} ${VOLGROP}-${SNAPVOL}_crypt
then
    echo "decrypt snapshot volume failed"
    exit 1
fi

# main command of the script that does the real stuff
echo "creating archive folder..."
mkdir ${BACKDIR}/${BACKNAM}-${TIMESTAMP}

echo "archiving snapshot to ${BACKDIR}/${BACKNAM}-${TIMESTAMP}/..."
if fsarchiver -v savefs ${FSAOPTS} ${BACKDIR}/${BACKNAM}-${TIMESTAMP}/${BACKNAM}-${TIMESTAMP}.fsa /dev/mapper/${VOLGROP}-${SNAPVOL}_crypt
then
    echo "fsarchiver finished successfully"
    #find "${BACKDIR}/${BACKNAM}-${TIMESTAMP}" -name "${BACKNAM}-${TIMESTAMP}.f*" -exec md5sum "{}" + > ${BACKDIR}/${BACKNAM}-${TIMESTAMP}/md5checklist.chk
    for i in $(find "${BACKDIR}/${BACKNAM}-${TIMESTAMP}" -name "${BACKNAM}-${TIMESTAMP}.f*")
    do
        echo "calculating md5 for $i"
        md5sum $i >> ${BACKDIR}/${BACKNAM}-${TIMESTAMP}/md5checklist.chk
        echo "md5 done"
    done
    RES=0
else
    echo "fsarchiver failed"
    RES=1
fi

# close luks
echo "closing encrypted volume..."
if ! cryptsetup -v luksClose /dev/mapper/${VOLGROP}-${SNAPVOL}_crypt
then
    echo "cannot close encrypted snapshot volume"
    RES=1
fi

# remove the snapshot
echo "removing snapshot..."
if ! lvremove -f /dev/${VOLGROP}/${SNAPVOL}
then
    echo "cannot remove the lvm snapshot"
    RES=1
fi

echo "done. status=${RES}"
exit ${RES}

# variable ${TIMESTAMP} does not work in tee for some reason
} 2>&1 | tee "${BACKDIR}/session.log"