#!/bin/bash
#
#  This is a dump script from "info tar"
#  with lots of modifications.
#
#   Lots of help from info bash and from the web pages
#    http://www.student.nada.kth.se/~d96-jja/bash/bashtut.html
#    http://www.gnu.org/manual/bash/html_mono/bashref.html
#   Warning!   \ then space at the end of a line causes no end of problems
#
#  example recovery (done as root):
#
#    cd /backup
#    tar zxvf  dump0.tgz --listed-incremental dump0.inc home/bvds
#    tar zxvf  dump1.tgz --listed-incremental dump1.inc home/bvds
#    tar zxvf  dump2.tgz --listed-incremental dump2.inc home/bvds
#
#
#  Files to back up
#
files="/home /etc /usr/local"
#
#  Directory to put backups in
#
mntdir="/mnt/jephthah"
dir="/mnt/jephthah/backup"
#
#  Backup rate (seconds)
#  This allows the script to be called at a more
#  frequent rate than the desired backup rate.
#
updaterate=$((3600*24))
#
#  If the machine with the backup directory has
#  been rebooted, then the nfs volume becomes readonly.
#
mount $mntdir
#
#  file with number of backups performed on top of 
#  current level 0 dump.
#
countfile="${dir}/dump.cnt"
#
#
notifysendexists(){
    command -v notify-send > /dev/null;
}
#
# Determine if there is a currently running dump
#
if [ -e ${dir}/in-progress ]; then
    PID=`cat ${dir}/in-progress`
    if ps -p ${PID} > /dev/null
    then
	echo "Previous backup still running, PID=${PID}, exiting."
	exit 0
    fi
fi
#
# Count number of dumps and find level
#
if [ $# -eq 0 ]; then
    if [ -e $countfile ]; then
	# Test if last update is too recent
	age=$(($(date +%s) - $(stat $countfile -c %Y)))
	if [ $age -lt $updaterate ]; then
	    echo "Last update $age seconds ago, exiting."
	    umount $mntdir
	    exit 0
	fi
	count=$(( $(cat $countfile) + 1 ))
	level=0
	j=$count
	until [ $j -eq 0 ]; do
	    level=$(( $level+(j&1) ))
	    j=$(( j>>1 ))
	    #      echo "In loop, level is $level."
	done
    else
	echo "Can't find file $countfile, exiting."
	exit 666
    fi
else
    level=$1
    count=$(( (1<<$level) -1 ))
fi
#
echo "Starting level $level dump, dump number $count"
notifysendexists && notify-send "Disk backup" "Starting level $level dump, dump number $count." -u normal
#
# Move older copies to backup directory
# This moves all files at the present level and higher
#
if [ ! -d ${dir}/backback ]; then mkdir ${dir}/backback; fi
if [ ! -d ${dir}/back ]; then mkdir ${dir}/back; fi
#
#  Don't move files if last attempt was not completed.
i=$level
while [ -e ${dir}/dump${i}.tgz ] && [ ! -e ${dir}/in-progress ]; do
    if [ -e ${dir}/back/dump${i}.tgz ]; then
	mv ${dir}/back/dump${i}.* ${dir}/backback
	echo "  moving ${dir}/back/dump${i}.* to ${dir}/backback"
    fi
    mv ${dir}/dump${i}.* ${dir}/back
    echo "  moving ${dir}/dump${i}.* to ${dir}/back"
    i=$(( i+1 ))
done
#
#
#  For dump levels higher than zero, find previous
#  snapshot file and copy it.
#
if [ $level -ne 0 ]; then
    datfile=${dir}/dump$(( $level -1 )).inc
    if [ -e $datfile ]; then
	cp $datfile ${dir}/dump${level}.inc
    else
	echo "Snapshot file $datfile doesn't exist, exiting."
	exit 1
    fi
fi
#
#  Handle case where backup is interrupted.
echo "$$" > ${dir}/in-progress
#
#  perform tar using snapshot file
#
#  turned off verbose -v
#  Exit on failed write, allow failed read.
#
if tar --ignore-failed-read -z -c \
       -f ${dir}/dump${level}.tgz\
       --label="User dump on date $(date)"\
       --listed-incremental=$dir/dump${level}.inc\
       ${files}
then
    #
    #  save count in count file
    #
    rm ${dir}/in-progress
    echo $count > $countfile
    echo "  backup completed."
    notifysendexists && notify-send "Disk backup" "Backup completed" -u normal
else
    echo "  backup failed, error ${ERRCODE}, exiting"
    notifysendexists && notify-send "Disk backup" "Backup failed" -u normal
    exit $ERRCODE
fi
#
# We don't want users to read the dump files
#
chmod 600 ${dir}/dump${level}.tgz
chmod 600 ${dir}/dump${level}.inc
#
umount $mntdir
#