Incremental backup using snapshots

[tony-travis]

This is a simple ETOH (Enhanced Towers of Hanoi) backup for LizardFS/SaunaFS/LeilFS

#!/bin/bash
#@(#)backup  2026-04-13  A.J.Travis

#
# simple rsync backup to SaunaFS with snapshots
#

# trap errors
#set -e
set -u

# source configuration file
CONFIG="/etc/default/$(basename $0)"
if [ -r $CONFIG ]; then
    . $CONFIG
fi

# filesystems to backup
filesystems=$(echo ${FILESYSTEMS:-"/ /opt /home"})

export PATH=/sbin:/bin:/usr/sbin:/usr/bin
export backup="/$(basename $0)"
export host=$(hostname)

# abort if backup is in use
if [ "$(grep -w $backup /proc/mounts)" ]; then

	# try to unmount /backup
	umount $backup
	if [ "$(grep -w $backup /proc/mounts)" ]; then
		echo "$backup in use - backup aborted"
		exit 1
	fi
fi

# mount backup
mount $backup 
if [ ! "$(grep -w $backup /proc/mounts)" ]; then
        echo "Can't mount $backup - backup aborted"
        exit 1
fi

# get the date (day 1 is Monday)
day=$(date +%u)
month=$(date +%m)
dom=$(date +%d)

# dump level
if [ -n "$*" ]; then

    # set on command line
    level="$1"
else

    # Quarterly Enhanced Towers of Hanoi
    if [ $day == "7" ]; then
        if [ $dom -le 7 ]; then
            case $month in
            "01" | "04" | "07" | "10") level=0 ;;
            *) level=1 ;;
        esac
        elif [ $dom -le 14 ]; then
            level=3
        elif [ $dom -le 21 ]; then
            level=2
        elif [ $dom -le 28 ]; then
            level=4
        elif [ $dom -le 31 ]; then
            level=3
        fi
    else
        case $day in
        "1") level=6 ;;
        "2") level=5 ;;
        "3") level=8 ;;
        "4") level=7 ;;
        "5") level=9 ;;
        "6") level=8 ;;
        esac
    fi
fi

# check level-zero backup exists
if [ ! -d $backup/$host/0 ]; then

	# force level zero backup
	mkdir -p $backup/$host/0
	level=0
fi

# sync to level-zero backup
cmd="rsync --exclude=/tmp --exclude=/var/tmp --stats --delete -axH ${filesystems} $backup/$host/0"
echo $cmd; $cmd

# time and date stamp level-zero backup
touch $backup/$host/0

# replace existing snapshot
if [ $level -ne 0 ]; then
       	if [ -d $backup/$host/$level ]; then

		# force immediate removal by setting zero trashtime		
		saunafs settrashtime -r 0 $backup/$host/$level
		saunafs rremove $backup/$host/$level
		if [ -d $backup/$host/$level ]; then
			echo "backup: failed to remove $backup/$host/$level"
			exit 1
		fi
	fi
	saunafs makesnapshot $backup/$host/0 $backup/$host/$level

	# time and date stamp snapshot
	touch $backup/$host/$level
fi

# unmount backup carefully
sync;sync
umount $backup