backup-script.sh

#!/bin/bash
#
# Backup script for incremental backups to i.e. removable usb drive
# (c) Rickard Armiento, 2005-2025
# Based on the ideas from: http://www.mikerubel.org/computers/rsync_snapshots/
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU Affero General Public License as
#    published by the Free Software Foundation, either version 3 of the
#    License, or (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU Affero General Public License for more details.
#
#    You should have received a copy of the GNU Affero General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#
# NOTE:
#   1. Destination has to be on a file system that supports hardlinks,
#      i.e. Linux ext2/3/4, it will not work on fat32-preformated 
#      usb memory.
#
#   2. The script uses hardlinks between unchanged files to 
#      create what appears as a complete backup for old 
#      dates, while only storing incremental changes.
#
#   3. If you are running out of disk space, you can clean out your
#      old backups manually by just removing directories in the
#      backup tree with rm -rf <name>. However, you only earn the disk 
#      space that corresponds to unique files in that backup. (Read up 
#      on hardlinks if this statement confuses you.)
#
#   4. Make sure the date on your computer is correct before 
#      running this script.
#

##################### CONFIG ####################

## BACKUP_SOURCE
## Absolute path to directory to be backed up

BACKUP_SOURCES=/storage/home/*

## BACKUP_DEST
## Absolute directory path to backup to

BACKUP_DEST_MAIN="/storage/backup/home"

## Date format for backup directory names (see manpage for date)
## ISO: "%Y-%m-%d"
## US:  "%m.%d.%Y"

DATE_FORMAT="%Y-%m-%d"
#DATE_FORMAT="%m.%d.%Y"

###################################################

#### Max number of days to keep files in different categories
MAX_DAILY=7
MAX_WEEKLY=32
MAX_MONTHLY=366

#### Best practices
set -e
set -u
cd /tmp
unset PATH

LS=/bin/ls
RSYNC=/usr/bin/rsync
CP=/bin/cp
FIND=/usr/bin/find
TAIL=/usr/bin/tail
HEAD=/usr/bin/head
TOUCH=/bin/touch
DATE=/bin/date
MKDIR=/bin/mkdir
RM=/bin/rm
MV=/bin/mv
BASENAME=/usr/bin/basename

if [ ! -x "$LS" -o ! -x "$RSYNC" -o ! -x "$CP" -o ! -x "$FIND" -o ! -x "$TAIL" -o ! -x "$TOUCH" -o ! -x "$DATE" -o ! -x "$MKDIR" -o ! -x "$RM" -o ! -x "$MV" -o ! -x "$BASENAME" ]; then
    echo "Some binaries seems to be missing." >&2
    exit 1
fi

#### Check and set lockfile.
if [ -e "${BACKUP_DEST_MAIN}/backup_lockfile" ]; then
    echo "Lockfile exists: ${BACKUP_DEST_MAIN}/backup_lockfile" >&2
    echo "Another backup may already be running, make sure it is not so," >&2
    echo "then delete the lockfile." >&2
    exit 1
fi

trap "$RM -f \"${BACKUP_DEST_MAIN}/backup_lockfile\"; exit" INT TERM EXIT
$TOUCH "${BACKUP_DEST_MAIN}/backup_lockfile"

for BACKUP_SOURCE in $BACKUP_SOURCES; do
    
    USERNAME=$($BASENAME "$BACKUP_SOURCE")
    BACKUP_DEST="$BACKUP_DEST_MAIN/$USERNAME"

    #### Check that source and destination directories exist.
    if [ ! -d "${BACKUP_SOURCE}" ]; then
	echo "Script weirdness: was given $BACKUP_SOURCE to backup, but the directory does not exist." >&2
	continue
    fi

    if [ ! -d "${BACKUP_DEST}" ]; then
	$MKDIR -p "${BACKUP_DEST}"
    fi

    #### Create backup subdirectories if they do not exist.
    $MKDIR -p "${BACKUP_DEST}/Daily" 
    $MKDIR -p "${BACKUP_DEST}/Weekly" 
    $MKDIR -p "${BACKUP_DEST}/Monthly"
    $MKDIR -p "${BACKUP_DEST}/Yearly"

    echo "Starting backup script at $($DATE)."

    echo "Handle 'Previous' directory."

    #### Handle 'Previous' directory
    if [ -d "${BACKUP_DEST}/Previous" ]; then
	PREVIOUS_DATE=$($DATE -r "${BACKUP_DEST}/Previous" +${DATE_FORMAT})
	if [ ! -d "${BACKUP_DEST}/Daily/${PREVIOUS_DATE}" ]; then
	    $MV "${BACKUP_DEST}/Previous" "${BACKUP_DEST}/Daily/${PREVIOUS_DATE}"
	else
	    $RM -rf "${BACKUP_DEST}/Previous" 
	fi
    fi

    echo "Cleaning out daily backups."

    #### Clean daily backups
    while [ 0 == 0 ]; do
        # Find oldest daily backup
	OLDEST_DAILY=$($LS "${BACKUP_DEST}/Daily" -1t | $TAIL -1)
        # Check if it is older than MAX_DAILY days old
	if [ -d "${BACKUP_DEST}/Daily/${OLDEST_DAILY}" ]; then
	    IS_OLD=$($FIND "${BACKUP_DEST}/Daily/${OLDEST_DAILY}" -maxdepth 0 -mtime +$MAX_DAILY)
	    if [ ! -z "${IS_OLD}" ]; then
                # Find its week number
		NEW_WEEKNBR="$((1 + $($DATE -r "${BACKUP_DEST}/Daily/${OLDEST_DAILY}" +'%_d') / 7))"
                # Find most recent weekly backup
		YOUNGEST_WEEKLY=$($LS "${BACKUP_DEST}/Weekly" -1t | $HEAD -1)
		if [ ! -z "${YOUNGEST_WEEKLY}" -a -d "${BACKUP_DEST}/Weekly/${YOUNGEST_WEEKLY}" ]; then
		    OLD_WEEKNBR="$((1 + $($DATE -r "${BACKUP_DEST}/Weekly/${YOUNGEST_WEEKLY}" +'%_d') / 7))"
		    if [ "${NEW_WEEKNBR}" -eq "${OLD_WEEKNBR}" ]; then
	            #We already have a backup from this week
			$RM -rf "${BACKUP_DEST}/Daily/${OLDEST_DAILY}"
			continue
		    fi
		fi
		$MV "${BACKUP_DEST}/Daily/${OLDEST_DAILY}" "${BACKUP_DEST}/Weekly/"
		continue
	    fi
	fi
	break
    done

    echo "Cleaning out weekly backups."

    #### Clean weekly backups
    while [ 0 == 0 ]; do
        # Find oldest weekly backup
	OLDEST_WEEKLY=$($LS "${BACKUP_DEST}/Weekly" -1t | $TAIL -1)
        # Check if it is older than MAX_WEEKLY days old
	if [ -d "${BACKUP_DEST}/Weekly/${OLDEST_WEEKLY}" ]; then
	    IS_OLD=$($FIND "${BACKUP_DEST}/Weekly/${OLDEST_WEEKLY}" -maxdepth 0 -mtime +$MAX_WEEKLY)
	    if [ ! -z "${IS_OLD}" ]; then
                # Find its month number
		NEW_MONTHNBR="$($DATE -r "${BACKUP_DEST}/Weekly/${OLDEST_WEEKLY}" +'%_m')"
                # Find most recent monthly backup
		YOUNGEST_MONTHLY=$($LS "${BACKUP_DEST}/Monthly" -1t | $HEAD -1)
		if [ ! -z "${YOUNGEST_MONTHLY}" -a -d "${BACKUP_DEST}/Monthly/${YOUNGEST_MONTHLY}" ]; then
		    OLD_MONTHNBR="$($DATE -r "${BACKUP_DEST}/Monthly/${YOUNGEST_MONTHLY}" +'%_m')"
		    if [ "${NEW_MONTHNBR}" -eq "${OLD_MONTHNBR}" ]; then
	            # We already have a backup from this month
			$RM -rf "${BACKUP_DEST}/Weekly/${OLDEST_WEEKLY}"
			continue
		    fi
		fi
		$MV "${BACKUP_DEST}/Weekly/${OLDEST_WEEKLY}" "${BACKUP_DEST}/Monthly/"
		continue
	    fi
	fi
	break
    done

    echo "Cleaning out monthly backups."

    #### Clean monthly backups
    while [ 0 == 0 ]; do
        # Find oldest monthly backup
	OLDEST_MONTHLY=$($LS "${BACKUP_DEST}/Monthly" -1t | $TAIL -1)
        # Check if it is older than MAX_MONTHLY days old
	if [ -d "${BACKUP_DEST}/Monthly/${OLDEST_MONTHLY}" ]; then
	    IS_OLD=$($FIND "${BACKUP_DEST}/Monthly/${OLDEST_MONTHLY}" -maxdepth 0 -mtime +$MAX_MONTHLY)
	    if [ ! -z "${IS_OLD}" ]; then
                # Find its year number
		NEW_YEARNBR="$($DATE -r "${BACKUP_DEST}/Monthly/${OLDEST_MONTHLY}" +'%Y')"
                # Find most recent yearly backup
		YOUNGEST_YEARLY=$($LS "${BACKUP_DEST}/Yearly" -1t | $HEAD -1)
		if [ ! -z "${YOUNGEST_YEARLY}" -a -d "${BACKUP_DEST}/Yearly/${YOUNGEST_YEARLY}" ]; then
		    OLD_YEARNBR="$($DATE -r "${BACKUP_DEST}/Yearly/${YOUNGEST_YEARLY}" +'%Y')"
		    if [ "${NEW_YEARNBR}" -eq "${OLD_YEARNBR}" ]; then
	                # We already have a backup from this year
			$RM -rf "${BACKUP_DEST}/Monthly/${OLDEST_MONTHLY}"
			continue		    
		    fi
		fi
		$MV "${BACKUP_DEST}/Monthly/${OLDEST_MONTHLY}" "${BACKUP_DEST}/Yearly/"	    
		continue
	    fi
	fi
	break
    done

    if [ -e "${BACKUP_DEST}/Current" ]; then
	$MV "${BACKUP_DEST}/Current" "${BACKUP_DEST}/Previous"
    fi

    if [ ! -e "${BACKUP_DEST}/Current" ]; then
	$MKDIR -p "${BACKUP_DEST}/Current"
    fi

    if [ -d "${BACKUP_DEST}/Previous" ]; then
	echo "Backing up changed files."
	$RSYNC -a --delete --link-dest="${BACKUP_DEST}/Previous" "${BACKUP_SOURCE}/" "${BACKUP_DEST}/Current" --exclude "/.ARCHIVE"
    else
	echo "First initial backup."
	$RSYNC -a --delete "${BACKUP_SOURCE}/" "${BACKUP_DEST}/Current" --exclude "/.ARCHIVE" 
    fi

    #### Mark current backup with date when backup finished.
    $TOUCH "${BACKUP_DEST}/Current"
done

#### Touch backup directory with date all backups finished
$TOUCH "$BACKUP_DEST_MAIN"

echo "Backup finished at $($DATE)."