rsync --link-dest

rsync-link-dest.sh

#!/bin/bash

set -e

TARGET_DIR=/path/to/target
BACKUP_DIR=/path/to/backup
RSYNC=/usr/bin/rsync
RSYNC_ARGS="-avS --stats --human-readable --delete $CMD_ARGS"
ROTATE=3

today=$(date +%Y%m%d)
yesterday=$(date +%Y%m%d --date="1 days ago")
oldday=$(date +%Y%m%d --date="$ROTATE days ago")

rsync_args=$RSYNC_ARGS

if [ ! -z "$RSYNC_EXCLUDE_FILE" -a -e "$RSYNC_EXCLUDE_FILE" ]; then
        rsync_args="$rsync_args --exclude-from=$RSYNC_EXCLUDE_FILE"
fi

if [ -d "$BACKUP_DIR.$yesterday" ]; then
        rsync_args="$rsync_args --link-dest=../$(dirname $BACKUP_DIR.$yesterday)"
fi

if [ ! -d "$BACKUP_DIR.$today" ]; then
        mkdir "$BACKUP_DIR.$today"
        ln -s "$BACKUP_DIR.$today" $BACKUP_DIR
fi

# rotate
if [ -d "$BACKUP_DIR.$oldday" ]; then
        rm -fr "$BACKUP_DIR.$oldday"
fi

eval $(echo $RSYNC $rsync_args $TARGET_DIR/ $BACKUP_DIR)