Incremental backup using rsync

incremental_backup.sh

#!/bin/bash

# Incremental backup using rsync
# see http://www.mikerubel.org/computers/rsync_snapshots/#Incremental

set -e

BACKUP_DIR=backup

rot_cycle_days=7  # for example
limit=$(($rot_cycle_days-1))

mkdir -p "$BACKUP_DIR.$limit"
mv "$BACKUP_DIR.$limit" "$BACKUP_DIR.tmp"
for i in $(seq 0 $((limit-1))); do
    mkdir -p "$BACKUP_DIR.$((limit-i-1))"
    mv "$BACKUP_DIR.$((limit-i-1))" "$BACKUP_DIR.$((limit-i))"
done
mv "$BACKUP_DIR.tmp" "$BACKUP_DIR.0"

# these cp options not supported on os x
cp --archive --link "$BACKUP_DIR.1/." "$BACKUP_DIR.0"
rsync -a --delete "$BACKUP_DIR/" "$BACKUP_DIR.0/"