#!/bin/bash

# Basic snapshot-style rsync backup script
# https://wiki.archlinux.org/index.php/Rsync

#Path of script
# Absolute path to this script. /home/user/bin/foo.sh
SCRIPT=$(readlink -f "$0")
# Absolute path this script is in. /home/user/bin
SCRIPTPATH=$(dirname "$SCRIPT")

# Config
# ignorelist: https://github.com/rubo77/rsync-homedir-excludes
OPT="-aPh --numeric-ids --no-o --no-g --info=progress2 --exclude-from=${SCRIPTPATH}/ignorelist"
BACKUPS="<Target>"
SRC="<source>/"
SNAP="${BACKUPS}/snapshots/"
LAST="${BACKUPS}/snapshots/last"
LINK="--link-dest=${LAST}"
date=$(date "+%Y-%b-%d:_%T")

mkdir -p "$SNAP"

# run this process with real low priority

ionice -c 3 -p "$$"
renice +12  -p "$$"

# Run rsync to create snapshot
rsync ${OPT} "$LINK" "$SRC" "$SNAP""$date"

# Remove symlink to previous snapshot
rm -f "$LAST"

# Create new symlink to latest snapshot for the next backup to hardlink
ln -s "$SNAP""$date" "$LAST"