rsync-backup

#!/bin/bash
set -e

# A tool for a versioned backup using only rsync.

# This tool creates a snapshot folder in the destination URL named by the current datetime.
# After synchronizing the selected source folders to the snapshot folder, it creates a symlink
# named `last` pointing to the created snapshot folder. When creating a new snapshot, the files
# from the `last` snapshot that have not changed are automatically hardlinked.

# Since the tool uses only rsync, it is possible to backup to rsync daemon.

if [ $# -lt 2 ]; then
  echo "Usage: $0 src dst"
  echo "Example over ssh: $0 / root@192.168.0.1:/snapshots"
  echo "Example over rsync: $0 / rsync://root@192.168.0.1/snapshots"
  echo "Example local: $0 /home/user /user-snapshots"
  exit 1
fi

# Source folders to be backed up (many system folders, caches, etc., are skipped automatically).
src="${1}"
# Remote server address.
dst="${2}"

# The number of snapshots to keep +1. The +1 is for the symlink to the latest snapshot.
# Set to -1 to diable the pruning of old snapshots.
# Note that using this option requires the destination to be a local folder.
keep=-1
# The name of the symlink to the most recent snapshot.
last="last"
# The name of the new snapshot.
snapshot_name=`date +"%Y%m%d%H%M"`
# rsync options.
rsync_opts="--archive --xattrs --acls"

# ---
# Create a temporary directory and clean it on exit.
# ---
tmpdir="`mktemp -d --tmpdir rsync-backup.XXXXXX`"
echo "Temporary directory: ${tmpdir}"
function cleanup {
    rm -rf "${tmpdir}"
}
trap cleanup INT TERM EXIT

# ---
# Create the snapshot directory in the destination.
# ---
echo "Creating the destination directory ${dst}/${snapshot_name}."
mkdir "${tmpdir}/${snapshot_name}"
rsync --recursive "${tmpdir}/${snapshot_name}" "${dst}"

# ---
# Sync the snapshot.
# ---
echo "Syncing snapshot to ${dst}/${snapshot_name}."
exit_code=0
rsync ${rsync_opts} \
      --link-dest="../${last}" \
      --exclude="${tmpdir}/*" \
      --exclude="${dst}/*" \
      --exclude={"/dev/*","/proc/*","/sys/*","/swapfile","/tmp/*"} \
      --exclude={"/run/*","/mnt/*","/media/*","/lost+found"} \
      --exclude={"/bin/*","/lib*/*","/opt/*","/sbin/*"} \
      --exclude={"/usr/bin/*","/usr/lib*/*","/usr/share/*","/usr/include/*","/usr/src/*"} \
      --exclude={"/var/log/*","/var/cache/*"} \
      --exclude={"*~","~*"} \
      --exclude={"/home/*/.cache/*","/home/*/.local/*"} \
      --exclude={"*/.Trash/*","*/.Trash-*"} \
      ${src}/ "${dst}/${snapshot_name}" || exit_code=$?
# Allow errors caused by vanished source files.
if [ "${exit_code}" -ne 0 ] && [ "${exit_code}" -ne 24 ]; then
    echo "Rsync failed with error code ${error_code}."
    exit ${error_code}
fi

# ---
# Create the link to the latest snapshot.
# ---
echo "Creating the symlink to the latest snapshot."
ln -s "${snapshot_name}" "${tmpdir}/${last}"
rsync --links --progress "${tmpdir}/${last}" "${dst}"

# ---
# Remove old snapshots (this requires the remote system to be mounted).
# ---
# This should be done last to avoid the loss of valid backups when rsync fails
# multiple times.
if [ "${keep}" -gt -1 ]; then
    for dir in `ls -1d "${dst}"/* | head -n -"${keep}"`; do
        echo "Removing old snapshot ${dir}."
        rm -rf "${dir}"
    done
fi