backup.sh

#!/bin/bash

# A backup solution based on rsync with hard links and no deletion of old images
# Deletion would be delegated to a script such as weeder
# https://pypi.org/project/weeder/

set -euo pipefail
set -x

dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

backup_source=root@nas
base_dir=/mnt/nasbkp/volume1
identity_key=~piro/.ssh/id_rsa-nasbkp
rsync_opts="--archive --hard-links --one-file-system --numeric-ids \
    --exclude-from=${dir}/volume1.exclude --delete --delete-excluded"

# Verbosity
# rsync_opts="${rsync_opts} --info=progress2"
rsync_opts="${rsync_opts} -v"

# check if there is an interrupted backup or create a new backup dir
backup_dir=$(ls -1d "${base_dir}"/????????_????.tmp 2>/dev/null | head -1 || true)
if [ -z "${backup_dir}" ]; then
    echo "creating a backup into ${backup_dir}"
    backup_dir="${base_dir}/$(date +%Y%m%d_%H%M).tmp"
else
    echo "continuing a backup already started into ${backup_dir}"
fi

# check if there is a previous dir to link
previous_dir=$(ls -1dr "${base_dir}"/????????_???? 2>/dev/null | head -1 || true)
if [ -n "${previous_dir}" ]; then
    echo "hard-linking from ${previous_dir}"
    rsync_opts="${rsync_opts} --link-dest=${previous_dir}"
fi

# Run an ssh agent if there isn't one already. Close it on leaving.
if [ -z "${SSH_AGENT_PID:-}" ]; then
    eval `/usr/bin/ssh-agent`
    trap 'eval `/usr/bin/ssh-agent -k`' 0
fi

# Load the identity file if not already there.
if ! ssh-add -l | grep -q $(ls ${identity_key}); then
    ssh-add "${identity_key}"
fi

# copy files over
mkdir -p "${backup_dir}"
rsync ${rsync_opts} "${backup_source}": "${backup_dir}"

# copy successful: remove the tmp status
mv -v ${backup_dir} ${backup_dir/.tmp/}