SOWN Backup

This is SOWN's backup system, currently deployed on backup-b32-1 and backup-b53-1. On those servers you can find all backups in /data, with snapshots exposed in /data/{hostname}/.zfs/snapshots/.

It automatically takes backups of all hosts in Netbox with the Backup tag, doing the following:

• creating a zfs dataset data/{hostname}
• rsyncing the server's rootfs to there
  • excluding a list of standard files/directories in excludes.py
  • excluding any files/directories listed in /etc/backup-exclude.conf on the server being backed up
• taking and rotating ZFS snapshots at regular intervals, keeping as many as are needed per config.py
• notifying Icinga about backup completion via passive checks

Operational notes

Logs

All logs go to syslog, and when running from cron, errors will be emailed to SOWN.

To get full logs from journald:

root@backup:~# journalctl -e _COMM=backup

Manually taking a backup

About to do something dangerous? You can manually kick off a backup and a snapshot to make sure it's kept. Eg:

root@backup:~# backup --quiet vpn
root@backup:~# zfs snapshot data/vpn@tds-before-18.04-upgrade

(skip the --quiet if you want to see logs as the backup takes place)

To delete a snapshot you made by hand:

root@backup:~# zfs destroy data/vpn@tds-before-18.04-upgrade

Internal details

Hook scripts

Before running a backup, all executable files in /etc/backup-scripts/ will be run via run-parts.

Hook scipts should confirm success via exit codes - if a non-zero exit code is returned, the backup script will generate an error (which will turn into a cron mail and an icinga alert). As there are multiple backup servers that run independently, hook scripts also need to be able to cope with being run multiple times at once.

/var/lib/backup/ is created by ansible and is a safe place to store backup files so they will only be readable by root. Any backup scripts that are used on multiple servers should be deployed via ansible.

A simple example:

#!/bin/bash
set -eo pipefail
# back up the date, very important!
date > /var/lib/backup/date.$$
mv /var/lib/backup/date.$$ /var/lib/backup/date

Installing

Before starting, you'll need a zfs pool called data. Eg on an ubuntu install, using an LVM LV for the backing block device:

root@backup:~# apt install zfsutils-linux
root@backup:~# zpool create -o ashift=12 -O compression=lz4 data /dev/ubuntu-vg/data

Then clone the repo, create a virtual environment and install it:

root@backup:~# mkdir -p /opt/sown
root@backup:~# git -C /opt/sown/ clone git@github.com:sown/backup.git
root@backup:~# cd /opt/sown/backup/
root@backup:/opt/sown/backup# python3 -m venv venv
root@backup:/opt/sown/backup# ./venv/bin/pip3 install .

Write a config:

root@backup:/opt/sown/backup# cp backup/config.example.py backup/config.py
root@backup:/opt/sown/backup# vim backup/config.py 

You can then run it like so:

root@backup:/opt/sown/backup# ./venv/bin/backup 

To make the "backup" command work system-wide:

root@backup:/opt/sown/backup# ln -rs ./venv/bin/backup /usr/local/bin/

Once everything is up and running, add something like this to root's crontab:

# nightly backup
@daily /opt/sown/backup/venv/bin/backup --quiet all

Developing

As the module is installed in editable mode, you can work on the source directly. To add dependencies, edit pyproject.toml, and run poetry update.

Poetry is used to manage dependencies, and you will need it to update or add dependencies.

You do not need poetry to install the tool or develop it.

Linting

We use ruff to ensure that our code meets the PEP 8 standards.

Execute the linter: make lint

Static Type Checking

We use mypy to statically type check our code.

Execute Type Checking: make type