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---
title: 'Borg ansible role (continued)'
description: 'The ansible role I rewrote to manage my borg backups'
date: '2024-10-07'
tags:
- ansible
- backups
- borg
---
## Introduction
I initially wrote about my borg ansible role in [a blog article three and a half years ago]({{< ref "borg-ansible-role.md" >}}). I released a second version two years ago (time flies!) and it still works well, but I am no longer using it.
I put down ansible when I got infatuated with nixos a little more than a year ago. As I am dialing it back on nixos, I am reviewing and changing some of my design choices.
## Borg repositories changes
One of the main breaking change is that I no longer want to use one borg repository per host as my old role managed: I want one per job/application so that backups are agnostic from the hosts they are running on.
The main advantages are:
- one private ssh key per job
- no more data expiration when a job stops running on a job for a time
- easier monitoring of job run: now checking if a repository has new data is enough, before I had to check the number of jobs that wrote to it in a specific time frame.
The main drawback is that I lose the ability to automatically clean a borg server's `authorized_keys` file when I completely stop using an application or service. Migrating from host to host is properly handled, but complete removal will be manual. I tolerate this because now each job has its own private ssh key, generated on the fly when the job is deployed to a host.
## The new role
### Tasks
The main.yaml contains:
``` yaml
---
- name: 'Install borg'
package:
name:
- 'borgbackup'
# This use attribute is a work around for https://github.com/ansible/ansible/issues/82598
# Invoking the package module without this fails in a delegate_to context
use: '{{ ansible_facts["pkg_mgr"] }}'
```
It will be included in a `delete_to` context when a client configures its server. For the client itself, this tasks file will run normally and be invoked from a `meta` dependency.
The meat of the role is in the client.yaml:
``` yaml
---
# Inputs:
# client:
# name: string
# jobs: list(job)
# server: string
# With:
# job:
# command_to_pipe: optional(string)
# exclude: optional(list(string))
# name: string
# paths: optional(list(string))
# post_command: optional(string)
# pre_command: optional(string)
- name: 'Ensure borg directories exists on server'
file:
state: 'directory'
path: '{{ item }}'
owner: 'root'
mode: '0700'
loop:
- '/etc/borg'
- '/root/.cache/borg'
- '/root/.config/borg'
- name: 'Generate openssh key pair'
openssh_keypair:
path: '/etc/borg/{{ client.name }}.key'
type: 'ed25519'
owner: 'root'
mode: '0400'
- name: 'Read the public key'
ansible.builtin.slurp:
src: '/etc/borg/{{ client.name }}.key.pub'
register: 'borg_public_key'
- include_role:
name: 'borg'
tasks_from: 'server'
args:
apply:
delegate_to: '{{ client.server }}'
vars:
server:
name: '{{ client.name }}'
pubkey: '{{ borg_public_key.content | b64decode | trim }}'
- name: 'Deploy the jobs script'
template:
src: 'jobs.sh'
dest: '/etc/borg/{{ client.name }}.sh'
owner: 'root'
mode: '0500'
- name: 'Deploy the systemd service and timer'
template:
src: '{{ item.src }}'
dest: '{{ item.dest }}'
owner: 'root'
mode: '0444'
notify: 'systemctl daemon-reload'
loop:
- { src: 'jobs.service', dest: '/etc/systemd/system/borg-job-{{ client.name }}.service' }
- { src: 'jobs.timer', dest: '/etc/systemd/system/borg-job-{{ client.name }}.timer' }
- name: 'Activate job'
service:
name: 'borg-job-{{ client.name }}.timer'
enabled: true
state: 'started'
```
The server.yaml contains:
``` yaml
---
# Inputs:
# server:
# name: string
# pubkey: string
- name: 'Run common tasks'
include_tasks: 'main.yaml'
- name: 'Create borg group on server'
group:
name: 'borg'
system: 'yes'
- name: 'Create borg user on server'
user:
name: 'borg'
group: 'borg'
shell: '/bin/sh'
home: '/srv/borg'
createhome: 'yes'
system: 'yes'
password: '*'
- name: 'Ensure borg directories exist on server'
file:
state: 'directory'
path: '{{ item }}'
owner: 'borg'
mode: '0700'
loop:
- '/srv/borg/.ssh'
- '/srv/borg/{{ server.name }}'
- name: 'Authorize client public key'
lineinfile:
path: '/srv/borg/.ssh/authorized_keys'
line: '{{ line }}{{ server.pubkey }}'
search_string: '{{ line }}'
create: true
owner: 'borg'
group: 'borg'
mode: '0400'
vars:
line: 'command="borg serve --restrict-to-path /srv/borg/{{ server.name }}",restrict '
```
### Handlers
I have a single handler:
``` yaml
---
- name: 'systemctl daemon-reload'
shell:
cmd: 'systemctl daemon-reload'
```
### Templates
The `jobs.sh` script contains:
``` shell
#!/usr/bin/env bash
###############################################################################
# \_o< WARNING : This file is being managed by ansible! >o_/ #
# ~~~~ ~~~~ #
###############################################################################
set -euo pipefail
archiveSuffix=".failed"
# Run borg init if the repo doesn't exist yet
if ! borg list > /dev/null; then
borg init --encryption none
fi
{% for job in client.jobs %}
archiveName="{{ ansible_fqdn }}-{{ client.name }}-{{ job.name }}-$(date +%Y-%m-%dT%H:%M:%S)"
{% if job.pre_command is defined %}
{{ job.pre_command }}
{% endif %}
{% if job.command_to_pipe is defined %}
{{ job.command_to_pipe }} \
| borg create \
--compression auto,zstd \
"::${archiveName}${archiveSuffix}" \
-
{% else %}
borg create \
{% for exclude in job.exclude|default([]) %} --exclude {{ exclude }}{% endfor %} \
--compression auto,zstd \
"::${archiveName}${archiveSuffix}" \
{{ job.paths | join(" ") }}
{% endif %}
{% if job.post_command is defined %}
{{ job.post_command }}
{% endif %}
borg rename "::${archiveName}${archiveSuffix}" "${archiveName}"
borg prune \
--keep-daily=14 --keep-monthly=3 --keep-weekly=4 \
--glob-archives '*-{{ client.name }}-{{ job.name }}-*'
{% endfor %}
borg compact
```
The `jobs.service` systemd unit file contains:
``` ini
###############################################################################
# \_o< WARNING : This file is being managed by ansible! >o_/ #
# ~~~~ ~~~~ #
###############################################################################
[Unit]
Description=BorgBackup job {{ client.name }}
[Service]
Environment="BORG_REPO=ssh://borg@{{ client.server }}/srv/borg/{{ client.name }}"
Environment="BORG_RSH=ssh -i /etc/borg/{{ client.name }}.key -o StrictHostKeyChecking=accept-new"
CPUSchedulingPolicy=idle
ExecStart=/etc/borg/{{ client.name }}.sh
Group=root
IOSchedulingClass=idle
PrivateTmp=true
ProtectSystem=strict
ReadWritePaths=/root/.cache/borg
ReadWritePaths=/root/.config/borg
User=root
```
Finally the `jobs.timer` systemd timer file contains:
``` ini
###############################################################################
# \_o< WARNING : This file is being managed by ansible! >o_/ #
# ~~~~ ~~~~ #
###############################################################################
[Unit]
Description=BorgBackup job {{ client.name }} timer
[Timer]
OnCalendar=daily
Persistent=false
[Install]
WantedBy=timers.target
```
## Invoking the role
The role can be invoked by:
``` yaml
- include_role:
name: 'borg'
tasks_from: 'client'
vars:
client:
jobs:
- name: 'data'
paths:
- '/srv/vaultwarden'
- name: 'postgres'
command_to_pipe: "su - postgres -c '/usr/bin/pg_dump -b -c -C -d vaultwarden'"
name: 'vaultwarden'
server: '{{ vaultwarden.borg }}'
```
## Conclusion
I am happy with this new design! The immediate consequence is that I am archiving my old role since I do not intend to maintain it anymore.