add borg ansible role continued blog article
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content/blog/ansible/borg-ansible-role-2.md
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content/blog/ansible/borg-ansible-role-2.md
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---
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title: 'Borg ansible role (continued)'
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description: 'The ansible role I rewrote to manage my borg backups'
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date: '2024-10-07'
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tags:
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- ansible
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- backups
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- borg
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---
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## Introduction
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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.
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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.
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## Borg repositories changes
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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.
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The main advantages are:
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- one private ssh key per job
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- no more data expiration when a job stops running on a job for a time
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- 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.
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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.
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## The new role
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### Tasks
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The main.yaml contains:
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``` yaml
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---
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- name: 'Install borg'
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package:
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name:
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- 'borgbackup'
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# This use attribute is a work around for https://github.com/ansible/ansible/issues/82598
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# Invoking the package module without this fails in a delegate_to context
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use: '{{ ansible_facts["pkg_mgr"] }}'
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```
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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.
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The meat of the role is in the client.yaml:
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``` yaml
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---
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# Inputs:
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# client:
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# name: string
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# jobs: list(job)
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# server: string
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# With:
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# job:
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# command_to_pipe: optional(string)
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# exclude: optional(list(string))
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# name: string
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# paths: optional(list(string))
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# post_command: optional(string)
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# pre_command: optional(string)
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- name: 'Ensure borg directories exists on server'
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file:
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state: 'directory'
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path: '{{ item }}'
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owner: 'root'
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mode: '0700'
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loop:
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- '/etc/borg'
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- '/root/.cache/borg'
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- '/root/.config/borg'
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- name: 'Generate openssh key pair'
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openssh_keypair:
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path: '/etc/borg/{{ client.name }}.key'
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type: 'ed25519'
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owner: 'root'
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mode: '0400'
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- name: 'Read the public key'
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ansible.builtin.slurp:
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src: '/etc/borg/{{ client.name }}.key.pub'
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register: 'borg_public_key'
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- include_role:
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name: 'borg'
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tasks_from: 'server'
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args:
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apply:
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delegate_to: '{{ client.server }}'
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vars:
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server:
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name: '{{ client.name }}'
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pubkey: '{{ borg_public_key.content | b64decode | trim }}'
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- name: 'Deploy the jobs script'
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template:
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src: 'jobs.sh'
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dest: '/etc/borg/{{ client.name }}.sh'
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owner: 'root'
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mode: '0500'
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- name: 'Deploy the systemd service and timer'
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template:
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src: '{{ item.src }}'
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dest: '{{ item.dest }}'
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owner: 'root'
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mode: '0444'
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notify: 'systemctl daemon-reload'
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loop:
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- { src: 'jobs.service', dest: '/etc/systemd/system/borg-job-{{ client.name }}.service' }
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- { src: 'jobs.timer', dest: '/etc/systemd/system/borg-job-{{ client.name }}.timer' }
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- name: 'Activate job'
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service:
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name: 'borg-job-{{ client.name }}.timer'
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enabled: true
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state: 'started'
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```
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The server.yaml contains:
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``` yaml
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---
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# Inputs:
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# server:
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# name: string
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# pubkey: string
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- name: 'Run common tasks'
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include_tasks: 'main.yaml'
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- name: 'Create borg group on server'
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group:
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name: 'borg'
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system: 'yes'
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- name: 'Create borg user on server'
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user:
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name: 'borg'
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group: 'borg'
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shell: '/bin/sh'
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home: '/srv/borg'
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createhome: 'yes'
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system: 'yes'
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password: '*'
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- name: 'Ensure borg directories exist on server'
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file:
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state: 'directory'
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path: '{{ item }}'
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owner: 'borg'
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mode: '0700'
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loop:
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- '/srv/borg/.ssh'
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- '/srv/borg/{{ server.name }}'
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- name: 'Authorize client public key'
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lineinfile:
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path: '/srv/borg/.ssh/authorized_keys'
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line: '{{ line }}{{ server.pubkey }}'
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search_string: '{{ line }}'
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create: true
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owner: 'borg'
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group: 'borg'
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mode: '0400'
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vars:
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line: 'command="borg serve --restrict-to-path /srv/borg/{{ server.name }}",restrict '
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```
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### Handlers
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I have a single handler:
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``` yaml
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---
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- name: 'systemctl daemon-reload'
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shell:
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cmd: 'systemctl daemon-reload'
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```
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### Templates
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The `jobs.sh` script contains:
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``` shell
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#!/usr/bin/env bash
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###############################################################################
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# \_o< WARNING : This file is being managed by ansible! >o_/ #
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# ~~~~ ~~~~ #
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###############################################################################
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set -euo pipefail
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archiveSuffix=".failed"
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# Run borg init if the repo doesn't exist yet
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if ! borg list > /dev/null; then
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borg init --encryption none
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fi
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{% for job in client.jobs %}
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archiveName="{{ ansible_fqdn }}-{{ client.name }}-{{ job.name }}-$(date +%Y-%m-%dT%H:%M:%S)"
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{% if job.pre_command is defined %}
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{{ job.pre_command }}
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{% endif %}
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{% if job.command_to_pipe is defined %}
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{{ job.command_to_pipe }} \
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| borg create \
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--compression auto,zstd \
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"::${archiveName}${archiveSuffix}" \
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-
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{% else %}
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borg create \
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{% for exclude in job.exclude|default([]) %} --exclude {{ exclude }}{% endfor %} \
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--compression auto,zstd \
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"::${archiveName}${archiveSuffix}" \
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{{ job.paths | join(" ") }}
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{% endif %}
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{% if job.post_command is defined %}
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{{ job.post_command }}
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{% endif %}
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borg rename "::${archiveName}${archiveSuffix}" "${archiveName}"
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borg prune \
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--keep-daily=14 --keep-monthly=3 --keep-weekly=4 \
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--glob-archives '*-{{ client.name }}-{{ job.name }}-*'
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{% endfor %}
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borg compact
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```
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The `jobs.service` systemd unit file contains:
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``` ini
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###############################################################################
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# \_o< WARNING : This file is being managed by ansible! >o_/ #
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# ~~~~ ~~~~ #
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###############################################################################
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[Unit]
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Description=BorgBackup job {{ client.name }}
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[Service]
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Environment="BORG_REPO=ssh://borg@{{ client.server }}/srv/borg/{{ client.name }}"
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Environment="BORG_RSH=ssh -i /etc/borg/{{ client.name }}.key -o StrictHostKeyChecking=accept-new"
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CPUSchedulingPolicy=idle
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ExecStart=/etc/borg/{{ client.name }}.sh
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Group=root
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IOSchedulingClass=idle
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PrivateTmp=true
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ProtectSystem=strict
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ReadWritePaths=/root/.cache/borg
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ReadWritePaths=/root/.config/borg
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User=root
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```
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Finally the `jobs.timer` systemd timer file contains:
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``` ini
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###############################################################################
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# \_o< WARNING : This file is being managed by ansible! >o_/ #
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# ~~~~ ~~~~ #
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###############################################################################
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[Unit]
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Description=BorgBackup job {{ client.name }} timer
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[Timer]
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OnCalendar=daily
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Persistent=false
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[Install]
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WantedBy=timers.target
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```
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## Invoking the role
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The role can be invoked by:
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``` yaml
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- include_role:
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name: 'borg'
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tasks_from: 'client'
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vars:
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client:
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jobs:
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- name: 'data'
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paths:
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- '/srv/vaultwarden'
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- name: 'postgres'
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command_to_pipe: "su - postgres -c '/usr/bin/pg_dump -b -c -C -d vaultwarden'"
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name: 'vaultwarden'
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server: '{{ vaultwarden.borg }}'
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```
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## Conclusion
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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.
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