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Ansible Role: BorgBackup

An Ansible role that installs and configures a systemd service for BorgBackup on a client and (delegated) server. This allows you to very easily add backups to your hosts.

The documentation assumes basic knowledge about BorgBackup. You can get up to speed with Borg by reading their excellent documentation on https://borgbackup.readthedocs.io.

How it works

sequenceDiagram
participant Ansible
participant borg-client
participant borg-server

Ansible->>borg-server: Install dependencies
Ansible->>borg-client: Install dependencies
Ansible->>borg-server: Setup Repository
Ansible->>borg-client: Setup Repository
Ansible->>borg-client: Setup backup job
borg-client->>Ansible: Store decryption keys
borg-client-->borg-server: Do Backup
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Installation

via ansible-galaxy

ansible-galaxy role install kliwniloc.borgbackup
# requirements.yml
- src: kliwniloc.borgbackup

via git

ansible-galaxy role install git+https://github.com/kliwniloc/ansible-role-borgbackup.git,master
# requirements.yml
- src: https://github.com/kliwniloc/ansible-role-borgbackup
  version: master
  name: kliwniloc.borgbackup

Role Variables

For more details, see: defaults/main.yml

You need to specify your Borg hostname (as defined in your Ansible inventory) as well as the public SSH key from that Borg SSH server. You can get this key by scanning the Borg server host like this: ssh-keyscan -t rsa borg.example.org and removing the hostname, so the output looks like this: ssh-rsa AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA....

If the Ansible hostname is not reachable from the client host, you must set borg_server_host_url to a host that is reachable from the Borg clients. It will default to borg_server_host.

  • borg_server_host is used by Ansible to delegate tasks to the Borg server
  • borg_server_host_url is used by the client to connect to the Borg server
borg_server_host: "" # Required
borg_server_host_ssh_key: "" # Required
borg_server_host_url: {{ borg_server_host }} # Optional

The role creates a user for the Borg repositories on the Borg server. You can specify the location of the home directory with borg_server_user_home, which will also be the location for the backups.

borg_server_user_home: /opt/borg

For the backup itself, there are a few Borg parameters you can configure. Not all options that Borg offers are available in the Ansible role yet. For more configuration options, see https://borgbackup.readthedocs.io.

borg_repo_name configures the name of the repository as it is created on the Borg server in the borg_server_user_home directory. By default, we use the inventory hostname, which is fine if you don't use multiple Borg repositories on the same client and server hosts. The individual backup names can be customized in the borg_backup_name_format variable. You can use placeholders such as {hostname} for the backups, see: https://borgbackup.readthedocs.io/en/stable/usage/help.html#borg-help-placeholders.

borg_mode_append_only restricts the deletion of the backups from the client. This can increase security but comes at the cost of not being able to clean up old backups from the client.

borg_repo_name: "{{ inventory_hostname }}"
borg_backup_name_format: "{hostname}-{now:%Y-%m-%dT%H:%M:%S}"
borg_mode_append_only: false # Server side append only config

We use zstd compression by default, but you can change it to any of the supported modes see: https://borgbackup.readthedocs.io/en/stable/usage/help.html#borg-help-compression.

You can configure a passphrase for the encryption keys in borg_passphraseof your Borg backups, but it is not used by default.

borg_included_dirs and borg_excluded_dirs finally picks what directories will be backed up by Borg.

borg_compression: zstd # -C argument
borg_passphrase: "" # Env variable
borg_included_dirs: [] # Positional arguments
borg_excluded_dirs: [] # --exclude arguments

To decrypt your backups without the client, we store the decryption keys in a YAML file in your Ansible repository. You require the decryption keys as well as access to the repository files on the Borg server to access the backups. If you wish to add another layer of security for these decryption keys, consider using git encryption tools like https://github.com/AGWA/git-crypt or storing the keys in a secure location outside of git.

borg_decryption_keys_yaml_path: "{{ inventory_dir }}/decryption_keys.yml"

The scheduling of the backups is done via systemd. For this purpose a systemd service and a corresponding timer are created. Additionally, we create backup scripts for use in the systemd service and for the ability to easily trigger manual backups.

To support multiple backups (with different schedules), we have the borg_backup_argument which defaults to {{ borg_server_host_url }} and should be unique per backup target. The names of the systemd service and timer are: {{ borg_backup_timer_name }}{{ borg_backup_argument }}.service and {{ borg_backup_timer_name }}{{ borg_backup_argument }}.timer.

For the backup scripts we add {{ borg_backup_script_location }} for creating a backup on all specified targets and {{ borg_backup_script_location }}{{ borg_backup_argument }} for backing up to each target.

To configure the backup schedule, we offer borg_systemd_oncalendar and borg_systemd_accuracysec, which map to the corresponding systemd options, see man-page systemd.timer(5).

borg_backup_script_location: /usr/local/bin/run_borg_backup
borg_backup_timer_name: borg_backup
borg_backup_service_name: borg_backup
borg_backup_argument: '{{ borg_server_host_url }}'
borg_systemd_oncalendar: '*-*-* 02:00:00'
borg_systemd_accuracysec: 60min

Example Playbooks

Simple Playbook

- name: >
    Add Borg backup to the borg-client and save the
    decryption keys alongside the playbook
  hosts: borg-client
  roles:
    - role: kliwniloc.borgbackup
      borg_server_host: borg-server
      borg_server_host_ssh_key: ssh-rsa AAAAAAAA...
      borg_decryption_keys_yaml_path: "{{ playbook_dir }}/decryption_keys.yml"
      borg_included_dirs:
        - /home
        - /opt/project

Multiple Backup servers

- name: >
    Add Borg backup with multiple borg servers to the borg-client and
    save the decryption keys alongside the playbook
  hosts: borg-client
  vars:
    borg_included_dirs:
      - /home
      - /opt/project
  roles:
    - role: kliwniloc.borgbackup
      borg_server_host: borg-server1
      borg_server_host_ssh_key: ssh-rsa AAAAAAAA...
    - role: kliwniloc.borgbackup
      borg_server_host: borg-server2
      borg_server_host_ssh_key: ssh-rsa BBBBBBBB...

Dependencies

None.

License

MIT