Keep a file or directory in sync with another ansible-managed host

This role is intended to copy SSL-certificates generated on another host to the current host using scp or rsync (optional) and keep it in sync by adding a cronjob. It is not limited to SSL certificates and may well be used to copy any other file or directory.

These variables must be set in order to use this role

sync_source_host_ansible: The other host from which the file or directory should be copied. This name must be known by ansible.
sync_source_host: Source IP address or host name under which the other host in reachable from the currently processed host.
sync_source: Full path to the file or directory to be synced.
sync_target_dir: Target directory under which the basename of sync_source will be created.

Optional variables

sync_minutes: How long to wait between syncs. Defaults to 15 (every 15 minutes the sync task is executed).
sync: Defaults to scp. If set to rsync rsync will be installed on target and source and is used to sync files.
additional_commands: Command line to be executed after every sync.

What this role does

Create a dedicated SSH key for this job.
Add this key to the root user's authorized_keys file on sync_source_host_ansible, making sure that you are only allowed to read sync_source when using this key.
Run the copy job initially.
Add a cronjob that runs the copy job once every hour.

Example usage

- hosts: mail
  vars:
    sync_source_host_ansible: my_other_host
    sync_source_host: 192.168.1.42
    sync_source: /etc/certs/example.com
    sync_target_dir: /srv/certs
    sync_minutes: 10
  roles:
    - { role: rompe.sync_dir_from_other_host, tags: "sync_dir" }

After running this, /srv/certs/example.com will be in place and kept current every 10 minutes.

Restrictions and Solutions

Using scp is quite simple and works well with a small number of files, as all files are copied on every run. It has no prerequisite. To better scale with the number of files to transfer rsync can be used as option. However, rsync needs to be installed on both, source and target hosts. To use rsync, just set the variable sync to rsync.

License

Licensed under the MIT License. See the LICENSE file for details.

Author information

Created by Ulf Rompe in 2018. Changed to rsync by Jens Gecius in 2020.

rompe/ansible-sync-dir-from-other-host