File System level backups with LVM snapshots

Introduction

The general idea consists in combining an external tool wich is able to do filesystem level incremental backups ( rsync by means of BackupPC in this document) with the possibility to take snapshots of LVM based storage of virtual machines.

Fundamental constraints in this solution are:

• Do not change fundamentally the configuration of an host under BackuPC
• Preserve easy interactive restore directly on the host.

Basically the target host, when a backup is required via ssh connection, instead of directly executing the rsync command, intercepts it and runs a script ("forced command") which:

1. Prepares backup operations (for instance, saving ACL in case of Windows host)
2. Stops or Suspends services which can do important changes on filesystem.
3. Triggers a snapshot of his own storage on PVE host it is runnng on.
4. Revert machine to normal operating state.
5. Redirects original rsync command towards PVE hosts and the snapshot.
   1. Redirected rsync runs on PVE.
6. When redirected rsync finishes, remove the snapshot.

During interactive restore, instead, rsync process runs directly on the host.