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.
   • Redirected rsync runs on PVE.
6. Triggers snapshot snapshot removal on PVE.

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