Update README

README.md

@@ -68,6 +68,7 @@ of your `kvm/qemu` virtual machines.
   - [Backup fails with "Cannot store dirty bitmaps in qcow2 v2 files"](#backup-fails-with-cannot-store-dirty-bitmaps-in-qcow2-v2-files)
   - [Backup fails with "unable to execute QEMU command 'transaction': Bitmap already exists"](#backup-fails-with-unable-to-execute-qemu-command-transaction-bitmap-already-exists)
   - [Backup fails with "Error during checkpoint removal: [internal error: bitmap 'XX' not found in backing chain of 'XX']"](#backup-fails-with-error-during-checkpoint-removal-internal-error-bitmap-xx-not-found-in-backing-chain-of-xx)
+  - [Backup fails with "Virtual machine does not support required backup features, please adjust virtual machine configuration."](#backup-fails-with-virtual-machine-does-not-support-required-backup-features-please-adjust-virtual-machine-configuration)
   - [Backup fails with "Timed out during operation: cannot acquire state change lock"](#backup-fails-with-timed-out-during-operation-cannot-acquire-state-change-lock)
   - [Backup fails with "Failed to bind socket to /var/tmp/virtnbdbackup.XX: Permission denied"](#backup-fails-with-failed-to-bind-socket-to-vartmpvirtnbdbackupxx-permission-denied)
   - [High memory usage during backup](#high-memory-usage-during-backup)
@@ -1127,6 +1128,13 @@ You can cleanup this situation by removing the reported checkpoints via:
  virsh checkpoint-delete <domain> --checkpointname <checkpoint_name> --metadata
 ```
 
+## Backup fails with "Virtual machine does not support required backup features, please adjust virtual machine configuration."
+
+The libvirt version you are using does by default not expose the functionality
+required for creating full or incremental backups. You can either use the
+backup mode `copy` or enable the backup features as described
+[here](#libvirt-versions--760-debian-bullseye-ubuntu-20x)
+
 ## Backup fails with "Timed out during operation: cannot acquire state change lock"
 
 If backups fail with error: