supports snapshots. Using the `backup=no` mount point option individual volumes
can be excluded from the backup (and thus this requirement).
-NOTE: bind and device mount points are skipped during backup operations, like
-volume mount points with the backup option disabled.
-
+// see PVE::VZDump::LXC::prepare()
+NOTE: By default additional mount points besides the RootDisk mount point are
+not included in backups. For volume mount points you can set the *Backup* option
+to include the mount point in the backup. Device and bind mounts are never
+backed up as their content is managed outside the {pve} storage library.
Backup File Names
-----------------