Hyper v install

we want the hyper v maschines image backup on a external usb device that weekle changed. what is the best way for this?

That depends a lot on your sever environment and if you are backing up to vhd/vhdz or raw image files. Could you provide some details?

The user wants to keep external USB backups from his Hyper V machines. (Safe)

what did you mean with more details?

For example if you backup to Linux btrfs the best way to replicate is using btrfs send/receive.