This is a known annoying issue. By default, on r4.3, sys-usb has a minimal-usbvm service enabled. Which prevents it from opening the external USB drive in backup or restore dialog. I personally disagree with that design. But it is my personal opinion.
you have many options to restore your backup:
- Attach the external drive containing your backups to a regular AppVM and then restore from it.
- You could disable the
minimal-usbvmservice ofsys-usb, restart it and then you will be able to restore directly from it. But you should give it a couple hundred megabytes of additional RAM in its settings. - You could mount the drive within
sys-usbterminal in some directory and assureuserhas read access to it. Then you will be able to restore from that directory.
I personally use solution 2