Draytek Vigor2820 Series User Manual page 240

Access Rule
Before you click OK, you have to insert a USB disk into the USB interface of the Vigor router.
Otherwise, you cannot save the configuration.
Vigor2820 Series User's Guide
It determines the authority for such profile. Any user, who
uses such profile for accessing into USB disk, must follow the
rule specified here.
File – Check the items (Read, Write and Delete) for such
profile.
Directory –Check the items (List, Create and Remove) for
such profile.
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