+.B INDEXDB
+The name of a SQLite database initialized by
+.BR update-bkp-index (8)
+in which an index is maintained of which dumps are on which backup
+volumes. If the file doesn't exist, then no index is maintained. The
+default is
+.IB localstatedir /lib/bkp/index.db
+where
+.I localstatedir
+is the state directory configured at build time.
+.TP