http://qkpm2ov2rjhjkhfsftskqho77uj5rewd5y44unkf6cb7tdhaxwcvh2id.onion/books/apc/APCUPSD%20User%20Manual.html
If your operating system is older, or if you have an old-fashioned
serial-line UPS, you'll have to read about serial installation (see Installation: Serial-Line UPSes ). If you need more
details about administration for unusual situations (such as a
master/slave or multi-UPS setup) you'll need to read the sections on
those topics as well. Finally,
there are a number of technical reference sections which
gives full details on things like configuration file directives and
event-logging...