http://qkpm2ov2rjhjkhfsftskqho77uj5rewd5y44unkf6cb7tdhaxwcvh2id.onion/books/apc/APCUPSD%20User%20Manual.html
But if your normal ID has an environment setup
for using the C compiler, it's simpler to do that than to set up
root to have the correct environment. apcupsd requires gcc and g++ compilers as well as GNU make .
Other compilers or BSD make will not work.