(1) Please see this post to start ppup1090 by systemd instead of rc.local
(2) Please see this post for workaround for a bug in ppup1090 which causes it to go crazy and use 100% cpu when dump1090-fa restarts (ppup1090 cannot handle properly disconnection from dump1090-fa)
Solution is to add following line under [unit] in ppup1090.service file:
PartOf=dump1090-fa.service