pptp-linux is based on pppd, so invocation is very similar:

% pptp hostname [ppp-options]

So, for example, I invoke pptp with:

pptp my.pptp.host debug name cananian remotename ntdialup 172.18.0.2:172.18.0.3
route add -net 172.18.0.0 netmask 255.255.0.0 gw 172.18.0.3

You will see three pptp-related processes in your process list: a call
manager, a GRE/PPP en/decapsulator, and pppd.  To shut down the pptp
connection, kill the pppd process.

NOTE THAT PPTP MUST BE RUN AS ROOT.

Most trouble with pptp will probably be due to incorrect pppd
configuration. Be sure you thoroughly understand MS-CHAP support in
pppd.  Use the 'debug' option to pppd to log connection information;
this will help you trouble-shoot the pppd side of pptp.
