Set up your linux server with the steps provided by BI-Wiki
start your server with headless client configuration (-client -connect=%IP% -port=%port% -name=%nameOfHC% -nosound -noFilePatching)
restart your dedicated game-server after headless client connected and sits in the slot correctly
switch to your terminal of the headless client
observe the messages
("No message from server for N seconds".... final message is: "Connection with the host has been lost")