/sector_chmod 12 2 2 + peace
RETURN: [SERVER, [ADMIN COMMAND] [SUCCESS] set peace on (12, 2, 2) to 'true', 0]
RETURN: [SERVER, END; Admin command execution ended, 0]
Pirates don't invade.
...
Restart server, pirates invade again.
12 2 2, and all immediately-touching sectors, are also set to + peace/protected/noenter/noexit