logkeys is a linux keylogger. It is no more advanced than other available linux keyloggers, but is a bit more up to date, actively developed, it doesn't unreliably repeat keys and it should never crash your X. All in all, it just seems to work. It relies on event interface of the Linux input subsystem. Once set, it logs all common character and function keys, while also being fully aware of Shift and AltGr key modifiers. It works with serial as well as USB keyboards.