Secure screenlocking with X and tty login

Question

I choose not to run a login manager on my systems, instead opting for a tty login and then invoking xinit manually (slightly long story, it makes my life a lot easier to have a bunch of environment tweaks that my login shell sets up and has the rest inherit), but this leaves me with a security issue if someone else comes upon my PC, because even if I've locked my X session they can switch to a tty and kill my X session, dropping back to a shell.

I can either

1. Start running xinit; logout (which still has a race condition issue, if they get another Ctrl+C in before logout is invoked it'll give a shell)
2. Try to disable the tty switching keys in X
3. Wrap xinit in something to catch and ignore the signal from the Ctrl+C

Or some better solution that I've not considered.

Answer 1

• exec xinit will replace your shell process with xinit; it remains killable, but if it is later killed, you get dropped to the login screen.

• setsid xinit; logout or (xinit &); logout will start xinit in background and then end the tty session immediately. This is even better – X11 cannot be ^C'ed anymore.

  (Such combinations as exec setsid xinit may work, I haven't tried.)

_{FWIW, some login managers do read "environment tweaks" from the standard ~/.profile; I know GDM does.}