Messages in this thread | | | Date | 20 Dec 1997 10:58:33 -0000 | From | "Olaf Titz" <> | Subject | Emergency shutdown feature |
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> mike> Or you could plug in elcheapo joystick and run "shutdown -r now" when > mike> both buttons are pressed for more than 5 seconds.
Such a pattern runs the risk of being activated when someone actually _uses_ the joystick for games. :-) But I can imagine some keyboard tricks that are rather unlikely to be triggered by accident.
> I know that gpm can be setup to do this...
and init can react to key combinations too. The problem is that these are user processes, and they won't get a chance when the scheduler is hosed. (Which can happen with such trivial mistakes as a process running SCHED_RR in an endless loop.) An emergency reboot like this has to be in the kernel, called from some interrupt.
I sometimes wanted a simple emergency reboot activated over the network. This would supposedly be rather easy to implement. I'm thinking about the following: a datagram has to be received (via IP is most convenient I think) with a special type which contains e.g. the target host name and current system time in 10 seconds granularity (to allow for clock fuzz) signed with a secret key (MD5 suffices). The feature is activated by writing this key into a /proc/sys entry. The cryptographic setup is to prevent trivial DOS attacks, and this way the feature has to be activated explicitly.
(Coding a "client" for that is left as an exercise :-)
olaf
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