Messages in this thread | | | Date | Sat, 20 Dec 1997 14:32:37 +0100 | From | Pavel Machek <> | Subject | Re: Emergency shutdown feature - already solved, see magic sysrq |
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Hi!
> 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.
This is all done, look at magic sysrq (standart feature in 2.1.X kernels).
> 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.
Hmm. I was also thinking on making magic sysrq work over the network. Trouble is, how to do it securely. This looks nearly like solution!
(mj: any comments?)
Pavel
-- I'm really pavel@atrey.karlin.mff.cuni.cz. Pavel Look at http://atrey.karlin.mff.cuni.cz/~pavel/ ;-).
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