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Only with a UPS

Only with a UPS

Posted Sep 11, 2009 5:28 UTC (Fri) by magnus (subscriber, #34778)
In reply to: Only with a UPS by ncm
Parent article: POSIX v. reality: A position on O_PONIES

In my experience, system hangs are much more common than power outages for desktop systems.

In the past I've had to reboot due to X server hangs (probably problems in the display driver), oopses due to unstable hardware (memory mainly) and sometimes soft hangs like losing connection to an NIS or NFS server or getting PAM misconfigured and not having a prompt to work from.

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Only with a UPS

Posted Sep 19, 2009 20:30 UTC (Sat) by efexis (guest, #26355) [Link]

Alt+Printscreen+U. Always press it before reboot, if the kernel's not oopsed, can save you data :-)

Only with a UPS

Posted Sep 20, 2009 7:51 UTC (Sun) by Cato (subscriber, #7643) [Link]

There are some other handy Magic SysRq (i.e. Alt-PrintScreen) keystrokes as well:

Only with a UPS

Posted Sep 21, 2009 7:20 UTC (Mon) by efexis (guest, #26355) [Link]

Although I wouldn't recommend using S(ync) as the third option for rebooting the system, after terminating processes etc. If the system's becoming unstable, syncing the drives is the very first thing I'd want to do. I prefer the order S-E-I-U-B. AFAIA, an S before U is redundant as buffers are written out as part of the remount-ro process, so a seperate sync() isn't needed (if anyone knows otherwise please correct me).

But of all those, the U is the most important, as if it succeeds it will protect your filesystem. You may end up with some left over temp files as tasks that didn't receive the terminate request signal didn't clean up after themselves, but this is usually not too great a cost.


Only with a UPS

Posted Sep 22, 2009 6:13 UTC (Tue) by Cato (subscriber, #7643) [Link]

Yes, personally I prefer the mnemonic Raising Skinny Elephants Is Utterly Boring.

Only with a UPS

Posted Sep 22, 2009 9:28 UTC (Tue) by efexis (guest, #26355) [Link]

Does the R do much? If you're rebooting/etc anyway... if the kernel's able to trap the Alt+SysRq+R, then it can trap the S/E/I/U/B keys too? Or is there another reason for it?

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