last time i got a headcrash by turning power off was on my old 8086 - there was even a dos command to park the head - but that was more than 20 years ago, hardware has changed quite a bit since then :-) n. Am Dienstag, 25. Juli 2006 18:06 schrieb Shane Geiger: > DON'T DO SHUTDOWN OR HALT UNLESS YOU HAVE TO--AND YOU RARELY DO. :-) > > This makes little sense on a Live CD, and it takes too much time. You > could power off the machine, but what happens if you forget to unmount > something? > > The safe way to quickly shut down a live CD-booted machine or one > running from the hard drive is to use the magic sysrq functionality (if > it's in your kernel). > > On a laptop, I often use alt-sysrq (since I don't have any network > services running from it or any databases). You can also use alt-sysrq > on a machine that has frozen--it's a much safer alternative to cutting > the power to the machine. > > ------------------------- > source: > http://linuxreviews.org/news/2004-06-11_kernel_crash/index.html#toc1 > > If you enabled Magic SysRq (CONFIG_MAGIC_SYSRQ=y, found in make > menuconfig at Kernel hacking -> Kernel debugging -> Magic SysRq key) in > your kernel you can cleanly reboot if evil freezes your system with the > following keyboard combination: > > 1. Alt-SysRq-R (keyboard in raw mode) > 2. Alt-SysRq-S (save unsaved data to disk) > 3. Alt-SysRq-E (send termination signal) > 4. Alt-SysRq-I (send kill signal) > 5. Alt-SysRq-U (remount all mounted file systems) > -- SHANE: IS THAT REMOUNTING OR UNMOUNTING??? I THINK > THAT'S AN ERROR. > 6. Alt-SysRq-B (reboots the system) > > ------------------------- > source: http://aplawrence.com/Words2005/2005_04_13.html > > Alt+SysRq+e - try to nicely kill processes > (wait a little bit here) > Alt+SysRq+i - no more mister nice guy > Alt+SysRq+s - sync the disk > Alt+SysRq+u - unmount disks > (wait a bit here, too) > Alt+SysRq+b - reboot > > It's better to Sync AFTER killing your processes, just before unmounting > the filesystems, so a safter sequence would be E-I-S-U-B. And you can > even have fun with the acronym; "Everything Is Super, Uncle Ben!" > > > If you find that holding three keys is difficult, you do have some other > choices. You can trigger it manually: > > echo t > /proc/sysrq-trigger > > Or, you can make the Alt-SysRq "sticky" by: > > echo 1 > sysrq-sticky > > With that done, you can hold Alt-SysRq, release it, and then leisurely > press "t" or whatever key you wanted. > > You could also change the SysRq itself in /proc/sys/kernel/sysrq-key > (it's normally 84 - Alt-SysRq for Intel). > > ------------------------- > > If you are trying to do this sort of thing from a script, you can do > something like this: > > #!/bin/bash > sudo su -c 'echo e > /proc/sysrq-trigger; sleep 3; echo i > > /proc/sysrq-trigger; echo s > /proc/sysrq-trigger; echo u > > /proc/sysrq-trigger; sleep 3; echo b > /proc/sysrq-trigger' > > # Note: I'm not sure why the sleep statements are needed. But, rest > assured, this gets the job done. > > Stephen Samuel wrote: > > Depends on whether or not you have swap. If you do, there is a SMALL > > possibility that you could power down during a write to the swap > > artition and that you would get a spurious write that could trash the > > partition data -- or even real data. > > > > I usually use ''poweroff -f' It takes all of about 3-10 seconds with > > Knoppix 5.0.1, and ensures that there > > are no spurious writes. > > > > Tim Ross wrote: > >> If you're running the Live CD and don't have any external devices > >> mounted, can you power the machine down with the on/off button rather > >> than do a clean shutdown without hurting anything? > >> > >> Since we're dealing with a RAM disk, I'd think nothing would get > >> "hurt" by killing the power (and it would be faster)... > > -- > Shane Geiger > IT Director > National Council on Economic Education > sgeiger@ncee.net | 402-438-8958 | http://www.ncee.net > > Leading the Campaign for Economic and Financial Literacy
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