Re: Forcing an immediate reboot

From: Petr Vandrovec
Date: Sat Oct 15 2005 - 19:11:17 EST

Anton Altaparmakov wrote:
On Sat, 15 Oct 2005, Coywolf Qi Hunt wrote:

On 10/15/05, Anton Altaparmakov <aia21@xxxxxxxxx> wrote:

echo s > /proc/sysrq-trigger
echo u > /proc/sysre-trigger
echo s > /proc/sysrq-trigger

What the purpose of the second sync?

Allows any i/o initiated between the first sync and the remount r/o to complete. Remember that r/o mounting doesn't stop i/o. It only stops you from writing to the fs at the vfs layer. Once a write/modification has entered the fs driver it will get written no matter what, unless the "reboot" sysrq is triggered in which case the kernel just reboots immediately.

Maybe it is just paranoia on my part but I have gotten used to hitting Alt+PrtScr+S, +U, +S, +B so I do it automatically.

Second sync is a must, otherwise remounting read-only is not written to the filesystem (at least in my case) so no fsck is saved. But you can save first sync (before remount), and then you get nice sequence which even admins comming from Windows can remember - they have to use USB to safely reboot their Linux systems ;-) (alt-sysrq-U, S, B)

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