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Questions tagged [magic-sysrq]

The "magic sysrq" key sequence is a feature of the Linux kernel that, when enabled, provides debugging and disaster recovery features on the system console and serial console.

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sysrq won't reboot with a keystroke, but will with echo “b” > /proc/sysrq-trigger

CentOS 6.2, 2.6.32-220.el6.x86_64 laptop. SysRQ is enabled for keyboard input, as is witnessed by: $ cat /proc/sys/kernel/sysrq 1 Common Magic SysRQ Keys are working such as alt-sysrq-h. However, ...
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What is raw keyboard mode?

In the magic sysrq key combinations, there is the combination alt+sysrq+r which, according to wikipedia, does the following: Switch the keyboard from raw mode, the mode used by programs such as ...
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Alt+SysRq+T not working / Where do SysRq commands print to?

My REISUB commands, and K, work flawlesly, but with T (it should print info about tasks), it prints nothing. H also doesn't work. Alt+SysRQ+H Alt+SysRQ+T I tried in all tty's (even F10, which doesn'...
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Why is Magic SysRq not enabled by default on some systems? Is there a risk?

While troubleshooting a Oracle Linux 6.3 server (RHEL Derivative) I tried to use some of the Magic SysRq Key commands for the first time. No such luck so I had to hard reboot. When it came back up I ...
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What numeric key codes do I need to send for the magic sysrq functionality in a VNC session?

I have access to the system console of a KVM guest through VNC. What key codes do I need to send for the magic sysrq sequence (Ctrl+Alt+"REISUB") in Linux? Edit: In Linux under qemu, running showkey ...
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Under what circumstance could switching tty's and entering commands freeze?

I noticed, that when booted from a live disc, and the RAM is filled up nearly, the live DVD starts being accessed far more often (probably due to exhausted and squished block cache) and switching tty'...
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How to ensure SysRq is always enabled regardless of the kernel.sysrq setting?

Some Linux distributions have kernel.sysrq=16 which means only Sysrq+s (sync) is allowed. As an example: Fedora (25 and 28) has it set as such in /usr/lib/sysctl.d/50-default.conf I had to create a ...
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Kernel Crash/ Cpu error?

First I will describe my system and then my problem: I have an Assus F555L laptop with an i3 and Intel Integrated Graphics. It is running Linux Mint 17.3 and Windows 10 dual booted. I do not have ...
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How to stop a SysRq command?

I used SysRq+J (thaw), now I am being flooded with printk messages: emergency thaw on sr0. It will never stop. I do not wish to wait, until a SysRq command ends while blocking the terminal all the ...