The Magic SysRQ Key on the Keyboard - Chris Titus Tech
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Date: 2022-03-21
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Comments and reviews: 10
David
I use System Request (SysRq) a lot as someone with an IBM i / AS/400 / iSeries background. I won-t get into a full history of its obscurity, but I-ll point out some tidbits of its use:
SysRq used to be its own dedicated key around the IBM PC/AT era, years before it became green text on Model M keyboards, indicating its activation by Alt+Print Screen. It was originally intended to have high priority, much like Control-Alt-Delete does now.
From the perspective of AS/400 terminals, it is activated by pressing Shift+Attn (Attention), which is one of 10 keys to the left of the main keys on a typical 122-key terminal keyboard. On these systems, you can immediately see its use even when the keyboard is in a -locked- state. A status line will appear on the bottom row, where you can often use it to interrupt a process, which is especially handy at times when you-re controlling the master console in dedicated mode.
Some of us have certain key sequences burnt into our brains, like SysRq+1 = launch a secondary session, SysRq+2 = EndRq, SysRq+4 = DSPMSG, SysRq+6 = DSPMSG QSYSOPR, and so on.
As for uses on IBM PC compatibles, the task of SysRq had some obscure uses in DOS applications, but became most known as a means of capturing the active window into the clipboard on Windows 3.0 onward.
So there-s a quick mini-history from the perspective of someone using SysRq often enough on PCs and AS/400s. I-m fascinated to see its uses from the Linux perspective, in that it has some parallels in terms of its high priority over other keys, as it was originally intended.
reply
I use System Request (SysRq) a lot as someone with an IBM i / AS/400 / iSeries background. I won-t get into a full history of its obscurity, but I-ll point out some tidbits of its use:
SysRq used to be its own dedicated key around the IBM PC/AT era, years before it became green text on Model M keyboards, indicating its activation by Alt+Print Screen. It was originally intended to have high priority, much like Control-Alt-Delete does now.
From the perspective of AS/400 terminals, it is activated by pressing Shift+Attn (Attention), which is one of 10 keys to the left of the main keys on a typical 122-key terminal keyboard. On these systems, you can immediately see its use even when the keyboard is in a -locked- state. A status line will appear on the bottom row, where you can often use it to interrupt a process, which is especially handy at times when you-re controlling the master console in dedicated mode.
Some of us have certain key sequences burnt into our brains, like SysRq+1 = launch a secondary session, SysRq+2 = EndRq, SysRq+4 = DSPMSG, SysRq+6 = DSPMSG QSYSOPR, and so on.
As for uses on IBM PC compatibles, the task of SysRq had some obscure uses in DOS applications, but became most known as a means of capturing the active window into the clipboard on Windows 3.0 onward.
So there-s a quick mini-history from the perspective of someone using SysRq often enough on PCs and AS/400s. I-m fascinated to see its uses from the Linux perspective, in that it has some parallels in terms of its high priority over other keys, as it was originally intended.
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Naka
my razer keyboard just froze, and i can't do shit, i thought that my keyboard broke, lockdown right now, and i use ease of access keyboard to click on the on screen keyboard to do everything, it is just so frustrating, can't do shit, an i used that for like 4 four days, and light bulb pop on my head immediatly, maybe some of them settings on my system disabled my keyboard, maybe i dunno, let me try one more, so i press continuosly that sys rq and my keyboard activate and them rgb pops again, sheeeessshh i felt a huge relief, an when i press windows button, them options pop up again. that button is evil, i will never press that again. it made my life miserable, since i have to do everything with them on screen keyboard...
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my razer keyboard just froze, and i can't do shit, i thought that my keyboard broke, lockdown right now, and i use ease of access keyboard to click on the on screen keyboard to do everything, it is just so frustrating, can't do shit, an i used that for like 4 four days, and light bulb pop on my head immediatly, maybe some of them settings on my system disabled my keyboard, maybe i dunno, let me try one more, so i press continuosly that sys rq and my keyboard activate and them rgb pops again, sheeeessshh i felt a huge relief, an when i press windows button, them options pop up again. that button is evil, i will never press that again. it made my life miserable, since i have to do everything with them on screen keyboard...
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roy
When I worked on Mainframes we had a request key. When pressed the system would immediately respond with a prompt and allow you to cancel a run away process and regain control of a bogged down system. Re IPL of a mainframe was never talenoghtly and was always a scheduled event. I never had a mainframe lock up to a point that I was unable to communicate with the system. Unfortunately every machine that's PC based will get locked up amd the only remedy is to cycle power to it. The o/s writers for PCs have no clue as to how a sysyem should perform.
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When I worked on Mainframes we had a request key. When pressed the system would immediately respond with a prompt and allow you to cancel a run away process and regain control of a bogged down system. Re IPL of a mainframe was never talenoghtly and was always a scheduled event. I never had a mainframe lock up to a point that I was unable to communicate with the system. Unfortunately every machine that's PC based will get locked up amd the only remedy is to cycle power to it. The o/s writers for PCs have no clue as to how a sysyem should perform.
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Shimi
I use it at least for 10 years. It's amazing how i remember and do it automatically, this burn in head.
Use it anytime if system stuck, if not all-least the B, don't force shutdown key - most of time it's kill power for HDD and someday it really kill them (this worse twice for SSD, it's like memory stick, no power - data Poof away!)... do Only if nothing works.
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I use it at least for 10 years. It's amazing how i remember and do it automatically, this burn in head.
Use it anytime if system stuck, if not all-least the B, don't force shutdown key - most of time it's kill power for HDD and someday it really kill them (this worse twice for SSD, it's like memory stick, no power - data Poof away!)... do Only if nothing works.
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ghos282
FATALLY FLAWED ASSUMPTION That the Keyboard will even be recognized when the Linux OS gets frozen up, Typically by something either Facebook or Youtube has HACKED!! When this happens to me, and believe me IT DOES! ..They also manage (Intentionally) to DISABLE KEYBOARD RECOGNITION. So REISUB is a MOOT POINT as it CANNOT BE ACCESSED.
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FATALLY FLAWED ASSUMPTION That the Keyboard will even be recognized when the Linux OS gets frozen up, Typically by something either Facebook or Youtube has HACKED!! When this happens to me, and believe me IT DOES! ..They also manage (Intentionally) to DISABLE KEYBOARD RECOGNITION. So REISUB is a MOOT POINT as it CANNOT BE ACCESSED.
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SysGhost
For those who are unable to -su- due to the root password being scrambled and/or disabled for direct login (which is the way it's supposed to be), use the tee command with a pipe.
Example:
echo -1- - sudo tee /proc/sys/kernel/sysrq
echo -kernel.sysrq = 1- - sudo tee -a /etc/sysctl.d/99-sysctl.conf
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For those who are unable to -su- due to the root password being scrambled and/or disabled for direct login (which is the way it's supposed to be), use the tee command with a pipe.
Example:
echo -1- - sudo tee /proc/sys/kernel/sysrq
echo -kernel.sysrq = 1- - sudo tee -a /etc/sysctl.d/99-sysctl.conf
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Susan
Very useful info thanks for sharing, I would be interested in what you know about init! seems to me this would make a worthwhile video, what it means in Linux and how it affects the Linux system, how to correct errors from init, would all be really helpful.
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Very useful info thanks for sharing, I would be interested in what you know about init! seems to me this would make a worthwhile video, what it means in Linux and how it affects the Linux system, how to correct errors from init, would all be really helpful.
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Feynman
Okay you have to set sysrq to 1 but what are you changing exactly? What did your original number of 16 actually set on the system, are you disabling other functionality to enable this key combination?
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Okay you have to set sysrq to 1 but what are you changing exactly? What did your original number of 16 actually set on the system, are you disabling other functionality to enable this key combination?
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Hoefkens
also but you probably know already , but you can use !! (not -- ) to execute the last entered command again in the console comes in handy when you forgot sudo in front , just enter $sudo !!
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also but you probably know already , but you can use !! (not -- ) to execute the last entered command again in the console comes in handy when you forgot sudo in front , just enter $sudo !!
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Impersonator
With systemd, you can also attempt to recover your computer by entering the RAW keyboard input mode and initiating a reboot sequence with the CTRL+ALT+DELETE key combination.
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With systemd, you can also attempt to recover your computer by entering the RAW keyboard input mode and initiating a reboot sequence with the CTRL+ALT+DELETE key combination.
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