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Does Your PC Really Need a SysRq Button Anymore?
An anonymous reader writes "Ever wondered what the SysRq key on your keyboard does? Lenovo has decided it's so rarely used that it has started removing the key from some new Thinkpad Edge laptops. We already know that Lenovo are something of the fastidious scientists when it comes to keyboard design. Last time they fiddled with the age-old key layout, it was after painstaking research to count exactly how many times users press the Delete and Escape keys. Now it seems another relic of computer keyboards is starting to disappear."
Ever wondered what the SysRq key on your keyboard does?
Introduced by IBM with the PC/AT, it was intended to be available as a special key to directly invoke low-level operating system functions with no possibility of conflicting with any existing software.
In Linux, the kernel can be configured to provide functions for system debugging and crash recovery.[4] This use is known as the "Magic SysRq key".
Microsoft has used SysRq for various OS- and application-level debuggers. In the CodeView debugger, it was sometimes used to break into the debugging during program execution.[5] For the Windows NT remote kernel debugger, it can be used to force the system into the debugger.[6]
So it's a handy debugger key for those who need one, functioning in the same key as print screen, but you need to hold alt key. What's the harm having it there, since it already is? It's not like it's an extra button on your keyboard.
On my laptop, I use it to toggle VMs. It's perfect because on my machine, it does absolutely nothing. Double scroll lock is the next best bet for me, but my keyboard requires me to press the Fn key simultaneously.
Is Lenovo leaving any "useless" keys? Some of us actually NEED keys that are otherwise never used and the OSes recognize by default.
"You can have my SysRq key when you pry it from my cold dead ThinkPad!"
That is the Print Screen key. Don't ever remove that key from the keyboard! I don't care that the word "SysRq" is written below "Print Screen" on that key. Feel free to remove that "SysRq" word from there, but do NOT remove the handy print screen key! Thanks.
Yep... just confirmed that it also works even if Linux isnt frozen...
that the user is pressing the SysRq key.
In fact, to *urgently* tell the OS that the SysRq. It's not supposed to be buffered or anything, it supposed to grab the OS by the collar and scream "THE USER JUST PRESSED THE DAMMNED SYSRQ KEY!!!!" at it.
But what is that supposed to mean?
It doesn't mean anything.
That's the whole point.
When they were designing the keyboard, they thought of all the things that you might want a keyboard to say ("STOP SCROLLING", "Show me that last page", "Get me the hell out of this input mode"). And after they'd mandated keys for everything anybody could think of, they had a stroke of genius. They mandated a key that did nothing anybody wanted to do.
Why is that a stroke of genius?
It is something rare in engineering, which thrives on bravado and feverishly inflated self-confidence. It is an admission of the limitation of human foresight, an acknowledgement that there are more things under Heaven and Earth than are dreamt of in our philosophies; a semiotic *memento mori*.
This key is mandated to mean nothing, therefore it can mean anything, or indeed, everything.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
I actually use Alt - SysRq - R + E + I + S + U + B:
* R: Switch the keyboard from raw mode to XLATE mode
* E: Send the SIGTERM signal to all processes except init
* I: Send the SIGKILL signal to all processes except init
* S: Sync all mounted filesystems
* U: Remount all mounted filesystems in read-only mode
* B: Immediately reboot the system, without unmounting partitions or syncing
You don't need to hold the REISUB keys, so you can use your left hand to hold Alt, your right one to hold SysRq and use the free fingers to type REISUB.
You don't. You hold down alt and sysrq, but the other keys are pressed in sequence (and rather slowly). (Some laptop keyboards with sysrq requiring fn require you to let go of sysrq while you press the other keys, in which case you hold down alt but alternate between sysrq and the other characters.)
Incidentally, for the grandparent: you probably want to write the whole sequence of 6 commands, R E I S U B, rather than just S U B. The R sets the keyboard to raw mode, sometimes allowing you to control-alt-f1 into a terminal and fix the crash without rebooting. E tells all the processes which are still running properly to terminate (many of them will save crash recovery or autosave data if you do that, so you can more easily get back to where you were); I kills all the processes that didn't shut down when you pressed E. This means that when you use S to synchronise the disks, it actually saves what you want to save, and nothing tries to queue up more data to save afterwards. Then U remounts filesystems readonly (or unmounts them; it comes to much the same thing), and B reboots the system instantly (the REISU do the rest of the shutdown process between them).
A good mnemonic for this is that REISUB is "busier" spelt backwards. (Raising Elephants Is So Utterly Boring is another common mnemonic.)
Sometimes I end up doing REISUO instead; unlike REISUB which is a manual reboot, RESIUO is a manual shutdown. It all rather depends on whether you want the system to stay down or come back up.
(1)DOCOMEFROM!2~.2'~#1WHILE:1<-"'?.1$.2'~'"':1/.1$.2'~#0"$#65535'"$"'"'&.1$.2'~'#0$#65535'"$#0'~#32767$#1"
You can use ALT-F4 instead - try it now.
AT&ROFLMAO
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You're hired! - Steve Jobs
While hooked up to a time share in the mid 70's, I wanted to know what the key did. I kept pounding it. After a few minutes, my display responded with ****STOP RINGING THAT DAMN BELL*****. Seems a large clanging bell in the server room, miles away, was hooked up so the System Admin could respond to requests from the user.
Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong fix.
Careful. I accidently typed Alt - SysRq - R + E + I + S + E + R and my wife disappeared.