Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
Input Devices

Does Your PC Really Need a SysRq Button Anymore? 806

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."
This discussion has been archived. No new comments can be posted.

Does Your PC Really Need a SysRq Button Anymore?

Comments Filter:
  • Uhh, YES? (Score:1, Informative)

    by adosch ( 1397357 ) on Thursday January 14, 2010 @11:03AM (#30764162)
    Magic SysRQ key [] command for the *NIX world.
  • Terminals? (Score:4, Informative)

    by russotto ( 537200 ) on Thursday January 14, 2010 @11:04AM (#30764164) Journal

    I'm pretty sure SysRq is a left over from the terminal days, though I don't recall which terminal (the VT100 doesn't have it). It was basically the equivalent of CTRL-ALT-DEL.

    Ahh, Wiki to the rescue; it was from the IBM 3270.

  • by Aldenissin ( 976329 ) on Thursday January 14, 2010 @11:05AM (#30764196)

    I use the "busier" backwards or "reisub" combination with the sysrq key in order to gently shutdown Ubuntu when it locks up. So yes, I use it, but that has only been in the last couple of years or so. Not sure what else it is used for...

  • by djsmiley ( 752149 ) <> on Thursday January 14, 2010 @11:06AM (#30764204) Homepage Journal

    randomly I noticed that key earlier today, because some people have been given new usb keyboards instead of PS2 and they dont have that key (hp keyboards).... and now it appears here...


  • I've used it (Score:5, Informative)

    by jonbryce ( 703250 ) on Thursday January 14, 2010 @11:06AM (#30764218) Homepage

    If linux freezes, then Alt-SysRq-S+U+B will do an emergency sync of the disks, unmount them and reboot the system.

  • Re:Caps Lock Key (Score:3, Informative)

    by jonbryce ( 703250 ) on Thursday January 14, 2010 @11:11AM (#30764286) Homepage

    I use the Caps Lock for entering software serial numbers where you get a long string of capital letters and numbers.

  • by russotto ( 537200 ) on Thursday January 14, 2010 @11:12AM (#30764308) Journal

    ...Anybody know where I can find the sysrq key on it? :)

    It's the eject key.

  • Re:I've used it (Score:2, Informative)

    by Victor_0x53h ( 1164907 ) on Thursday January 14, 2010 @11:13AM (#30764326)
    I figured you were joking. "How do I hold all that down at once?" I thought.

    Alt+SysRq then press S, U, then B one at a time. R also looks like it might be necessary? []
  • Re:Print Screen (Score:3, Informative)

    by REggert ( 823158 ) on Thursday January 14, 2010 @11:20AM (#30764456)

    If you look at the pictures in TFA, you'll note that they've moved Print Screen to share space with the Insert key. To invoke Print Screen instead of Insert, you have to hold down the Fn key.

  • Re:Print Screen (Score:4, Informative)

    by Jaruzel ( 804522 ) on Thursday January 14, 2010 @11:20AM (#30764476) Homepage Journal

    Ditto. Alt+PrtScn is your current-dialog-capturing-friend!

    Although, it still amazes me the amount of people who still install 'freeware' utilities to take screengrabs of dialogs, when Windows has had that functionality built in for many versions... ... and I kid you not, I did once have this conversation:

    User: I need Photoshop CS2 installed, here's my Cost-Code.
    Me: Why?
    User: I write documentation that needs screenshots.
    Me: You know you can screengrab via windows and paste directly into Word?
    User: I don't care, Bob has Photoshop, and I want a copy as well.
    Me: *sigh* Ok, I'll buy a copy and charge your dept...


  • Re:Debug key (Score:4, Informative)

    by digitalhermit ( 113459 ) on Thursday January 14, 2010 @11:21AM (#30764492) Homepage

    Oh heck, I use the SysRq key on an almost daily basis whenever I screw up a kernel compile (and that's often). At least on my keyboards, it's on the same key as PrntScrn. Looking at my keyboard, there's nothing that I don't use on a fairly regular basis:Num Lk - *almost* always on when using a laptop. Almost always off when using a regular keyboard. Pause/Break I've mapped to bring up my task manager. I've also noticed that the paint is actually wearing off the hjkl keys on one keyboard (too much vi).

  • by thorsen ( 9515 ) on Thursday January 14, 2010 @11:23AM (#30764532) Homepage

    Sorry, but no you don't. You can easily use some set of modifiers for it instead. Win-space does nothing on my machine and is even easier to get to than SysRq because you don't have to move your hands from the normal position.

  • by singingjim1 ( 1070652 ) on Thursday January 14, 2010 @11:23AM (#30764540)
    Because the big delete key is actually the backspace key. Apple just had to be different I guess. The small delete key deletes stuff on the right side of the cursor. But I'm sure you already know this. I'm posting this for those that might not be familiar with what you are talking about.
  • by afidel ( 530433 ) on Thursday January 14, 2010 @11:23AM (#30764548)
    You can use numlock and the accessibility feature to use the number pad as a mouse, I do that with my wireless keyboard as using a wireless mouse on furniture sucks.
  • Re:I've used it (Score:3, Informative)

    by BESTouff ( 531293 ) on Thursday January 14, 2010 @11:27AM (#30764632)
    You don't. You keep Alt+SysRq pressed, and you press S, U and B in sequence.
  • Re:Debug key (Score:5, Informative)

    by ais523 ( 1172701 ) <ais523(524\)(525)x)> on Thursday January 14, 2010 @11:28AM (#30764654)
    This conflicts badly with Ubuntu's decision to make Alt-Sysrq+K the default way to kill X (as opposed to control-alt-backspace which is too easy to press by mistake), too.
  • by ais523 ( 1172701 ) <ais523(524\)(525)x)> on Thursday January 14, 2010 @11:31AM (#30764706)
    Although I've never used an old-fashioned typewriter, I have a old book teaching people how to use an old-fashioned typewriter. With the example keyboard layout it gives, the numbers start at 2; it recommends using l to type 1 and O to type 0 (as well as other fun combinations involving backspace to get a whole range of other symbols).
  • Re:I've used it (Score:5, Informative)

    by luder ( 923306 ) * <> on Thursday January 14, 2010 @11:32AM (#30764738)

    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.

  • Re:What key again? (Score:2, Informative)

    by mkettler ( 6309 ) on Thursday January 14, 2010 @11:35AM (#30764782)

    check your print screen button.

  • Re:I've used it (Score:5, Informative)

    by ais523 ( 1172701 ) <ais523(524\)(525)x)> on Thursday January 14, 2010 @11:38AM (#30764832)

    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.

  • Re:Print Screen (Score:2, Informative)

    by xtracto ( 837672 ) on Thursday January 14, 2010 @11:39AM (#30764850) Journal

    does Alt+PrtSc allow you to manually select any *section* of screen ?
    didn't think so..


    just WIN+R pbrush[ENTER] CTRL+V

    And use your mouse to select any section of the screen.

  • Chiclets (Score:3, Informative)

    by Dr_Barnowl ( 709838 ) on Thursday January 14, 2010 @11:43AM (#30764938)

    The real problem? This laptop has one of those horrible chiclet keyboards.

    Lenovo argues the new design gives the laptop a more "clean and inviting look"

    I don't want to use any keyboard where the look of the thing was given anything more than secondary consideration. I've used chiclet-keys on Powerbooks, and I hate them. And the stupid key layout. I understand that compromises have to be made on a laptop keyboard because of space, but the Powerbook keyboard seems to have been solely designed to "think different" from the standard layout. Thou Shalt Not Move The Slash Keys. Whenever I know I have to support one now, I take my USB keyboard with me, a nice Cherry G80-3000 with a boring, normal, sensible layout, and clicky key switches.

  • Re:Print Screen (Score:3, Informative)

    by JediTrainer ( 314273 ) on Thursday January 14, 2010 @11:44AM (#30764952)
    I don't even bother with that anymore. If you have it, OneNote puts a better screengrabber into Windowkey+S which lets you select the part of the screen that you want to capture (no more cropping!)

    I managed to get that part of OneNote working on Ubuntu as well, although through the tray icon instead of the hotkey. Unfortunately most everything else that I need in OneNote remains broken under the version of CrossOver I have.
  • by Dmala ( 752610 ) on Thursday January 14, 2010 @11:45AM (#30764976)
    I remember editing some documents for a woman who apparently learned this way. The problem is it looks OK in fonts like Courier and Times New Roman, but if you change the font they can stick out like a sore thumb.
  • by Omeganon ( 104525 ) on Thursday January 14, 2010 @11:52AM (#30765116)

    SysRQ can be extremely useful in figuring out why a machine has locked up or become unresponsive... []

  • by Z00L00K ( 682162 ) on Thursday January 14, 2010 @11:56AM (#30765200) Homepage

    Linux kernel developers also use that button.

  • by Anonymous Coward on Thursday January 14, 2010 @11:56AM (#30765210)

    ThinkPad jumped the shark when it was sold to the Chinese.

  • by OnlineAlias ( 828288 ) on Thursday January 14, 2010 @11:59AM (#30765272)

    SysRq is the print screen button, and I use it all of the time too. It is cut and paste for me, alt-printscreen (or control-printscreen) then shift-printscreen. Fastest screen paste in the west....

  • by lorenzo.boccaccia ( 1263310 ) on Thursday January 14, 2010 @12:01PM (#30765322)
    used countless time to fight against ati driver crashes under linux, using the old "reisub" sequence
  • Re:Mainframes (Score:3, Informative)

    by natehoy ( 1608657 ) on Thursday January 14, 2010 @12:22PM (#30765662) Journal

    Actually, I've been using a lot of 3270 emulators on various operating systems since Windows 3.11, and I have yet to see a single one that actually uses the physical SysRq key to mean SysRq. The old DOS ones did, but anything in Windows really can't, because SysRq causes a local interrupt that's harder to intercept. It's easier for emulator programmers to capture a less invasive keypress and simulate SysRq over the 3270 stream.

    My current 3270 emulator uses CTRL-ESC to emulate SysRq. I've seen a few others used as well. Actually, since the ESC key is meaningless over the 3270 screen, ESC itself is the ATTN/ClearError/ClearBuffer key.

    It's rather like the problem some operating systems have when using a remote desktop (VNC, Remote Control, etc). If you press CTRL-ALT-DEL, the emulator generally can't send that to the remote session because CTRL-ALT-DEL just caused a priority OS interrupt on the local machine and, depending on how your local OS handles CTRL-ALT-DEL, it may be rebooting. :)

    So most remote control software has a little button or control that says "send CTRL-ALT-DEL to remote".

  • by VertigoAce ( 257771 ) on Thursday January 14, 2010 @12:33PM (#30765862)

    Hold Alt, navigate through the menus with the keyboard, then press PrtSc.

  • by Chalex ( 71702 ) on Thursday January 14, 2010 @12:43PM (#30766070) Homepage

    The laptops that are getting this change are the Thinkpad Edge models. They are the low-end consumer level Lenovo laptops, Thinkpads in name only. They are not the regular Thinkpad T or X or R series models. The R series is discontinued now anyway. The regular T and X series are staying as they were (with minor modifications). You can read more details here:

    I look forward to the Thinkpad T series being the solid black square tanks that they have always been.

  • Re:Debug key (Score:5, Informative)

    by thebasicsteve ( 1672196 ) on Thursday January 14, 2010 @12:51PM (#30766196)
    Ubuntu didn't change the key. On any kernel with the "magic SysRq key" enabled (which Ubuntu has), Alt+SysRq+K kills all running processes on the current VT. Therefore, it kills X.
    Ubuntu's recent decision to disable Ctrl+Alt+Backspace by default is a separate issue.
    On older versions of Ubuntu, you will find that either key combo will kill X.
  • Re:Debug key (Score:3, Informative)

    by hson ( 78256 ) on Thursday January 14, 2010 @01:12PM (#30766588)

    Yeah, try that in Solaris and watch all processes die...

    killall is used by shutdown(1M) to kill all active processes not directly related to the shutdown procedure.

    Use pkill(1).

  • by miknix ( 1047580 ) on Thursday January 14, 2010 @01:19PM (#30766714) Homepage

    Used it a lot on my desktop when I hacked some scanner drivers to support my parallel port scanner. It is amazing the light show that a "simple" null pointer deference in your kernel driver can make. : )

    Also use it a lot to force buffers to flush to the disk and then remount the root filesystem as readonly. This was very useful to prevent disk corruption while I was debugging my ACPI suspend function on the laptop. For some reason (Microsoft ASL compiler) when the laptop was resuming from suspend state, the laptop LCD didn't turn on.

    I also noticed that some laptops have SYSRQ as a function (fn key). That way one has to press:
    fn+sysrq+ however, things start to be funny when these laptop also have a numeric keyboard available as second function in the {u, i, o, j, k, l, m} keys.
    For example: fn+i gives key 5.

    Now imagine fn+sysrq+u , one wanted a sysrq with command 'u' (remount root as ro I think), but will get a sysrq with command 5 (change log level I think). Yikes!

  • by Anonymous Coward on Thursday January 14, 2010 @01:20PM (#30766732)

    The new ThinkPads all include this BIOS swapping option.

  • Re:Debug key (Score:4, Informative)

    by colin_s_guthrie ( 929758 ) on Thursday January 14, 2010 @01:58PM (#30767382) Homepage

    I think you're confused. Alt+SysRq+K is one of the Linux "Magic Keys" [] it kills all processes on the current VT, not just X. Most modern X implementations will still work with Ctrl+Alt+BkSp but you now need to do it twice and the first time it makes a rather ominous "beeeeeeeeeep" at you to warn you that you maybe about to make a bad decision....

    So this is hardly an "Ubuntu decision" (like most distros they just package up what's already there, mix it up with a few good and a few bad ideas of their own and paint it nicely).

  • Re:Say what? (Score:3, Informative)

    by noidentity ( 188756 ) on Thursday January 14, 2010 @02:10PM (#30767660)

    No - since I own a insensitive bork........

    Then you have the Programmer's Key [], though it was removed from Mac designs around 1995, replaced with the Command-Power combination, or on later Macs with USB keyboards, Command-Eject.

  • by Anonymous Coward on Thursday January 14, 2010 @02:23PM (#30767880)

    If you're using windows, they have an on screen keyboard that can send any keystroke you wish regardless of the keys on your keyboard. Its really handy in situations where your laptop keyboard is missing a few keys already before this change.

  • Re:Debug key (Score:4, Informative)

    by bcmm ( 768152 ) on Thursday January 14, 2010 @03:47PM (#30769480)
    They are not actually the same. Ctrl-alt-backspace tells X to quit, which it will do if it's actually well enough to listen. Alt-SysRq-K is a key combo for the kernel, and tells it to kill everything running on the current virtual console (originally so that you could make sure you were typing your password into the getty instead of into a program another user had left running to phish login details).

    This has the advantage that it will always kill X, even if X has hung (and will always give you your display back unless the graphics driver has left the adaptor in a weird state), and can also kill whatever (graphical) program had made the system unresponsive, even if it's malfunctioned badly enough to continue eating resources after losing it's connection to the X server.
  • by humdinger70 ( 325597 ) on Thursday January 14, 2010 @04:46PM (#30770390)

    The SysReq key goes back to the IBM System/360 mainframe. It didn't have a CRT as the operator console, it had a modified IBM selectric typewriter-type (with the patented ball type element) as the operator console. It was a model 1052.

    Because of the slow print speed (less than 15 characters per second), the mainframe OS could spew out a lot of messages (some cryptic in nature to someone not familiar with the system) on paper. In order to prevent confusion, the keyboard was locked by default and you had to press the SysReq key on the keyboard and wait for the system to unlock the keyboard (and that might take a bit) to allow the operator to enter commands.

    I actually saw one in use at a PPOE, on an IBM System 360/50. You just had to live with it.

    The next generation IBM System 370 systems initially came with the same type of console, but they later introduced the much faster 3215 console keyboard/printer, which I think used a dot-matrix type print element. Still had to use the SysReq key to be allowed to enter commands.

  • by Impy the Impiuos Imp ( 442658 ) on Thursday January 14, 2010 @04:50PM (#30770466) Journal

    I am old enough to remember that the Scroll Lock key actually did lock the scrolling of an old text-based terminal window. They didn't even have a buffer to "scroll" back up, so if you needed to see something, it was that or forget it.

    It basically froze the entire computer and stopped processing. You can see a modern analog of that in a Windows "DOS" window (do a "dir" on a large directory). Scroll Lock doesn't work, but you can use the mouse to "select" a bit of text while it's moving and the whole thing halts, including any computation from that window.

    I never knew what SysRq did, though :)

  • Re:Debug key (Score:3, Informative)

    by marcansoft ( 727665 ) <(hector) (at) (> on Thursday January 14, 2010 @05:01PM (#30770650) Homepage

    Ubuntu's recent decision to disable Ctrl+Alt+Backspace by default is a separate issue.

    It wasn't Ubuntu's decision, it was Xorg's. I had to explicitly map Ctrl+Alt+Backspace again under Gentoo after a recent Xorg update.

... though his invention worked superbly -- his theory was a crock of sewage from beginning to end. -- Vernor Vinge, "The Peace War"