Slashdot Mirror
The Guy Responsible For Ctrl-Alt-Del
Gannett News is running a story about David Bradley, the IBM engineer who, in 1980, coined Ctrl-Alt-Del. Interestingly, he meant for it to remain a developer-only tool, not something for end users, and certainly not to have Windows users change their passwords or logoff. He also says he chose those keys specifically as it's not a key sequence that can be struck by accident.
....from the article:
> He's much too modest. Would Alexander Fleming
> have said, "It wasn't a memorable event," when
> he discovered penicillin?
Crikey.
The Army reading list
Just imagine how much in royalties this guy could have made if he had developed that nowadays with our patent frenzy attitude!
Rich, he would have been rich I tell you!
Mod me down with all of your hatred and your journey towards the dark side will be complete!
As a tech support guy, I just want to give this man a hearty "Thank You"
"I don't have a control key. I have an alt key and this little wavy square, and next to that is a curtl key. And I hit that and backspace and it doesn't do anything."
Thanks, man.
(ps: yes, I know he didn't intend it for the end user. It's a JOKE. Read it, chuckle, give me mod points, and move on)
Pulp Audio Weekly - Geek News and Reviews
Ctrl-Alt-Del is the only key combination on your computer that has its own hardware interrupt (similar to Ctrl-Open Apple/Closed Apple-Reset on Macs). Again, this was to prevent interception in real mode, however protected mode changes all rules.
Try not. Do or do not, there is no try.
-- Dr. Spock, stardate 2822-3.
When quake first was released, i didn't want to use the mouse, only the keyboard. However, after doing the shoot-strafe-left-look-down maneuver one time too many, i decided to switch to mouse... (shoot-strafe-left-look-down = ctrl, alt(gr), left arrow, delete)
Who is he kidding? Just the other day, my gorillas and I were playing soccer in the lab. Why we must of hit ctrl-alt-del over a hundred times just in the first half. After that, we moved the game over to the kitchen, just to be safe.
uh huh...
oh please. He picked a key sequence that's difficult to accidentally set off. So what? It could have been shift-esc-break. If this is what a Ph.D. in electrical engineering is good for, I'm glad I don't have mine.
And the reason MS used it for login in NT 3.1 was for security. It negated the possibility of a impersonation client that displayed an image which looked like the NT 3.1 login, but just stole Passwords instead. If such a client was written to DOS or Windows it would simple reboot. So it was a sanity check, at the time.
-Malakai
A Dragon Lives in my Garage
Many people rag on this, but it actually made some sense at the time. Microsoft has removed it from later versions of Windows for convenience, not security, purposes.
For people who don't know, WIndows NT 4 (and perhaps 3.5 and earlier?) required one to hit CTRL-ALT-DEL to get a login prompt. Many people complained, not seeing the logic in it, but logic there is.
CTRL-ALT-DEL is can never, ever be trapped by an application -- unless Windows has hosed completely, it's guaranteed to get the OS's attention. Having to hit it to get a login box means that no other application can fake a login box. If they tried, CTRL-ALT-DEL would bring up the task manager instead of a login dialog.
So regardless of whether you like it, the minor annoyance served a good purpose and was actually a fairly clever design decision. Much smarter than, oh, allowing macro viruses to execute by default.
This isn't as much "normalization" as it is "don't take so many drugs when you're designing tables."
Bradley says the "strength of the country" is at stake because relatively few students go into science or technology
Why should they when engineers can't find jobs, salesmen are making 6 figures and MBAs are stealing all the money.
Why is it that everyone thinks that Ctrl-Alt-Del has some special hardware interrupt, or something else that makes it magical?
The BIOS traps that combination (through the normal keyboard interrupt) and initiates a system reboot.
Problem is, if your OS isn't using the BIOS for keyboard input (pretty much every modern OS uses it's own keyboard handling code) then the OS determines what this key combination does.
In either case, it is software that determines what that key combination does.
--
"What do you want me to do? Whack a guy? Off a guy? Whack off a guy? Cause I'm married."
...but there's a reason why Windoze uses that for logging in. That is, that key combo cannot be intercepted by applications thus making it impossible to create infamous fake logins for grabbing user credentials mere looks-like-login-screen. Naturally such preventive measures could've been done a bit more elegantly than just using ctrl-alt-del to log in, but still, it's a very windowsy way of overcoming obstacles.
In many unix systems however, there are little or no protection for fake-login local attacks, eventhough preventive measures would be quite easy to implement using some key combo deemed ungrabbable by user software (little like say ctrl-alt-backspace is in X). It's all too easy to display a xdm/gdm look-a-like screen on university/public-office displays and grab logins and then display some sort of segfault crap an logout back to the real xdm/gdm. Average (l)user hardly takes much of a notice.
1 Earth is warming, 2 It's us, 3 it's royally bad, 4 we need to take action NOW
I actually saw a video clip on Tech TV with him and Bill Gates (and someone else but the name eludes me for the moment). They were in some sort of conference and he goes (not a word-for-word quote)"Yes well I'm the one who created CTRL-ALT-DEL, but Bill here is the one who made it famous" ... rousing laughter from the crowd, Bill has the embarassed grin on his face. He allows the laughter to die a little and says "...For Windows NT log-ons!" it was a CLASSIC moment.
From when Win95/98 reigned supreme - CtrlAltDel stick!
Black holes are where God divided by zero
It still needs reboots. It acts better once rebooted. In generalm Win2k and XP get alower the longer they run, and start experiencing problems like randomized icon images, windows that don't redraw, loss of fonts, etc. A reboot fixes all. When my Win2k laptop gets to where it's using >350MB of RAM, and I've closed all the apps, it's asking to be rebooted.
Napster-to-go says "Fill and refill your compatible MP3 player", which is a lie. It's not MP3. It's WMA with DRM.
I can vivedly remeber unpacking my first Macintosh, must have been 1984 or something. The package included a little, user installable switch, and this is what the Mac Handbook had to say about it:
"Programmer's Switch
The switch causes a reset or an interrupt. If you do not know what a reset or an interrupt is, you do not need it."
I could not have said it better...
Alex
Absinthe makes the heart grow fonder
SysRq was the original interrupt-generating special keystroke. It doesn't get much use anymore, though.
HIV Crosses Species Barrier... into Muppets
Well, aside from your comment indicating you to be a total jackass, there is actually a good reason behind the CTRL-ALT-DEL sequence in NT. It's a security feature.
"The CTRL-ALT-DEL key combination in NT disables user mode programs so a trojan program cannot intercept the user's name and password during the logon process. No user mode programs can be run until a valid logon has occurred. This is called restricted user mode. The CTRL-ALT-DEL key sequence indicates that there is a physically connected keyboard that the keystrokes are coming from. During the logon process, the Winlogon service passes the user's point of authentication, name, and password to the client/server (CSR) subsystem. The CSR passes the information to the security reference monitor which checks the Security Accounts Manager (SAM) database against the received information to see if the user is authentic. If so, a valid access token is generated and returned back down the line to the processes that sent the information."
Read more here.
I should really get some work done...
Buy the President
ca::ctrlaltdel:/sbin/shutdown -r now
Yep...you might recognize that as the reboot command. You can go ahead and change it so that it shuts down your computer or run anything else you desire (although it'll run it with root privileges so, don't put something stupid in there unless you're running Lindows and therefore are always root, I guess)
Warning: Opinions known to be heavily biased.
David Bradley, I give you a three finger salute. Microsoft, I salute you as well, minus two fingers.
So, this guy thinks that too few students are going for science or technology degrees? I wonder why... lets see, scientists dont make much. Manufacturing is moving to the third world, and taking a hell of a lot of engineering jobs with it. IT is moving to India. Yeah, I'd be sure to pick one of those fields if I were trying to decide on a major. You can't blame the students for the decline in "the strength of the country", they're just looking out for themselves and trying to pick a career that might actually have a future.
I have never came across more unergonomic key sequence than Control-Shift-Esc.
Obviously, you're not an EMACS user.
Ok, so I didn't read all of it either, here's howto and ahy to use sysrq under linux 2.6
/proc/sys/kernel/sysrq
/proc/sysrq-trigger. eg:
/proc/sysrq-trigger
:-)
:IMPORTANT :IMPORTANT
/usr/linux-beta/Documentation/sysrq.txt
Edit ed for lameness, have fun
"Linux Magic System Request Key Hacks
Documentation for sysrq.c version 1.15
Last update: $Date: 2001/01/28 10:15:59 $
* What is the magic SysRq key?
It is a 'magical' key combo you can hit which the kernel will respond to
regardless of whatever else it is doing, unless it is completely locked up.
* How do I enable the magic SysRq key?
You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when
configuring the kernel. When running on a kernel with SysRq compiled in, it
may be DISABLED at run-time using following command:
echo "0" >
Note that previous versions disabled sysrq by default, and you were required
to specifically enable it at run-time. That is not the case any longer.
* How do I use the magic SysRq key?
On x86 - You press the key combo 'ALT-SysRq-<command key>'. Note - Some
keyboards may not have a key labeled 'SysRq'. The 'SysRq' key is
also known as the 'Print Screen' key.
On SPARC - You press 'ALT-STOP-<command key>', I believe.
On the serial console (PC style standard serial ports only) -
You send a BREAK, then within 5 seconds a command key. Sending
BREAK twice is interpreted as a normal BREAK.
On PowerPC - Press 'ALT - Print Screen (or F13) - <command key>,
Print Screen (or F13) - <command key> may suffice.
On other - If you know of the key combos for other architectures, please
let me know so I can add them to this section.
On all - write a character to
echo t >
* What are the 'command' keys?
'r' - Turns off keyboard raw mode and sets it to XLATE.
'k' - Secure Access Key (SAK) Kills all programs on the current virtual
console. NOTE: See important comments below in SAK section.
'b' - Will immediately reboot the system without syncing or unmounting
your disks.
'o' - Will shut your system off (if configured and supported).
's' - Will attempt to sync all mounted filesystems.
'u' - Will attempt to remount all mounted filesystems read-only.
'p' - Will dump the current registers and flags to your console.
't' - Will dump a list of current tasks and their information to your
console.
'm' - Will dump current memory info to your console.
'v' - Dumps Voyager SMP processor info to your console.
'0'-'9' - Sets the console log level, controlling which kernel messages
will be printed to your console. ('0', for example would make
it so that only emergency messages like PANICs or OOPSes would
make it to your console.)
'e' - Send a SIGTERM to all processes, except for init.
'i' - Send a SIGKILL to all processes, except for init.
'l' - Send a SIGKILL to all processes, INCLUDING init. (Your system
will be non-functional after this.)
'h' - Will display help ( actually any other key than those listed
above will display help. but 'h' is easy to remember
* Okay, so what can I use them for?
Well, un'R'aw is very handy when your X server or a svgalib program crashes.
sa'K' (Secure Access Key) is useful when you want to be sure there are no
trojan program is running at console and which could grab your password
when you would try to login. It will kill all programs on given console
and thus letting you make sure that the login prompt you see is actually
the one from init, not some trojan program.
IMPORTANT:In its true form it is not a true SAK like the one in
IMPORTANT:c2 compliant systems, and it should be mistook as such.
It seems other find it useful as
thank God the internet isn't a human right.
I mean, why isn't there a Ctrl-Alt-Gateway or Ctrl-Alt-Compaq? What makes Dell so special?
--Joe
If you're going to get to that level of detail, shall we discuss the (in)stability of Gnome/KDE? It seems all to convenient that when Slashdotters define "Windows crashing", it includes any operational glitch at all, but "Linux crashing" seems to be confined to kernel panic only.
The vid of Bradley vs. Gates. Hilarious!
Life is the leading cause of death in America.
This feature is properly known as a SAK - Secure Attention Key. It's an old security feature used to prevent hijacking of trusted consoles, as you said, and is implemented on many systems. The perennial place where it's needed is university computer labs, where logging in and then leaving a fake login prompt running to capture passwords is has always been considered good clean fun. (To implement it properly, one should print a "wrong password!" message, and then exit the user session completely giving the user the real login prompt)
The basic idea is that the OS traps the SAK and does something obvious (like give you a login prompt) to keep a user from running a program pretending to be the OS. Since the OS doesn't let the user handle the SAK, security is maintained.
Linux supports SAK, however it's never really been properly deployed by distributions. Part of the reason is that nobody's ever really standardized on what the SAK key should be. If SysRQ is enabled, than Alt-SysRQ-k will cause a SAK event in the kernel. Otherwise, the keyboard driver can be configured by root to use any key sequence. One key sequence I've seen used is Alt-SysRQ-PageDown, but there's really no particular standard.
When SAK is raised in linux, all programs running on the current terminal are force-killed. It's then expected that init will provide a new login prompt there.
This leads to the second problem with SAK on Linux, namely that most users run X on workstation machines. If you SAK while X is running, the kernel kill -9's X... Which trashes your video card, leaving the system in an unusable state. Which is probably not what you wanted. Some video drivers and cards in X may be stable enough that, if you're running xdm/gdm/kdm etc., it may be able to restart X and give you an X11 login prompt - but the console will still be trashed, so you won't be able to exit out of X afterwards (or eg. with ctrl-alt-f1). It used to be the case that you could store the video settings for your console and run a program (eg. restoretext etc.) to fix them, but that hasn't worked on any modern video card in years. In addition, if you just escape out of X and then fix the console, X will re-trash your console as soon as you return to it, since it only stores the console settings from when X was started, not the current settings. Hence, X and your console program get in a fight and you probably end up crashing the video card and having to pull the power plug out or something if you do this a lot.
Confusing things even more, XFree generally defines its own internal "SAK"-like key sequence, Ctrl-Alt-Backspace. This isn't actually an OS-level SAK though, it just instructs X to quit. And not surprisingly, it often doesn't work due to XFree bugs (and may be trappable by user apps).
On the original PC keyboard there were only 83 keys. There was a single CTL key, a single ALT key (above and below the left hand shift key respectively) and a single DEL key (on the far right of the keyboard, just to the left of the big + key). I'd post a picture if I knew how. So it was definitely two handed.
There were 8192 bytes available for the IBM PC ROM BIOS. We used about 8180 of them. Two of the keys needed to be shift keys (for code conservation) and I picked the "newest" shift keys. The third key was picked to be as far away as possible, and "DEL" was a better mnemonic than "+".
is written. It's a revelation to some but people like Tolkein, King, etc often don't really know, beyond the inital premise, what's going to happen in their stories. In Stephen King's "On Writing" he claims a creative process that is more discovery than anything else. There isn't an all-encompassing outline drafted ahead of time. He starts out with an idea like "what if there was a cemetary that brought people back to life" and proceeds from there. He likens it to simply catching the story on paper as it falls out of his head. I don't know if this is what Tolkein was talking about but it works for alot of people.