Brice Goglin's Blog - Debian/X.org notes - X behavior changes in experimental

Feb. 14th, 2009

10:25 - Debian/X.org notes - X behavior changes in experimental

Apart from interesting features such as DRI2, KMS or input-hotplug, there are some minor changes in X in experimental that actually appear to disturb many users.

The first one is that Ctrl-Alt-Backspace does not kill X anymore. There is no easy consensus here, but many people were annoyed of killing X by mistake, so it's disabled by default now. To reenable it, add to the ServerFlags section of your xorg.conf:

        Option "DontZap" "off"

Another one is the background during X startup. Say goodbye to the old well-known grey background. Now you get a black background by default. To revert to the old behavior, pass -retro on the server command line (for instance in /etc/X11/xinit/xserverrc). Note that this option also reenables Ctrl-Alt-Backspace killing the server.

Finally, you might also see glxgears reporting very low frame rates (60) on some hardware. Well, please remember that it is not a benchmark, the output basically means nothing. This is why some distros even removed the fps output by default. The thing is that recent DRM stacks will just synchronize frame rendering on vertical blanks (can anybody here see 1000fps with human eye?). So if you have a 60Hz refresh rate, glxgears will report 60fps, that's it. But it has nothing to do with DRI or 3D being slow. Please try some relevant 3D programs or benchmarks before complaining :)

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Tags: debian, planet.d.o, xorg

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Comments:

From:	joey.kitenet.net
Date:	February 14th, 2009 16:32 (UTC)

dontzap and security

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AFAIK, the only secure way to log into X is to press ctrl-alt-backspace first.

Otherwise, you have no guarantee that the login window you type your password into is legitimate, and not an evil program left running by the last user to log into X.

So, what's the rationalle for removing this security feature? (Besides people being idiots with the keyboard.)

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From:	(Anonymous)
Date:	April 11th, 2009 08:02 (UTC)

Re: dontzap and security

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You can still use the secure access key of the kernel, which kills all processes on the current VT: Alt-SysRq-K.

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From:	(Anonymous)
Date:	February 14th, 2009 16:34 (UTC)

Really?

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Does this mean that Ctrl-Alt-F1 etc won't work by default either?

Who are those "many people" who keep hitting Ctrl-Alt-BS by mistake? That certainly never happened to me... Meanwhile, I use Ctrl-Alt-F1 and even Ctrl-Alt-BS rather often when some things go wrong inside X (for example to kill a process when the GUI is no longer responding, or even nuke the whole session as a last resort to get out of an OOM situation that would otherwise render my system unusable for 30 minutes or require a hard reset).

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From:	(Anonymous)
Date:	February 14th, 2009 20:38 (UTC)

Re: Really?

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Ctrl-Alt-F1 still works as usual. Only Ctrl-Alt-Backspace is disabled.

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From:	mrmeval
Date:	May 25th, 2009 19:43 (UTC)

Re: Really?

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They're the mAsses that xorg and ubunto is catering to now. There is no single simple server configuration anymore. Dontzap alone will not work. CTRL-ALT-Fn may not work. This has been buried in xkb but no one at xorg or Ubuntu so far are willing to offer documentation. I'm giving Fedora a try as they may have a fix or have hacked simple DontZap feature back into the server.

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From:	(Anonymous)
Date:	February 14th, 2009 20:24 (UTC)

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Speaking as someone who always turned DontZap on in xorg.conf, I greatly appreciate this change. I often use Ctrl-Backspace to delete a word, and on keyboards with Ctrl and Alt right next to each other it doesn't take much to unintentionally include Alt in that keystroke, killing the server.

However, with the advent of kernel modesetting, perhaps Ctrl-Alt-Backspace could become a little more sane: when hitting Ctrl-Alt-Backspace, switch to something independent of X and prompt whether to restart the server or not. Perhaps the same prompt could offer an option to log in on another terminal.

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From:	(Anonymous)
Date:	February 15th, 2009 10:57 (UTC)

black by default

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"Say goodbye to the old well-known grey background. Now you get a black background by default."

Why black? Wouldn't it just look like the graphic card failed to initialise? At least when the previous gray background would show up one would know that X worked...

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From:	mrmeval
Date:	May 25th, 2009 19:39 (UTC)

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Dontzap is ignored. So far Fedora seems to be the only distro with a fix.

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