Ask Klaus!

Knoppix 5.3.1

Question:

First, I would rather have sent an email to you at KNOPPIX, but I could not find an email address. I do not have actual Internet service. I only have this dial-up email account. I live in America, where the infrastructure to support technology does not exist in most places.

Yesterday I got the Knoppix 5.3.1 DVD as a cover disk for Linux Pro magazine. I immediately found that many of the programs either simply quit, or they lock up the computer such that only a reset is possible. It is not due to any errors reading the DVD. It is caused by Fusion.

To correct this, I have edited the xorg.conf file and changed to false the true in the line

Option aiglx "true"

Then I restart X.

This fixes most of the problems, but still KDE is not working the way it used to work.

Are there other things I must do to remove the effects of Fusion? (I suspect the KDE build was optimized for it.)

Answer:

Your computer seems to have a rare case of a graphics card that supports Composite+AIGLX (which is what Compiz needs), but the driver in xorg seems to be unstable for this specific chipset.

Booting with knoppix no3d will disable Composite, and therefore also Compiz, in xorg.conf. Also, you can manually disable Composite by searching for this section in xorg.conf:

Section "Extensions"
       Option "Composite" "Enable"
EndSection

Change to "Disable", or just remove the option, then you have to restart X.

Composite is probably the real problem here, not AIGLX itself, in that composite makes heavy use of the graphics driver's transparency feature. Newer KDE versions also check for Composite and use it for certain effects, such as transparent buttons; therefore, switching off AIGLX or not using Compiz won't help much.

An upgrade of your graphics card-accelerated xorg driver might help to get Composite working at a later time:

aptitude update ; aptitude install xserver-xorg-video-ati

(as an example for ATI cards), but for now, disabling Composite seems to be the safe option for your setup.

Unsupported Frequency

Question:

I work with two screens under Windows, but Linux says "Unsupported Frequency" and then turns one of the screens off. How can I work with two screens under Linux?

Answer:

It's not Linux that says "Unsupported Frequency," it's your monitor that does this and switches itself off afterwards. Just as you did when setting up the Windows driver for two monitors, you have to tell X server to use both monitors and the way you plan to do this (i.e., one monitor as an extension of the other, or parallel). The site http://gentoo-wiki.com/HOWTO_Dual_Monitors has a good description of how to do this.

Usually, you don't need a special "driver" for this, but you do need an entry in /etc/X11/xorg.conf.

Tale of Two Monitors

Question:

I have two monitors: a Samsung and Proview. I also have an Nvidia Geforce 7100 video card. The distribution I am using is Fedora 9 because it comes with the precompiled Nvidia drivers.

Fedora recognizes both monitors automatically, and what I want is to have two independent desktops.

If I go to the desktop configuration menu, it lets me activate the second monitor, but when I restart the graphical environment to activate the changes, everything goes back to the original settings. Can you give me a hand?

Answer:

If you want to have two independent desktops, you would use one monitor per graphics card, and you have to start one X server per graphics card. Note that this is different from using a dual-monitor setup to create a single huge "widescreen" desktop that spans across two monitors. For the latter, the website http://gentoo-wiki.com/HOWTO_Dual_Monitors has a nice description on how to accomplish this.

The reason activating the "two-monitor setup" you described fails to work might be because restarting just one X server is insufficient. Rather, you need to make sure that two X servers with two independent xorg.conf files are running – the first, for example, with:

Xorg -config /etc/X11/xorg-0.conf :0

and the second with:

Xorg -config /etc/X11/xorg-1.conf :1

To get the correct graphics cards (probably the PCI option in the Device section) running, you have to edit both xorg-0.conf and xorg-1.conf. Now, I don't know whether your Nvidia card is recognized as a dual setup. If so, it should show two entries in lspci -v. To get the PCI numbers for each xorg.conf, you can use the addresses shown by lspci -n, but it could also be that it's just not possible with this card.

If it is, or if you decide to install an additional card, you have to make sure that the display manager (XDM, GDM, or KDM) starts two X servers. Try to find the corresponding Xservers file for your display manager (updatedb ; locate Xservers) and add another line to start the second server:

/etc/X11/xdm/Xservers:
:0 local /usr/bin/X :0 vt7 -config /etc/X11/xorg-0.conf -nolisten tcp
:1 local /usr/bin/X :1 vt8 -config /etc/X11/xorg-1.conf -nolisten tcp

Next time XDM starts, it will run two X servers, each using one card with monitor attached and displaying a login window.

A problem I could imagine is trying to determine which keyboard and mouse is supposed to be the input device for which X server? To use this setup, you would need to install a second mouse and keyboard.

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    Klaus Knopper is the creator of Knoppix and co-founder of the LinuxTag expo. He currently works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com

  • Ask Klaus!

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  • Ask Klaus!
  • Ask Klaus!

    Klaus Knopper is the creator of Knoppix and co-founder of the LinuxTag expo. He currently works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com

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