Tuesday, August 21, 2007

force VGA screen resolution and screen mode

As included from previous blog entry of changing VGA setting or VGA screen resolution using Gnome system-config-display, which can be found here, here's another entry on how to force VGA screen resolution into your X settings directly via terminal.

As you know, X uses default configuration files, one of them is /etc/X11/xorg.conf. X reads this file during the process of launching and logging into X via runlevel 5. Settings for mouse, keyboard, VGA card, display resolution, regional language, screen types, VGA drivers and other modules used by X are basically declared and can be found from this X conf file.

If you want to change your VGA settings directly via terminal or force screen VGA resolution changes due to some *unknown driver issues, you can edit this file directly. Remember to do proper backups when editing linux configuration files.

1. Backing up xorg.conf

# cp /etc/X11/xorg.conf /etc/X11/xorg.conf.good

2. Launch your favorite terminal editor and edit xorg.conf

3. Inside xorg.conf, find the "Section Screen" which declares supported screen resolution for your currently detected VGA card. A sample of screen section layout is shown below:

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 16
SubSection "Display"
Viewport 0 0
Depth 16
Modes "800x600" "640x480"

If you strongly believe and have proof that your VGA card supports a non-declared screen resolution besides from the above shown modes or if your VGA card driver manuals or websites showed that your VGA card supports the screen resolution you wish to achieve, proceed with the following with caution.

4. Here, assuming that we are going to force a VGA screen resolution mode of 1024x768 into xorg.conf and you are done with xorg.conf backup file. Edit the xorg.conf lines that says 'Modes' under Screen Section like shown below

Modes "800x600" "640x480"

Modes "1024x768" "800x600" "640x480"

and save xorg.conf.

5. Close all opened applications. Restart X by hitting Ctrl+Alt+Backspace key combinations and see the effects of xorg.conf changes.


If X hangs after giving it some time like 60 seconds or more, and you wish to revert back recent changes from your xorg.conf, simply press Ctrl+F1 and login as root via TTYs. Then copy your backup xorg.conf.good file overwriting the non-working xorg.conf. Go back to X mode by hitting Ctrl+F7 and from there, try to hit Ctrl+Alt+Backspace for another X restart attempt.


If X does not restart again, try to go back to currently logged in root user via Ctrl+F1. As root, issue one of the following to stop a malfunctioning X or restart a new process from one of the below X commands.

To stop X
# gdm-stop

To restart X
# gdm-restart

To have a safe mode restart of X
# gdm-safe-restart

To launch a new X
# startx

There are times you need to kill an existing non-functioning Gnome X process by using kill.

Gnome X has a feature of detecting non-responsive and redundant failed launchng of Gnome X. If any attempts to launch X failed for several consecutive times, Gnome X automatically prompts you to have a new X setup and launches a new X setup. This is the same like launching it during a fresh linux installation.

This works for me during my old laptop, I hope it works for you too with your Fedora boxes as well.


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