Not fully supported graphics card
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Not fully supported graphics card
Sometimes one may purchase a new graphics card or complete system where graphics card is not supported by installed OS. In such cases one can install Cent-OS by choosing "Generic display driver" called vesa. To use generic display driver on a already running machine use following steps:
- Boot into single user mode
- Use command 'Xorg -configure' to create a 'xorg.conf.new' file in '/root' folder.
- If old graphics were working fine then take backup of '/etc/X11/xorg.conf' file appropriately.
- Replace '/etc/X11/xorg.conf' file with newly generated 'xorg.conf.new' file and restart the machine in run level 5.
- If things do not work then restart in single mode and edit the '/etc/X11/xorg.conf' file and replace all Driver lines with 'Driver "vesa"'
- Again restart the machine and check if things work fine.
Adding more display modes
Sometimes Linux may not recognize all the different display modes that are supported by a Graphics Card. For example at time of this writing Cent-OS 6.3 recognizes only 1600x900 resolution on Dell latitude E6430 laptops with Intel HD Graphics 4000 on-board graphics card. To add more modes one can use 'xrandr' and 'cvt' commands to add more modes.
Display all connected devices
To see all connected devices use:
xrandr --verbose
command. This will list all the connected devices and their recognized supported modes. This can also be done using GUI accessible at "System -> Preferences -> Display (gnome-display-properties)".
Creating new mode
To create a new mode first a mode-line needs to be constructed. Use:
cvt <width> <height>
For example,
cvt 800 600
This will result into a mode-line. Now a mode can be created with the mode-line output using
xrandr --newmode <MODE-LINE>
For example if the output of 'cvt 800 600' command is:
Modeline "800x600_60.00" 38.25 800 832 912 1024 600 603 607 624 -hsync +vsync
then use:
xrandr --newmode "800x600_60.00" 38.25 800 832 912 1024 600 603 607 624 -hsync +vsync
to create the new mode. Verify using 'xrandr --verbose' that new mode is created.
Now once a mode is created, it has to be added to the list of possible options for a given display using:
xrandr --addmode <device> <mode>
The device name is available in the 'xrandr --verbose' output as 'XYZ connected'. Typical device names are default, VGA, LVDS etc. Mode name is above case is "800x600_60.00". Mode names are also listed in 'xrandr --verbose' output.
Choosing a mode for display
To choose a mode for display once mode has been added one can use 'gnome-display-properties' or System -> Preferences -> Display menu option. Howover if use of command-line is preferred then command:
xrandr --output <device> --mode <mode>
can be used to change the mode using command line.
More information on configuring xrandr can be learned from https://wiki.ubuntu.com/X/Config/Resolution
