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    G-AVLN in front of her home

    Mostly Unix and Linux topics. But flying might get a mention too.

    Tuesday, February 05, 2008

    Making the best of VESA drivers in CentOS 5

    Teaching in Edinburgh, on machines that flatly refuse to switch between CLI and GUI. Going into any of the CLI (CTRL_ALT_F1 - F6) is no problem, but restarting the X server or switching back from CLI gives random, hardly ever successful results.

    Last week a couple of colleagues (Donald and Gary) were saying about dropping resolution, this week one of our techies (Stuart) found advice about vesa. Neither approach worked on its own, but put them together (albeit in a slightly modified way) and all is well.

    If your GUI is working


    System --> Administratio
    n --> Display (may need to put root's password if logged in as ordinary user)
    Select Hardware tab
    Configure "Monitor Type" to Generic LCD --> LCD Panel 1024 x 768
    Configure "Video Card" to "vesa - Generic VESA-compliant video cards"
    Do the OK three times.

    I always check the config on RHEL/CentOS before restarting the GUI. Either look inside the configuration file (/etc/X11/xorg.conf, attached below) or check the System-->Administration-->Display-->Hardware settings (note that the vesa driver will be described as "Unknown video card").

    To restart the GUI press CTRL-ALT-Backspace - all should be well.

    If your GUI is NOT working

    If the GUI is broken to the point you can't use the method above, you can hack the file directly, or enter the configuration screen from the command line. For that, log in as root on CLI (enter CLI with CRTL-ALT-F1), then enter:

    # system-config-display

    The system will use basic GUI settings to 'draw' the menus. Use the solution as provided above to complete the steps.

    To start the GUI, the cleanest method I found is to 'recycle' runlevels: change into runlevel 3, then into runlevel 5.

    # init 3
    Several messages will be printed, when you see one fron "anaconda" hit enter. That will re-print the prompt. Now type:

    # init 5

    XWindows should start successfully!

    sample /etc/X11/xorg.conf using defaults for both the server and the monitor
    Section "ServerLayout"
    Identifier "single head configuration"
    Screen 0 "Screen0" 0 0
    InputDevice "Keyboard0" "CoreKeyboard"

    Section "InputDevice"
    Identifier "Keyboard0"
    Driver "kbd"
    Option "XkbModel" "pc105"
    Option "XkbLayout" "gb"

    Section "Monitor"

    ### Comment all HorizSync and VertSync values to use DDC:
    ### Comment all HorizSync and VertSync values to use DDC:
    Identifier "Monitor0"
    ModelName "LCD Panel 1024x768"
    ### Comment all HorizSync and VertSync values to use DDC:
    HorizSync 31.5 - 48.5
    VertRefresh 40.0 - 70.0
    Option "dpms"

    Section "Device"
    Identifier "Videocard0"
    Driver "vesa"

    Section "Screen"
    Identifier "Screen0"
    Device "Videocard0"
    Monitor "Monitor0"
    DefaultDepth 24
    SubSection "Display"
    Viewport 0 0
    Depth 24
    Modes "1024x768" "800x600" "640x480"

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