CentOS 7 + GUI As KVM Guest: Fix Screen Resolution

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Hi,

I’d like to run CentOS 7 in a KVM guest (host is my Slackware64 14.1
workstation). The main purpose of this installation will be to build custom RPM packages. I’ve made a few tests, and everything works more or less as expected. I’d like to resolve a small problem that’s nagging me though.

When I install a GUI, I usually start by installing a minimal system, then I add some command-line tools, then the X Window System, then I add a lightweight window manager like WindowMaker to configure X, and then only I install GNOME, the base desktop and only the applications I need. So far this works quite well.

I just made a first installation of CentOS + X11 + WindowMaker in a KVM
guest, and I have some small resolution problems. I have a twin-monitor setup, with the left 19″ monitor displaying the host system, and the right 19″ monitor the guest system. The “ideal” resolution for this type of monitor is 1280×1024.

Now when I start WindowMaker in the guest system, I get a weird resolution, something like 1024×600: looks like 1024×768, only it gets squashed down to what looks like 16/9. The top and bottom borders of the screen are black, a bit like a cinemascope movie.

Now I tried to make a second “vanilla” installation of CentOS in another KVM guest. This time I installed the default GNOME GUI. After the initial reboot, GDM has the same weird resolution (1024×600 I guess), and GNOME starts up with this same resolution also. BUT: I can go to the Monitor Settings, and define 1280×1024 as resolution, and this works perfectly.

Unfortunately this solution only seems to work on a per-user basis, and only in GNOME. So here’s my question:

– How did GNOME do that (redefine my monitor resolution on the fly)?

– Is there a way to achieve this new resolution system-wide, and also for WindowMaker?

I tried to fiddle a bit with xorg.conf (X -configure, copy it over, edit it), but to no avail.

Cheers,

Niki
—
Microlinux – Solutions informatiques durables
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One thought on - CentOS 7 + GUI As KVM Guest: Fix Screen Resolution

  • Le 25/05/2016 à 14:20, Nicolas Kovacs a écrit :

    I’ll answer that myself, since I just found the solution. It was as simple as this:

    # X -configure (without X started)
    # mv xorg.conf.new /etc/X11/xorg.conf

    Edit this file:

    Section “Screen”
    Identifier “Screen0”
    Device “Card0”
    Monitor “Monitor0”
    …
    SubSection “Display”
    Viewport 0 0
    Depth 24
    Modes “1280×1024”
    EndSubSection EndSection

    And that’s it. Works perfectly.

    Cheers,

    Niki

    —
    Microlinux – Solutions informatiques durables
    7, place de l’église – 30730 Montpezat Web : http://www.microlinux.fr Mail : info@microlinux.fr Tél. : 04 66 63 10 32