[CentOS-virt] Video resolution for CentOS guest

Robert Nichols
Tue, 24 Feb 2015 21:15:25 -0000

On 02/23/2015 10:53 PM, Digimer wrote:
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> On 23/02/15 11:11 PM, Robert Nichols wrote:
>> Would someone please point me to some reasonably current
>> instructions for getting greater than 1024x768 video resolution for
>> a CentOS 6 guest on a CentOS 6 KVM/qemu host?  When I search online
>> I find stuff from 2009 and 2010 saying, "For details see
...," and
>> linking to a URL that no longer exists, or pages that say, "You
>> need to switch from VNC to Spice," and giving a long list of
>> out-of-date instructions for doing so.  (With virt-manager it takes
>> 2 clicks to do that.  Of course it doesn't help -- still maxes out
>> at 1024x768.)
>>
>> I've found that I can just append "vga=0x380" to the
kernel
>> command line and see Plymouth come up with the full graphical boot
>> screen in the correct 1440x900 resolution, but as soon as gdm
>> starts up, the display scrambles.  I find suggestions to generate
>> an xorg.conf file, but no mention of what to put in it.  I can run
>> "Xorg -configure", but the resulting file contains nothing
about
>> video modes, so it's not apparent what needs to be added.
>>
>> I find it particularly annoying that a Windows 7 guest can set any
>> resolution I want up to 2560x1600, but a Linux guest can't go
>> higher than 1024x768.
>
> I played with this and found that, in fact, I had to switch the spice
> / qxl. With that change, I had no trouble pushing EL6 to much higher
> resolutions.

Thank you for the reassurance that it _should_ work. I finally got it
going.  The VM still always starts out in 1024x768 and I have to set
the higher resolution every time I log in.  For a while, that was
working only the first time I set it, and on subsequent logins any
attempt to change the resolution either locked up or caused the Xorg
server to crash.  All the RPMs verified OK and a forced fsck of the
filesystems found nothing.  I eventually just reinstalled the whole
VM, and it's working now.

The whole thing was bringing back bad memories of an ancient version
of Slackware and kernel version 0.99pl53.

--
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.