CentOS virt - Feb 2015 - Video resolution for CentOS guest

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 out-of-date instructions for doing so.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.

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On 24/02/15 04:15 PM, Robert Nichols wrote:
> 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.
In my experience, once I set the resolution, it keeps that resolution
through reboots/logins. The initial login page sits at 1024x768, but
once logged in, it takes the resolution I asked for.

- -- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?
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On 02/24/2015 03:18 PM, Digimer wrote:
> In my experience, once I set the resolution, it keeps that resolution
> through reboots/logins. The initial login page sits at 1024x768, but
> once logged in, it takes the resolution I asked for.
It's working that way for me now that I have installed kernel-ml-3.19.0
from elrepo in the guest.  With the 2.6.32 kernel that CentOS 6
provides, the behavior could best be described as "confused."  I might
get a login screen at 1024x768 but with the content rendered as though
it were 1440x900 and the login dialog half off the edge of the screen.
Or, I might be logged in and looking at a screen properly drawn at
1024x768, but when I bring up the display preferences dialog it claims I
am already at 1440x900 and refuses to change.  And, occasionally when I
would try to change the resolution the display would lock up and, one
time, the whole X server crashed.

All that goes away with the guest running 3.19.0 kernel, and that also
makes sound work properly in the guest, so I'm happy now, at last.

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