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Re: [Xen-users] Sup guys, I'm a Xen noob, I have plenty of questions...

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Subject: Re: [Xen-users] Sup guys, I'm a Xen noob, I have plenty of questions...
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Wed, 2 Apr 2008 16:10:42 +0100
Cc: trist007 <thartanian@xxxxxxxxxxx>
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> xen and virt-manager.  I rebooted to the xen os.  When I booted into the
> Desktop, I noticed that my windows were all out of whack (I have compiz
> fusion installed on my regular Fedora 8 OS).  So I deactivated desktop
> effects and everything worked fine.  I noticed that my kmod-nvidia driver
> was no longer installed.  Can you guys explain what this OS is?  It seems
> to be a duplicated of my normal Fedora 8 OS but only that my nvidia driver
> isn't loaded. 

When you boot normally, you're running Linux on the bare metal hardware.  When 
you boot into the Xen-enabled system you're running XenLinux in a paravirtual 
machine on top of Xen.  The virtual machine that comes up when you boot the 
system (the one you see start up and that you are interacting with) is 
called "domain 0" - it's privileged to access all the hardware, so it looks a 
lot like your normal OS.

Because you're running paravirt Linux, a different kernel is used.  NVidia 
haven't supported their kernel module for running under XenLinux so that's 
why your 3D acceleration is broken and the module not loaded.  2D 
acceleration should still work.

Some people have had success with patching NVidia's module wrapper code and 
recompiling it in order to get 3D running in dom0, so that might be worth 
trying at some point.

> So, if I wanna run an OS and a virtual OS, I have to boot up 
> to this OS? the one with xen at the end?  I tried installing the
> kmod-nvidia driver but it didn't install because it said that the kernel
> was already installed.

You need to use the Xen-enabled boot option to start Xen and XenLinux.  This 
is just starting your normal Linux distro with the difference that it's 
running Xen and a XenLinux kernel instead of a standard bare metal Linux.  
Does that make sense?

> Ok, so I used the gui virtual machine manager and created a virtual OS of
> Fedora 7, I made it paravirtual, gave it 10GB, and 512MB of Ram, and
> created a virtual network.  After it installed I could see the blue
> console.  Now I'm a bit confused.  Is the Installation complete? 

"Blue console" sounds like the text-mode stages of the installation process.  
virt-manager sets things up so you have to run through an Anaconda-based 
installation process, just as you would have to for a physical machine.

You need to supply it with a network path for it to install from; after that 
it'll start up the friendlier graphical Anaconda installer and you can set up 
all the things you need before running through a (relatively) normal 
installation process.

> So I
> rebooted the computer back to the original Fedora 8 OS.  I try using virtual
> machine manager, but it won't connect, it says that my libvirtdaemon hasn't
> started.

virt-manager will only work for Xen virtual machines when your computer is 
booted into Xen.

> So I reboot to the Fedora 7 xen OS.  I go to
> virtual machine manager and try to connect to my virtual os.  It starts up
> and it says it's running, but there's no cpu usage.  I check the console,
> and it says it's currently unavailable.  It won't let me pause the virtual
> os, says that the POST operation failed, bootloader didn't return any data.
>  What do I need to do to get the virtual os to start running again?

Sounds like the install failed.  Just delete that OS and start an install 

> I'm just confused.  I wanted to use a
> virtual os to setup and ftp server, but I just don't see how one can do so
> with that blue console.  I'm obviously missing something.  Should I have
> gone virtual instead of paravirtual?

You could do, but it's not really necessary for a Xen-aware Linux distro like 
Fedora, since it already has good support for running paravirt.  Fully 
virtual is useful for running operating systems without Xen support (such as 

> Also, I've heard that once I get the 
> virtual os running, I can switch between my regular Fedora 8 OS and my
> virtual Fedora 7 OS with a simple click of the mouse.  Is this true with
> Xen or should I use another virtualization program.

By default, virt-manager will display your OS in a window like an application.  
You can fullscreen that window although the version I use doesn't scale up 
the VM's display to fit your screen.

You can also configure things so that you can use any VNC viewer you want to 
view the virtual machine's screen.  I've enjoyed using KDE's "krdc" client, 
which can scale virtual machines to be really small for when you're not using 
them and also has a decent fullscreen mode.

Here's a screenshot of krdc's scaling capabilities:

Note several Linux distros running in both console mode and graphical.  Some 
of the VMs are paravirt, others (see the Windows guest in the upper right) 
are fully virt.

> Also, I have the 
> Vanderpool Technology activated in the bios, fyi.  Also, can I have a
> virtual os of windows xp?

Yes, if you have VT activated you should be able to install a Windows XP Os in 
a full virt virtual machine.

> Like where it had asked me about the 
> installation media, if I had provided windows xp media, would it have
> worked?

Yes, *if* you use full virtualisation.  It won't work with paravirt.

> Also, how do I tie a linux install dvd to nfs?  I know that in 
> order to do this, I need to find out where my dvd is mounted.  How do I
> find that out?  I've been going to /dev and searching there, how do I know
> which one is for my dvd player? Would it be /dev/dr0/ /dev/sdc?  Anyhow,
> thanks.

It varies.  Many distros will make it available as /dev/dvd.

> I've been retrying the virtual os installation and a blue screen comes up
> and asks me to put in the web server and fedora directory.  I've been using
> http://fedora.tu-chemnitz.de/pub/linux/fedora/linux/releases/7/Fedora/i386/
>os/, but I guess I need another one.  Any of you guys have any media http
> links to Fedora 7 or 8?

This page: http://www.mail-archive.com/fedora-xen%40redhat.com/msg00344.html
suggests that your URL is of the right form.  What errors did you see?  Was 
there a reported error message?  If it just pauses for a while it might just 
be accessing the install media URL and downloading an install image (which 
might take a little while, depending on your network speed).


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