Installing in a HVM with CD and then converting it to PV.

There's some info here:

http://markmail.org/message/ib5bctd3amqqzl5u#query:convert%20hvm%20xen%20to%20paravirtual%20initrd+page:1+mid:pg3g44k5cdmuyqes+state:results
http://old.nabble.com/Converting-full-virtualized-Linux-domUs-to-use-paravirtualized-drivers-td18942359.html

To install a Xen Guest Os from the first time, you need to:

Create the Filesystems for it on the Xen Host:

vgdisplay
lvcreate -L 12G -n ui64_root vg_root
lvcreate -L 4G -n ui64_swap vg_root
lvdisplay

Create the Xen config file for the machine in /etc/xen/ui64 with this content:

name = "ui64"

vcpus = 2
memory = 2048
disk = ['phy:/dev/vg_root/ui64_root,hda,w',
        'file:/root/SL.54.110309.DVD.x86_64.disc1.iso,hdc:cdrom,r',
        'phy:/dev/vg_root/ui64_swap,hdb,w']
vif = ['mac=00:16:3E:64:00:64,bridge=xenbr0']

builder = "hvm"
kernel = "/usr/lib/xen/boot/hvmloader"
device_model = "/usr/lib64/xen/bin/qemu-dm"
pae = 1
boot = "cd"
vnc = 1
vncviewer = 1
vncdisplay = 7

Start the virtual machine and open the vnc console:
```
xm create ui64
vncviewer localhost:7
```
Perform the installation:
- The least software installed the better
- make sure you install virtualization
- Configure networking manually.
- If you need to change disk, perform: xm block-configure [Dom-ID] file:/scratch/SL.56.061711.DVD.x86_64.disc2.iso hdc:cdrom r
- confirm reboot. Then shut down the machine with xm destroy ui64
Upon restart remove all unnecesary services from bootup, and edit the /etc/modprobe.conf file to be like this. After a kernel reinstallation (or running mkinitrd manually) the initrd image will be able to boot from paravirtualized devices:
```
alias eth0 xennet
alias scsi_hostadapter xenblk 
```

Finally install the xen kernel, which should be on the cdrom (mount it first) and uninstall the non-xen one.

mount /dev/hdc /mnt
rpm -i /mnt/SL/kernel-xen-2.6.18-164.2.1.el5.x86_64.rpm
rpm -i /mnt/SL/kernel-xen-devel-2.6.18-164.2.1.el5.x86_64.rpm
rpm -e kernel-devel-2.6.18-164.2.1.el5.x86_64 kernel-2.6.18-164.2.1.el5.x86_64
cat /boot/grub/menu.lst

Then check the xen kernel is the default to be loaded on boot, and halt the VM.

Before starting it again, replace the /etc/xen/ui64 xen config file to match this content (to be para-virtualized):

name = "ui64"

vcpus = 2
memory = 2048
disk = ['phy:/dev/vg_root/ui64_root,hda,w',
        'phy:/dev/vg_root/ui64_swap,hdb,w']
vif = ['mac=00:16:3E:64:00:64,bridge=xenbr0']

bootloader = "/usr/bin/pygrub"
on_reboot = 'restart'
on_crash = 'destroy'
extra = "xencons=tty"

Boot up (with console) and change the boot parameters in grub (for the xen kernel) so that it contains the root(hd0,0), a kernel line and an initrd line. If the boot is ok, change it definately in /boot/grub/menu.lst. If it doesn't boot then you can always go back to full virtual and fix whatever needed.
Backup the basic installation if wanted. From the Xen Host perform
```
dd if=/dev/vg_root/ui64_root of=/root/ui64_root.img
```
After the first backup, it's a good idea to install the software needed (or most likely needed) in all machines that it's going to be replicated to. This is a suggestion:
- Disable selinux

Installing in a PV (para-virtualized) machine

OBSOLETE, DOESN'T WORK because it doesn't install a kernel... maybe using kickstart could do

To install a Xen Guest Os from the first time, you need to:

Create the Filesystems for it on the Xen Host:

vgdisplay
lvcreate -L 12G -n ui64_root vg_root
lvcreate -L 4G -n ui64_swap vg_root
lvdisplay

Create the Xen config file for the machine in /etc/xen/ui64 with this content:

name = "ui64"

vcpus = 2
memory = 2048
disk = ['phy:/dev/vg_root/ui64_root,xvda,w',
        'phy:/dev/vg_root/ui64_swap,xvdb,w']
vif = ['mac=00:16:3E:64:00:64,bridge=xenbr0']

kernel = '/root/xenkernel/sl54_64/vmlinuz'
ramdisk = '/root/xenkernel/sl54_64/initrd.img'
on_reboot = 'destroy'
on_crash = 'destroy'

Make sure there exists both vmlinuz and initrd.img from above in the Xen Host. They come from the /images/xen directory on the SL54 first CD, or in the repo.
Start the virtual machine and open the vnc console: xm create -c ui64
The xen console will come up, just make a normal installation as desired. Network is left to be configured with dhcp. You may also want to use a local repository or the one at ftp://mirror.switch.ch/mirror/scientificlinux/54/x86_64/

After installation the machine will halt. To go on we need to replace the old /etc/xen/ui64 with this new one:

name = "ui64"

vcpus = 2
memory = 2048
disk = ['phy:/dev/vg_root/ui64_root,xvda,w',
        'phy:/dev/vg_root/ui64_swap,xvdb,w']
vif = ['mac=00:16:3E:64:00:64,bridge=xenbr0']

bootloader = "/usr/bin/pygrub"