this is obsolete doc -- see http://doc.nethence.com/ instead

XEN usage and tweaks 

Custom XEN guest wrappers 

Install custom XEN guest wrappers, 

cd ~/

mkdir -p bin

cd bin

wget http://pbraun.nethence.com/code/sysutils_xen/...

wget http://pbraun.nethence.com/code/sysutils_xen/...

wget http://pbraun.nethence.com/code/sysutils_xen/...

#for f in `ls -1 ~/code/sysutils_xen/`; do

#        ln -s ~/code/sysutils_xen/$f

#done

Making a guest template or backup 

Remove the SSH keys from the guest, 

rm -f /etc/ssh/*key*

ll /etc/ssh/

Tar up the guest, 

tar czSf centos5x32.tar.gz centos5x32

Note. -S, --sparse for sparse file virtual disk 

Then extract it elsewhere and use the following clone procedure, but use 'mv' instead of 'cp'. 

Cloning / renaming a guest 

Make sure the source guest is shut down and proceed, 

cd /data/guests/

cp -R centos5x32 newguest

#mv centos5x32 newguest

cd newguest

sed 's/centos5x32/newguest/g;

  s/ip=[^,]*,/ip=192.168.11.12,/;

  s/vifname=[a-z0-9]*/vifname=vnewguest_0/;

  ' centos5x32 > newguest

rm -f centos5x32

mv centos5x32.disk newguest.disk

Note. 'cp' is sparse capable by default 

You can then start the guest and change its network configuration. 

Launch guests at boot time 

Enable guests at boot time, 

cd /etc/xen/auto/

ln -s /data/guests/guestX/guestX

Troubblshooting 

When starting a domU, if you get this error msg while "/kern" is mounted, 

Error: [Errno 2] No such file or directory: '/kern/xen/balloon'

It means there's not enough memory left for the guest. 

When starting a domU, if you get this error msg, 

Error: (22, 'Invalid argument')

the dom0 and domU kernels don't match (PAE vs. non-PAE). 

If you get this error when trying to launch a guest, 

xc_dom_boot_mem_init: can't allocate low memory for domain

just make sure the guest architecture is supported by the dom0 :-) (e.g. a x86_64 guest might not be supported on x86 host) 

Hot migration 

Once your XEN farm is configured (IP settings and shared disk filesystem), edit the configuration, 

vi xend-config.sxp

like, 

(xend-http-server yes)

(xend-relocation-server yes)

(xend-port            8000)

(xend-relocation-port 8002)

(xend-relocation-address '')

### (xend-relocation-hosts-allow '')  

Basic dom0 management 

On RHEL5 there's a graphical interface, 

virt-manager

Note. press "Ctrl" to release the mouse from the guest console 

Back to the terminal, list the currently started virtual machines, 

xm list

Note. dom0 is the base system, not a VM. 

Start a vm, 

xm create path/to/vmconfig

to get its console immediately, 

xm create path/to/vmconfig -c

or once the VM is started, you can get the console afterwards, 

xm console vmname

To exit from the console, 

ctrl-altgr-] (something like that)

Besides, it's very convenient to use VM consoles inside a screen session, having a different VM console on each screen window. It's possible to kill the console simply by killing the screen window, 

^A k

GNU Screen configuration : http://pbraun.nethence.com/doc/misc/screen.html 

To stop a VM, 

xm shutdown vmname

Note "xm destroy" will act the same as an immediate poweroff, while "xm sh" should tell the system to shutdown properly. Check wheter it behaves correctly within both, HVM and paravirtualized guests. 

Note. it's possible to use shortcuts. Instead of the full xm commande, do 

xm cr <vmname>  # create

xm co <vmname>  # console

xm sh <vmname>  # shutdown

xm de <vmname>  # destroy

xm li      # list

Advanced dom0 management 

Detailed information, 

xm list -ll

xm info

See what's going on, 

xm vcpu-list

xm tmem-list

xm network-list

Set dom0's allocated memory dynamically, 

xm mem-set 0 512M

References 

RHEL Kernel Performance Optimization and Characterization and Tuning : http://people.redhat.com/dshaks/Larry_Shak_Perf_Summit08.pdf 

Xen Disk I/O Benchmarking: NetBSD dom0 vs Linux dom0 : http://users.piuha.net/martti/comp/xendom0/xendom0.html 

Xen Virtualization on Linux and Solaris : http://bderzhavets.blogspot.com/ 

XEN: Install SLES 9 SP3 domU on SLES 10 XEN dom0 : http://www.novell.com/coolsolutions/feature/18236.html 

Xen DomU Linux Installer Creation : http://emmeff.blogspot.com/2006/07/howto-install-opensuse-10.html 

Virtualization in Fedora 8 : http://fedoraproject.org/wiki/Docs/Fedora8VirtQuickStart 

Xen3 on CentOS4 : http://www.karan.org/blog/index.php/2005/12/06/xen3_on_centos4 

Xen, Virtualization on Linux : http://www.redhat.com/magazine/004feb05/features/virtualization/ 

(FR) Virtualisation avec Xen : http://www.bortzmeyer.org/xen.html 

Management tools 

Virt-manager : http://virt-manager.et.redhat.com/ 

Convirt GUI : http://xenman.sourceforge.net/ 

virsh : http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/Virtualization-en-US/ch-virt-task-virsh.html 

Enoalism GUI : http://www.enomalism.com/ 

Clobber : http://cobbler.et.redhat.com/