Xen

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Revision as of 14:30, 7 October 2008 by Pert (talk | contribs) (Big changes for wotan.)
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Overview

  • We currently have a single Xen host: WOTAN. It replaced the previous Xen hosts as it has more of everything (disks, CPUs, RAM, PSUs).
  • We run i386 Xen 3.0.3 with PAE (as packaged in Debian etch).
  • We use LVM to create volumes for each domU's root and swap partitions.
  • We have a homebrew script to create the LV and use debootstrap to install the OS.

How to Add New Instances

The VM creation script gets the new system's IP address from DNS so the first job is to see the DNS_Service page for details on how to set up a new entry for your system.

Login to wotan, which is the main xen machine. Use the mkdomU.bash script to create the new instance like so:

mkdomU.bash -vh <newmachinename>

Say yes to shadow passwords, type in root password (twice), say no to creating a user account.

If you want to do something complicated, have a look at /etc/mkdomU.conf, or at the script at /usr/local/bin/mkdomU.bash .

Don't forget to unmount the domU filesystem!

umount /mnt/mkdomU

Run

xm create -c <newmachinename>.conf

to get the instance up and running. You should be able to log in. Use ctrl+] to get back to vislor's console.

Booting and Shutting Down

Xen's init scripts are set up to perform an `xm save` (copy the RAM to disk) for each domU that's running when vislor and/or adric are shut down and to restore saved domUs on boot. This should take care of the cases where tardis is shut down intentionally, but a bit more work will have to be done following an unexpected power loss. (When do they happen anyway? ;-)

To start all domUs on vislor do:

for foo in /etc/xen/*.conf; do xm create -c $foo; done
<WAIT FOR A LOGIN PROMPT>
ctrl+]
<WAIT FOR A LOGIN PROMPT>
ctrl+]
....