Posts Tagged ‘PV’

SolusVM displaying wrong disk usage statistics for Xen PV VMs

Sunday, December 29th, 2013

Recently some of our Xen PV VMs started to show strange disk space usage statistics in SolusVM – despite there being plenty of space left on the disk in the VM, SolusVM was reporting that the disk was nearly full!

I struggled to find any public information about this, but apparently it is a known problem with SolusVM and the version of the “df” utility used in RHEL/CentOS 6.5. There have been some slight changes to the way that df displays its output and this causes SolusVM to interpret the disk usage figures incorrectly.

SolusLabs have posted a workaround for this at http://bin.soluslabs.com/1083/38662948/raw/ and I’m reproducing it here for posterity as well as in the hope that it will get indexed:

Fix for Xen PV disk usage showing 100% when using a CentOS 6.5 host node
========================================================

The “df” output in CentOS 6.5 has changed. You may notice this when you upgrade you’re host node from CentOS 6.4. All the Xen PV virtual servers will show 100% disk space used.

On the affected host node edit /usr/local/solusvm/data/advanced.conf and add the following line:

XENFIXCENTOS6DF=”1″

Then run these commands:

wget https://www.dropbox.com/s/j8nu3ye09x9ehwq/command.php -O /usr/local/solusvm/www/command.php
wget https://www.dropbox.com/s/93hsnzzmpwny3r4/solusvmc-xen -O /usr/local/solusvm/core/solusvmc-xen
chmod 6777 /usr/local/solusvm/core/solusvmc-xen

Now when you reboot a virtual server (with the reboot button) the disk usage should update correctly.

Citrix XenServer boot from CD/DVD

Sunday, September 8th, 2013

If you’re using Paravirtualised (PV) guest Virtual Machines on Citrix XenServer, then it’s not immediately obvious how to boot the guest from a CD/DVD should you need to. In the “Boot Options” tab of the Properties for the Virtual Machine, the “Boot Device” drop down menu will be greyed out, with no obvious way of enabling it.

The actual method of booting a Virtual Machine from a CD/DVD is a little less obvious – go to the Virtual Machine in question, switch to the console tab and select the CD/DVD from the drop down list at the top. Make sure that the Virtual Machine is shutdown, then click on the “VM” menu, then “Start/Shut down” and select “Start in Recovery Mode”. The Virtual Machine will now boot from whichever CD/DVD you’ve selected.