Category: Virtualisation

Virtualisation and cloud computing

Installing a Red Hat based DomU on a Debian Dom0

The first step is to copy /images/xen/vmlinuz and /images/xen/initrd.img from the Fedora (or RHEL or CentOS) DVD somewhere convenient, I use /boot/OS/ (where OS is the name of the image) but other locations will do. Now choose a suitable Ethernet MAC address for the interface (see my previous post on how I choose them [1]). […]


Xen and Swap

The way Xen works is that the RAM used by a virtual machine is not swappable, so the only swapping that happens is to the swap device used by the virtual machine. I wondered whether I could improve swap performance by using a tmpfs for that swap space. The idea is that as only one […]

Benchmark Virtualisation

The Future of Xen

I’m currently in Xen hell. My Thinkpad (which I won’t replace any time soon) has a Pentium-M CPU without PAE support. I think that Debian might re-introduce Xen support for CPUs without PAE in Lenny, but at the moment I have the choice of running without Xen or running an ancient kernel on my laptop. […]


Xen for Training

I’m setting up a training environment based on Xen. The configuration will probably be of use to some people so I’m including it below the fold. Please let me know if you have any ideas for improvements. The interface for the user has the following documentation: sudo -u root xen-manage create centos|debian [permissive] Create an […]

Security Virtualisation

Xen and Security

I have previously posted about the difference between using a chroot and using SE Linux [1]. Theo de Raadt claims that virtualisation does not provide security benefits [2] based on the idea that the Xen hypervisor may have security related bugs. From my understanding of Xen a successful exploit of a Xen system with a […]

Security Virtualisation

Xen Memory Use and Zope

I am currently considering what to do regarding a Zope server that I have converted to Xen. To best manage the servers I want to split the Zope instances into different DomU’s based on organisational boundaries. One reason for doing this is so that each sys-admin will only be granted access to the Zope instance […]


Context of /dev/xvc0

I have just converted a Fedora Core 5 server to a CentOS 5 Xen Dom0 with Fedora Core 5 as a DomU. The process took a little longer than expected because I didn’t have console or network access to the DomU initially. It turned out that /etc/modprobe.conf was configured to have the tg3 device for […]

Security Virtualisation

Duplicating a Xen DomU

A fairly common request is to be able to duplicate a Xen instance. For example you might have a DomU for the purpose of running WordPress and want another DomU to run MediaWiki. The difference in configuration between two DomU’s for running web based services that are written in PHP and talking to a MySQL […]


Out Of Memory Errors and Apache

I’ve been having problems with one of my Xen virtual servers crashing with kernel error messages regarding OOM conditions. One thing I had been meaning to do is to determine how to make a core dump of a Xen domain and then get data such as the process list from it. But tonight I ended […]

unix-tips Virtualisation

Identifying the Distribution of a Linux System

I just needed to test something so I mounted the filesystem of one of my Xen domains in the Dom0 and chroot’d into it (I didn’t need the overhead of running a DomU for a quick test). Then strangely I found that my chroot environment had no apt-get and no dpkg installed. After a small […]