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convert mysql table from MyISAM to InnoDB
30/12/2009 | mad mad mod

MyISAM is the default storage engine for MySQL. Unfortunately it doesn't support transactions or foreign keys (but it has some other nice features like compression). However, because InnoDB does su [ ... ]

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Hello World in Fortran
29/12/2009 | mad mad mod

This article describes how to write, compile and execute a "Hello World" program in Fortran on Linux (RedHat / Centos / Fedora). 1. the prerequisitesa text editor of your choice (e.g. vi)a Fortr [ ... ]

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The Basics

XEN uses 2 different native configuration file formats. The "old" one is S-expressions (sexp) which is usualy used for configuration files in /var/lib/xend/. The default file ending is ".exp". If you want to know more about Symbolic Expressions you might want to take a look at http://en.wikipedia.org/wiki/S-Expression

The "newer" one is used for files in /etc/xen and has a Python like syntax (sorry I dont know the name). If you check the /usr/sbin/xm file you will see that it is a python script and I guess thats why you can also use the Python format.

Which one should I use now?

I would use neither of the two! Instead, I would use pure xml for DomU configuration files. Because XEN does not understand XML you have to use libvirt.

What is libvirt?

The following text is from the libvirt.org website:

libvirt is:

* A toolkit to interact with the virtualization capabilities of recent versions of Linux (and other OSes).
* Free software available under the GNU Lesser General Public License.
* A long term stable C API
* A set of bindings for common languages
* A CIM provider for the DMTF virtualization schema
* A QMF agent for the AMQP/QPid messaging system

libvirt supports:

* The Xen hypervisor on Linux and Solaris hosts.
* The QEMU emulator
* The KVM Linux hypervisor
* The LXC Linux container system
* The OpenVZ Linux container system
* The User Mode Linux paravirtualized kernel
* The VirtualBox hypervisor
* Storage on IDE/SCSI/USB disks, FibreChannel, LVM, iSCSI, NFS and filesystems

libvirt provides:

* Remote management using TLS encryption and x509 certificates
* Remote management authenticating with Kerberos and SASL
* Local access control using PolicyKit
* Zero-conf discovery using Avahi multicast-DNS
* Management of virtual machines, virtual networks and storage
* Portable client API for Linux, Solaris and Windows

There are several utilities available to manage virtual machines and libvirt. I think on RedHat / Fedora based systems the "virsh" utility is something like the standard tool to manage virtual machines with libvirt. If you are familiar with "xm" then it should be easy to get used to virsh.

There is a nice documentation about the XML configuration files here: http://libvirt.org/format.html

How does it work now?

Depending on how you have installed your virtual machine, you will not have an XML file now. If you want to have such a file from a defined virtual machine you can run