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In my day-job all our Linux boxes (bar 3) are Xen VMs. I wanted a way to take a backup of these with out the risk of the files changing underneath. For performance reasons I am running all of them on Logical Volumes. Within these VMs the DomU OS is once again using LVM for various reasons. This does create some headaches for taking the backup.

There's a bug in virt-install and virt-manager on Ubuntu 8.10 that does not let you run Windows XP as a guest under KVM. During the Windows installation, the guest needs to be rebooted, and then you get the following error, and Windows XP refuses to boot: "A disk read error occured. Press Ctrl+Alt+Del to restart". This guide shows how you can solve the problem and install Windows XP as a KVM guest on Ubuntu 8.10.

This article shows how you can install the PowerDNS nameserver (with MySQL backend) and the Poweradmin control panel for PowerDNS on a Fedora 10 system. PowerDNS is a high-performance, authoritative-only nameserver - in the setup described here it will read the DNS records from a MySQL database (similar to MyDNS), although other backends such as PostgreSQL are supported as well. Poweradmin is a web-based control panel for PowerDNS.

This tutorial provides step-by-step instructions on how to install Xen 3.3.1 on a Debian Etch (4.0) system. Xen lets you create guest operating systems (*nix operating systems like Linux and FreeBSD), so called "virtual machines" or domUs, under a host operating system (dom0). Using Xen you can separate your applications into different virtual machines that are totally independent from each other (e.g. a virtual machine for a mail server, a virtual machine for a high-traffic web site, another virtual machine that serves your customers' web sites, a virtual machine for DNS, etc.), but still use the same hardware.

In the past I was trying many different linux distros. Each has its own package management systems: debian has apt, mandrake has urpmi, yellowdog has an apt front-end for rpm, suse has yast... While they all are quite similar and not difficult to use, I found that I often made mistakes because I often forgot which system I was using and the exact commands on that system. Another issue is that I wish I could keep track how I installed/removed those packages. So I wrote a simple wrapper for various package management systems.

Virt-Manager (Virtual Machine Manager) is a graphical interface for managing KVM and Xen guests on the local and also on remote systems. You can use it to start, stop, pause, create, and delete guests, and you can connect to the guests using the graphical console. This guide shows how you can use it to manage KVM guests on an Ubuntu 8.10 desktop.

This tutorial describes how you can install Apache2 with mod_fcgid and PHP5 on CentOS 5.2. mod_fcgid is a compatible alternative to the older mod_fastcgi. It lets you execute PHP scripts with the permissions of their owners instead of the Apache user.

This tutorial provides step-by-step instructions on how to install Xen on a Debian Lenny (5.0) system (AMD64). Xen lets you create guest operating systems (*nix operating systems like Linux and FreeBSD), so called "virtual machines" or domUs, under a host operating system (dom0). Using Xen you can separate your applications into different virtual machines that are totally independent from each other (e.g. a virtual machine for a mail server, a virtual machine for a high-traffic web site, another virtual machine that serves your customers' web sites, a virtual machine for DNS, etc.), but still use the same hardware. This saves money, and what is even more important, it's more secure. If the virtual machine of your DNS server gets hacked, it has no effect on your other virtual machines. Plus, you can move virtual machines from one Xen server to the next one.

This tutorial shows how you can mirror your web site from your main web server to a backup server (both running Fedora 10) that can take over if the main server fails. We use the tool rsync for this, and we make it run through a cron job that checks every x minutes if there is something to update on the mirror. Thus your backup server should usually be up to date if it has to take over.

HyperVM is a multi-platform, multi-tiered, multi-server, multi-virtualization web based application that will allow you to create and manage different virtual machines each based on different technologies across machines and platforms. Currently it supports OpenVZ and Xen virtualization and is available for RHEL 4/5 as well as CentOS 4 and CentOS 5. This tutorial shows how to install it on a CentOS 5.2 server to control OpenVZ containers. I will also explain how to manage OpenVZ containers with HyperVM on a remote CentOS 5.2 server ("slave").

There are various reasons to set up quick "sandbox" instances of MySQL. You can use them to test different types of replication (such as master-master or various slave topologies), to test your code against different versions of MySQL, or to setup instances of MySQL on a per developer basis where each person has their own database running on a different port so they can breakdown/setup the DB easily or make schema changes without affecting other team members. A perfect tool to do all of these things easily is MySQL Sandbox.

This tutorial describes how you can install Apache2 with mod_fcgid and PHP5 on Debian Etch. mod_fcgid is a compatible alternative to the older mod_fastcgi. It lets you execute PHP scripts with the permissions of their owners instead of the Apache user.

This guide shows how you can create USB startup disks (on your USB flash drive) from various Linux distributions with UNetbootin. This is useful if you want to install a Linux distribution on a computer that has no CD/DVD drive.

This document describes how to install a Postfix mail server that is based on virtual users and domains, i.e. users and domains that are in a MySQL database. I'll also demonstrate the installation and configuration of Courier (Courier-POP3, Courier-IMAP), so that Courier can authenticate against the same MySQL database Postfix uses. The resulting Postfix server is capable of SMTP-AUTH and TLS and quota (quota is not built into Postfix by default, I'll show how to patch your Postfix appropriately). Passwords are stored in encrypted form in the database (most documents I found were dealing with plain text passwords which is a security risk). In addition to that, this tutorial covers the installation of Amavisd, SpamAssassin and ClamAV so that emails will be scanned for spam and viruses. I will also show how to install SquirrelMail as a webmail interface so that users can read and send emails and change their passwords.

This article shows how you can install the PowerDNS nameserver (with MySQL backend) and the Poweradmin control panel for PowerDNS on an Ubuntu 8.10 system. PowerDNS is a high-performance, authoritative-only nameserver - in the setup described here it will read the DNS records from a MySQL database (similar to MyDNS), although other backends such as PostgreSQL are supported as well. Poweradmin is a web-based control panel for PowerDNS.

This document describes how to install a PureFTPd server that uses virtual users from a MySQL database instead of real system users. This is much more performant and allows to have thousands of ftp users on a single machine. In addition to that I will show the use of quota and upload/download bandwidth limits with this setup. Passwords will be stored encrypted as MD5 strings in the database.

The Sony PlayStation 3 is a DLNA compatible device, DLNA is a framework where home electronics can share digital media and content seamlessly. This tutorial is a followup to the previous howto on Ubuntu. Given that I like most others use CentOS as their server distribution of choice, I find it fitting to run my DLNA server on it as well. Although several other open source media servers exist, I chose to use Fuppes due to its ease of use as well as built in support for transcoding.

This article explains how you can cache your web site contents with Apache's mod_cache on Debian Etch. If you have a high-traffic dynamic web site that generates lots of database queries on each request, you can decrease the server load dramatically by caching your content for a few minutes or more (that depends on how often you update your content).

This guide shows how you can install Ubuntu 8.10 on a USB flash drive. Ubuntu 8.10 comes with a tool that lets you create a USB startup disk easily - this startup disk behaves like the Ubuntu 8.10 Live-CD. This is useful if you want to install Ubuntu on a computer that has no CD/DVD drive. When you create the USB startup disk, you can also specify that you want your USB system to be persistent between boots (i.e., it does not lose your settings, documents, etc.) - that way you get a fully usable OS that you can carry around in your pocket.

This how to will allow you to configure a Postfix mail server with virtual hosting. Virtual hosting means that you can add as many maildomains as you want and subsequentially as many mailboxes for these domains as you want. Here we we use an LDAP backend for both the MTA (Postfix) and POP3/IMAP server (Dovecot), and a web based management interface.