Running on Bad Memory

Being able to rely on your memory is one of the most important aspects of having a stable PC. Thus, paying extra for premium memory seemed like a wise choice to me.

Yet I have been surprisingly unlucky with my memory.

In this post I’ll show how to identify broken memory cells and how to prevent Windows and Linux from accessing them, resulting in a stable system while discarding only a few Kilobytes of memory.

Read More

Thread-Safe Random Access to Zip Archives

Many games choose to store their resources in packages instead of shipping the potentially thousands of individual files directly. This is sometimes an attempt at tamper-proofing, but mostly it is about performance. Try copying a thousand 1 KiB files from one drive to another, then copy a single 1 MiB file on the same way – the former operation will take many times longer.

A good choice for a package format is the well known .zip archive. It’s not necessarily well-designed, but it decompresses fast and you definitely won’t have any problems finding tools to create, modify and extract .zip archives. Thus, when I started work on a file system abstraction layer for my future games, seamless .zip support was one of my main goals (I may also add 7-Zip at a later time just for fun).

Here is the design I came up with after exploring the file system APIs available on Windows, WinRT and Linux:

UML diagram showing the design of my file system abstraction layer

You may notice some rather radical design choices in my File class: there are no Open() or Close() methods and there is no Seek() method, either – each read or write specifies the absolute position without requiring the file to be opened.

Read More

VirtualBox on Headless Gentoo

Being an adherent of Continuous Integration, I need a build machine that runs round the clock even when my workstation is turned off. As I’m running a small home server, this wouldn’t be an issue — if it weren’t for the fact that my home server runs Linux and 99% of my development happens in Windows. So I use virtualization to run a small Windows system on top of my home server.

In the past I used VMware for this job. VMware worked well for me and performance was quite good, but now that I’ve switched to a fully headless system, I noticed that the vmware-server package pulls in most of the X11 libraries – which I’m not particularly keen on having on my system due to their compile times.

A cube mounted like a display showing the Sun logo

So I went shopping for some alternatives. KVM sounded interesting (and was the leanest virtualization solution I could find), but the Gentoo Wiki stated that Windows didn’t work in qemu with recent kernels, so I went looking on – and found VirtualBox. This article explains how to set up VirtualBox on a headless Gentoo system.

Read More

Installing TeamCity on Gentoo Linux

If you haven’t heard of Continuous Integration yet, it’s the practice of setting up an automated system that rebuilds projects automatically whenever someone commits a new change to your source code repository. It ensures that whatever is in your repository builds and runs: automated builds usually involve compiling, running unit tests and packaging the installer.

Official TeamCity logo depicting a blue T and orange C

To do continuous integration, you need a tool that monitors your source code repository and starts the builds – a continuous integration server. My weapon of choice is TeamCity, a free CI server written in Java with first-class support for .NET and its toolchain (like NAnt, NUnit, NCover or PartCover).

TeamCity is pretty easy to deploy – the Windows package has an installer which leaves you with a fully working server after just a few clicks and even the Linux package is pretty simple to deploy: Download, unzip, run and you’re done. To properly integrate it into a Linux server (so it will come back up after rebooting and can be reached via HTTP without having to run either Apache or TeamCity on a non-standard port), you’ll need to run your own Tomcat server.

This guide will tell you how to do it!

Read More

Integrating SpamAssassin into Courier

Please excuse the current flurry of Linux articles. I’m moving servers and this is my way of writing notes to myself and possibly helping out others. Normal service will resume shortly ;-)

This article is a follow-up to my guide on Installing Courier on Gentoo. As long as you have a working Courier installation on your system, there should be no issues following this guide.

Drawing of an arrow piercing through a stack of mail envelopes

Running a mail server without some kind of spam filtering is just insane these days. SpamAssassin is a nice solution, especially if you run SpamAssassin during the SMTP transaction to reject spam while it is being uploaded to your server.

Read More

Installing Courier on Gentoo

On my previous system, I had used qmail (netqmail actually, which is qmail with some patches). Qmail is moderately difficult to set up and in its 3 years lifespan on my system, it has broken down on several occasions. That’s why I decided to use another mail server when I moved my domains to a different system.

Because the Courier IMAP server has never let me down before, I decided to give the Courier Mail Server a chance. Lots of people are using Courier IMAP to access their mail but Exim, Postfix or Qmail to accept incoming emails. Even the Gentoo Wiki contains various HowTos for these combinations, but not a single one for a homogenous Courier setup. After trying out Courier, I don’t see why, so this is my attempt to rectify the situation (and to remember what needs to be done for the next time I’m moving my domains to another system!)

Read More

Installing wTorrent on Gentoo

If you want to download torrents on your Linux system, there are several clients to choose from. One of the nicest and fastest clients is rTorrent. It is full-featured, supports encryption, dynamic host table exchange and achieves fantastic download speeds.

But its best feature probably is that it isn’t bound to any windowing toolkit. You can install one of its GUI frontends to manage it on your fancy KDE 4 desktop machine, but you can also run it on a headless system and manage torrent from a text-only console. And if you happen to run it on a home server like me, there’s wTorrent, a beaufitful AJAX-driven web frontend that allows you to manage your torrents in your browser.

Screenshot of the wTorrent web frontend for rTorrent

Installing wTorrent isn’t the easiest thing to do, so, as when I tried to get the best out of my SSD, I decided to write this small article explaining how to do it. I’m using Gentoo Linux, but it shouldn’t be too hard to apply this article to another Linux distribution.

Read More

Aligning an SSD on Linux

I’ve got a small home server with a software RAID-5 for storing my files. It also runs a few virtual machines and acts as a NAT router for internet access. Nothing expensive, just some Frankensteinian patchwork built from old hardware left over when I upgraded my workstation. Nevertheless, I granted it a brand new Intel X25-M SSD last week.

Photo of an Intel X25-M SSD drive, which is a metal box smaller than a CD case

Did I mention that this server is running Gentoo Linux? I thought this would be a good time to do a fresh install and get everything right that might have gone wrong the first time. Besides, installing Linux always is an interesting (and masochistic) experience, especially when your chosen distribution has no installer :)

Because getting my partitions and file systems aligned also proved to be difficult task, I thought why not make a small article out of this!

Read More