Linux

This is now on the wiki.

On my spare time, I manage a handful of servers. And even if it’s not really my job, I try to do it well and efficiently. All of them work on Debian because it’s simple to manage. I started using cron-apt a few years ago. I started by upgrading everything automatically, this was a big mistake. I switched to only sending mails on available upgrades and doing the upgrade manually. But this is also quite painful because 95% of the time, it consists in typing “apt-get dist-upgrade -y” and waiting and I have lots more interestings things to do. ...

I’ve been testing btrfs for some months now. One of the most interesting features of this file-system is its snapshoting capabilities. Before that I was using rsnapshot. The issue with rsnapshot is that its lowest atomic level for snapshotting is the files themselves using hard-links. So any database table where one row is changed is copied completely. Btrfs as you might guess will only copy the modified chunks (I don’t know the atomicity of them [but who cares?]). ...

Debian released a new version of their system. I updated it on the server that powers this blog, it took me something like one hour to do the whole system upgrade. There was only a little glitch with mysql’s my.cnf file that had an unsupported “skip-bdb” line. Everything else went fine… The very good thing in this new release is the new kfreebsd version (available in i386 and x86_64). It brings the power of the FreeBSD kernel to the great Debian OS. If you don’t see the point, read this. To put in a nutshell: a more stable kernel with less legal issues, better vendors support and the same softwares. ...

XRDP is a very interesting project. It allows to create a terminal server on Linux hosts using the RDP protocol. I think the RDP protocol is a great protocol (better than VNC) but that’s not why I’m writing this. The important thing about this tool is: It’s freaking simple to use. On Debian, just type: apt-get install xrdp -y On Red Hat Enterprise Linux, just type: yum install xrdp Then, you have to start it: ...

I often hear people talking about which technology is better between C / C++ / C# .Net / java. Most of the time, it’s more a political/brotherhood/community thing (like football, even thought frenchies like me aren’t so proud of their team now) than a technical talk. I find it absurd. Computer science is about efficiency and making more money. You can take into account the pleasure you have to work on a technology (as you will be more likely to be more efficient with it), but it should still remain about efficiency. ...

I find the concept of prioritization very interesting. It just enables you to do more with less. Doesn’t that sound great ? Let’s say you want to be able to respond to user requests as fast as possible but update your data in a low priority manner : You can set the process CPU priority from -20 (high priority) to 19 (low priority) by using the command : nice -n <priority> <command> You can set the process IO priority in 4 classes (0: none, 1: realtime, 2: best-effort, 3: idle) with some priorities within these classes (0-7, lower being higher prio). But you have to enable the CFQ (Complete Fair Queueing) scheduler first by typing something like that : ...

I found out that there is real test than the little one I did here. The core of the post is this spreadsheet : I recently did a basic comparison test between C++ (g++) and C# .Net (mono). My point is to show that the .Net framework has performances close to the C++ ones. It allows automatic hardware-specific optimization. The only real drawback you have in the .Net framework is the garbage collector. It prevents the C# .Net it from being a realtime language/framework. But does it really matter for you ? ...

Sometimes, you just need to redirect a port on Linux. The solution I could find is to add an entry into xinetd. Here is a sample /etc/xinetd.d file I have, it just redirects the 587 (tcp) port to the 993 port of gmail’s servers. I have to do this because Virgin Mobile France blocks the 993 tcp port. If you’re in the same situation, you can use my server to access you gmail IMAP access. You just have to set the server name to “webingenia.com” and the port to “587”. ...

I talked about this earlier. The mono tools for Visual Studio is a commercial product that easily enables you to test and port your Windows applications to mono. As I told before this is really a great idea. Because I think Visual Studio is the best IDE and Linux is the best server OS (in my opinion, it’s more efficient and more robust than Windows Server). So, I think it’s the perfect gateway between this two very different (but very close since Mono appeared) environments to achieve greatness. ...