Category Archives: Linux

The problem with excessive buffering in networks

I have been shaping the traffic going to and from my Linux server at home, which doubles as an Internet router, for a couple of years now to avoid the serious implications a congested network can have on interactive sessions, such as games and SSH sessions.

This morning I read an interesting article on the subject by Jim Gettys, and the problem seems to be worse than anticipated. You can read more about the problem here, and the detailed analysis here.

Google Reader Android app

The official Google Reader application for Anrdoid is finally here. For me, this is really good news, since I have been hesitant to install applications such as NewsRob for security reasons.

Yet another Android security vulnerability

Android security holes seem to be pouring down from the skies nowadays. This new vulnerability allows a malicious website to access files located on your SD card.

For more details check this article on Androidcentral.

Linux desktop performance patch

In my last post, I talked about how improvements are being made to the performance of the Linux block layer. This morning, I saw this article on Phoronix which talks about a kernel patch for improving the interactive performance of the Linux kernel. As you can see in the videos below, it really makes a difference.

Patch applied, but disabled:

Patch enabled:

For the full details, see this page.

Optimizing the Linux block layer for SSD performance

Today I finally got around to reading this interesting article I found on LWN.net some time back. It deals with the challenges of optimizing the Linux block layer for todays SSD drive performance. If you’re interested in those kinds of things, then take a couple of minutes and read it through. It’s definitely worth the time!

More Android exploits

As I pointed out in a previous post, Android is, if used incorrectly, just as insecure as any normal PC. After writing that post, a few reports on exploitable vulnerabilites in Android has surfaced.

There seems to be a bug in the credentials manager, which can be exploited to install applications without the users approval:

http://news.cnet.com/8301-27080_3-20022545-245.html
http://www.swedroid.se/sakerhetshal-i-android-funnet-android-1-x-till-2-2-drabbat/ (In Swedish)
http://www.idg.se/2.1085/1.352716/android-drabbat-av-allvarlig-bugg/ (Also in Swedish)

There is also a vulnerability in the browser in most Android phones on the market today:

http://www.securecomputing.net.au/News/237976,android-exploit-code-published.aspx

In addition to this, on November 2, Coverity Inc., famous for its array of various code analysis software, published a report about a number of potential security issues in the Linux kernel used in Android:

http://www.coverity.com/html/press/coverity-scan-2010-report-reveals-high-risk-software-flaws-in-android.html

So, as already pointed out: Be careful about which applications you download and which web sites you visit with your Android phone (or any network capable device, for that matter)!

Encoding videos for Android with mencoder

I have a Sony Ericsson X10 which I watch a lot of videos on, mainly in bed before I go to sleep. While I mostly watch YouTube clips and such, sometimes I watch episodes of TV series which I put on the SD card. Unfortunately, Android doesn’t willingly play the normal PC video formats, and especially not H.264 encoded HD files, so I need to reencode the files to MPEG4.

Previously, I have been using FFmpeg to reencode my videos, mostly due to its relatively simple command line syntax. Today, I wanted to try mencoder instead, because I really like the flexibility it delivers. I don’t know if FFmpeg has the same features; at least I haven’t found them. I struggled a bit before finding good parameters to create a video file which Android can actually play. In the end, I settled for this command line:

mencoder -o test.3gp -ovc lavc -oac lavc
 -lavcopts vcodec=mpeg4:acodec=libfaac:vbitrate=800:abitrate=192:vglobal=1:aglobal=1
 -of lavf -lavfopts format=3gp -noskip -noautoexpand -vf dsize=854:480:0,scale=0:0,harddup
 -af channels=2,volnorm test.mkv

This can probably be tweaked to produce files which suit you better, but at least it’s a start.

Is Linux really an alternative on the Desktop?

I just read this article over at PCWorld. Sadly, I have to agree with everything in it. Linux as a Desktop OS is fantastic, if you know how to configure it, and if you can live without all the good content which is available for Windows or Mac OS X. Those are two huge “if”s, though. I personally use Linux for much of my daily work, and basically for everything that’s related to programming in any way. However, I have to go back to Windows much too often to play games, listen to music, watch movies, etc. Sure, I can run most of the programs in Wine, but it just doesn’t feel right.

For Linux to become a good Desktop OS, it would definitely need some love from the big software companies. As an example, a little while ago, there were rumors about Steam coming to Linux. Things like that would really help Linux adoption. Unfortunately, it’s too hard for software developers to support Linux. Sure, the program can probably run on every distribution out there, but the method of installing applications can be completely different from one distribution to another, and this is hell for a developer. After all, if it’s hard to install applications no normal desktop user will choose Linux, and the fewer users Linux has, the less meaningful it is for software companies to develop applications for it.

Free software advocates might not think this is a bad thing. After all, a common way of thinking in the Linux world is that software is supposed to be free, and that the Linux world shouldn’t be polluted by closed, proprietary, software. This is a good philosophy, but the facts cannot be ignored. Many good software products are written by large companies, and these companies want to earn money from it.

Personally, I wouldn’t mind running a couple of proprietary applications in Linux, if that let me do everything I want. I don’t hate Windows; I actually think it’s perfectly OK. However, Linux improves my productivity with its outstanding scripting abilities. unmatched by anything I have seen for Windows. If I could get just one OS which fulfills all my needs I would be happy. Unfortunately, I don’t think Linux will be that OS anytime soon…

Is Android secure?

There’s been a lot of talk lately in swedish media about the security of smart phones. This news report (in swedish) by the swedish public service TV station SVT shows how easy it is to hack into your iPhone and do all kinds of weird stuff, such as recording audio using the phone’s microphone or sending an SMS.

Following that report the well known swedish Android site Swedroid published an interview (also in swedish) about the security of Android. This post is written in response to that interview.
Read more »

Linux on the BeagleBoard, Part 1 – Introduction

This entry is part of 1 in the series Linux on the BeagleBoard

Running Linux on the BeagleBoard is fairly simple. There are tons of images floating around with all kinds of Linux installations. However, if you are like me, you will at some point want to know how it all works, and build your own system from scratch. Doing so might seem hard to begin with, but it’s actually quite simple.

In this article series I will try to guide you through all the steps you need to take to get a basic Linux system up and running on the BeagleBoard. I will start by explaining how to build your toolchain, then move on to building the Linux kernel itself, and finally demonstrate how to build a filesystem containing applications which run on top of that Linux kernel.

To follow this series, you need to have some basic understanding of Linux and how to use the shell. You do not, however, have to be some kind of Linux guru!