Category: Computers

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Solving Slow Firefox Web Browsing and Internet app problem on Ubuntu Karmic 9.10

Though this post might be dated as it concerns about Ubuntu Karmic Koala release (9.10), but nevertheless the problem can be considered as annoying and serious.

Bug Symptom
People who encountered this bug may report that web browsing speed is relatively slow compared to the internet speed as tested with http://speedtest.net, and some application which uses internet is behaving like it was having problems with network connection.

Actual problem
According to Ubuntu bug report #417757, this problem is caused by DNS resolver which attempts to request IPV6 AAAA record first. The problem is noticeable on application which supports IPV6, where the getaddrinfo() will ask for AAAA record which the DNS resolver does not understand. This will cause the DNS resolver to reject the request and caused a time out on the client side, which in turn cause the delay.

For a web browsing application like Mozilla Firefox, an average website would normally take about 4-10 DNS request and hence the effect would be more noticeable on web browser, making it look like the network is having problems with slow internet connections.

Solutions
The solution for this problem is to install a local DNS resolver (sudo apt-get install pdns-resolver) and to edit the “/etc/resolve.conf” file, changing the ‘nameserver’ parameter to 127.0.0.1

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How to use rsync to backup and synchronize files to USB drive

Portable USB drive (sometimes called pendrive) has gained popularity as a medium for storing documents. Computer users would work on the files that they store on the usb drive and occasionally would copy them on their computer, or vice versa.

However this would cause problems if there’s a lot of files being worked on and transfered between usb drive and computers. Valuable time might be lost solely for identifying which of the files are more recent and need to be updated.

Fortunately there’s ‘rsync’, a tool which can be used to synchronize files between the computer and usb drive. Assuming you use Debian or Ubuntu, you only need to start ‘synaptic’ and select ‘rsync’ package. Once installed, start the terminal application and you can begin synchronizing the files using this command


$ rsync -r -vv /home/username/Documents/ /media/your_usb_drive

The general format of rsync command is :

$ rsync -r -vv <local document directory> <remote backup directory>

rsync only updates file which has been changed and would save time and precious harddisk space from maintaining duplicate files.

A Windows version is also available at : http://www.rsync.net/resources/binaries/cwRsync_3.1.0_Installer.zip

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Quick Way to upgrade to Ubuntu 10.10 Maverick Meerkat

Ubuntu 10.10 Maverick Meerkat release is just around the corner!

Here’s how to upgrade Ubuntu 10.10 Maverick Meerkat using bash shell

sudo sed -i 's/lucid/maverick/g' /etc/apt/sources.list && sudo aptitude update && sudo aptitude dist-upgrade

sudo aptitude install update-manager-core
sudo do-release-upgrade -d

That’s it! Happy upgrading!

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How to make JavaME .jar files downloadable from Apache Web Server

Mobile application developers may have realize that one of the best (and recommended) way to distribute their JavaME/J2ME application is by hosting it on a website. This makes it easier for potential users to navigate and download the .jad or .jar files from their phone browsers and to execute it directly.

However, some web servers are not configured to handle .jar / .jad file requests, eventually leading to failed install response received by the mobile users.

To remedy this, .jad / .jar files need to be associated with the correct MIME type. In Apache, you can do this by creating ‘.htaccess’ file in your web directory, and inserting these lines :

# JavaME
AddType text/vnd.sun.j2me.app-descriptor .jad
AddType application/java-archive .jar

Afterwards, safe the file. The web server should behave accordingly when requests are made to either of these files. For other web servers, please refer to their respective manual or online-help on how to change document MIME type.

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Ubuntu Tutorial Video from Screencast.Ubuntu.com

Reading through dozens of paragraphs, just to learn the basics of Ubuntu can be tedious, especially for those who don’t have much time on their hands to figure out about Ubuntu software repositories system. The good news is, they no longer have to read through articles full of vague descriptions anymore, instead they can get visual tutorial from Ubuntu Screencasts website!

The video listed on the website covers popular topics that would be asked by Ubuntu newcomers and is very easy to follow as it has narration. The videos are also available in high quality downloads (1280×720 resolutions) in several common media formats (flv, ogg, mp4).

The site is also updated weekly, and is one of Ubuntu sites that you shall not miss – Ubuntu Screencasts

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Simmbook – an affordable $190 Business Netbook, with Ubuntu !

Behold! Simmtronics has launched its latest product, the Simmbook which is a netbook, priced at $190 only! The netbook is geared towards business users as it includes IBM Lotus Symphony, SmartWork client suite and various other IBM cloud-based services. The Netbook specs 10-inch display, Atom N270 processor, 1GB of RAM, three-cell battery, and a 160GB hard drive.

Best of all, it comes with Ubuntu pre-installed.