Dell XPS L702xI have a Dell XPS L702x Laptop and the wireless is dodgy in Ubuntu 11.04. By Dodgy I mean it drops out and doesn’t automatically connect very often especially when a Ethernet cable is unplugged. It seems the problem is that Ubuntu doesn’t get on well with wireless-N (perhaps the driver is buggy?). I fixed it by disabling wireless N (but leaving G working):

First check to see that b, g and n is enabled:

> iwconfig
wlan0 IEEE 802.11bgn ESSID:"WKIXNTOM"
we need:
wlan0 IEEE 802.11bg ESSID:"WKIXNTOM"

To disable Wireless N, create a file called /etc/modprobe.d/iwlagn.conf and put the disable incarnation in it:
> sudo vi /etc/modprobe.d/iwlagn.conf
options iwlagn 11n_disable50=1 11n_disable=1

Restart the computer to finish.

I agree this isn’t a ideal solution (to say the least!), but it’ll do for now.

Update after 2 months: Wireless has been reliable and steady since making the above change.

Update (15/Oct/11): This “hack” is a disaster for Ubuntu 11.10 Oneiric Ocelot, it causes Wireless to fail to load. Be sure to remove the /etc/modprobe.d/iwlagn.conf file when upgrading to Ubuntu 11.10. I found this issue the hard way: askubuntu question.

Screenshot of Page Speed in Firebug
I find the Page Speed tool from Google extremely helpful for optimising my websites. I have a tip which can save time if your website is failing the “Optimize Images” test. Using the in-built is one option but if most of your images are jpegs, you can achieve the same result and save time using a command line tool called jpegtran with the -optimise parameter to do lossless compression and the -copy none parameter to strip out image meta-data.

Disclaimer: As with any image processing always keep a copy of the original images.

To install jpegtran in Ubuntu, do:
sudo apt-get install libjpeg-progs

  • To optimise a single jpeg image:
    jpegtran -copy none -optimise -outfile image.jpg image.jpg
  • To optimise all jpegs in the current directory:
    for img in `ls *.jpg`; do jpegtran -copy none -optimise -outfile $img $img; done
  • To optimise all jpegs in the current directory and all child directories:
    find . -name “*.jpg” -print0 | xargs -0 -I filename jpegtran -copy none -optimise -outfile filename filename

If you need to optimise various image formats, there is a PHP CLI tool called smusher which uses and can work recursively on directories. Might be worth a look. It would be nice if had a API – their FAQ mentions they are working on it.