Stefan Helander

Disable 802.11n on Compaq 6910p with iwl4965 in Ubuntu

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I’ve found out that the 802.11n high speed wifi / wlan mode (300 Mbps theoretically) tends to cause more harm than good, i.e. the performance in many, especially crowded, wifi environments will be really poor and it is a better option to turn it off.

My Compaq 6910p laptop comes with an Intel Wireless WiFi Link 4965AGN chipset. The 802.11n mode can be disabled making it fall back to only use 802.11a/b/g modes casuing the connection to be much more stable and often the overall bandwidth will be better.

To check if your chipset is running with 802.11n enabled, enter the command:

sudo iwconfig wlan0

The output will look something like this:

wlan0     IEEE 802.11abgn  ESSID:"XXXXXX"
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:0C:F6:82:90:28
          Bit Rate=14.4 Mb/s   Tx-Power=15 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=51/70  Signal level=-59 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:66  Invalid misc:36   Missed beacon:0

If the first line says 802.11abgn your chipset has 802.11n activated.

To disable 802.11n mode do the following:

sudo modprobe -r iwl4965
sudo modprobe iwl4965 11n_disable=1

This will disable 802.11n until next reboot. Now check again with sudo iwconfig wlan0 and the output should display the first line without the “n” after 802.11, like this:

wlan0     IEEE 802.11abg  ESSID:”XXXXXX”
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:0C:F6:82:90:28
          Bit Rate=54 Mb/s   Tx-Power=15 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=46/70  Signal level=-64 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:7  Invalid misc:485   Missed beacon:0

If you want to make this change permanent, i.e. always disable 802.11n, do the following:

sudo echo "options iwl4965 11n_disable=1" >> /etc/modprobe.d/iwl4965.conf

After rebooting, verify using sudo iwconfig wlan0 that 802.11n is not enabled.

 

Stefan Helander

Samsung Ultrabook series 5 loses wifi connection intermittently

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On a rather new Samsung Ultrabook series 5 we had intermittent / sporadic connection problems on some wifi networks. The status for the network shifts forth and back between ok and “No internet access”. This doesn’t happen on all wifi networks. It seems the problem is the 802.11n mode, especially in a crowded wifi environment.

The solution (or workaround) is to disable the 802.11n mode in the wifi driver for the Intel(R) Centrino(R) Advanced-N 6235 chipset. This gives a lower bandwidth connection but on the other hand, a stable connection.

  1. Go to the Control panel
  2. Open Network connections (search for it if you have troble to find it)
  3. Right click on your wifi connection and select Properties
  4. Click Configure in the upper part of the box (my screenshot is danish, so it is the button labeled “Konfigurer…”)

    Intel Centrino Advanced N-6235

    Intel Centrino Advanced N-6235

  5. Click on the Advanced tab
  6. Find the 802.11n mode status configuration parameter and select to set it inactive (off)
  7. Click Save / OK in the bottom

 

 

Stefan Helander

VirtueMart not displaying in Components menu after install [solved]

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After installing VirtueMart on a Joomla 2.5 site, it should occur in the Components menu in the Joomla! backend. In my case, it didn’t show up.

The problem can be caused by the Xmap – Virtuemart plugin not being enabled.

Solution: 

Go to the Extensions menu and then select Plug-in Manager.
In the filter box, type "xmap" and press enter.
In the list displaying, check if the Xmap – Virtuemart plugin is disabled (status icon is red).
Then click the status icon for Xmap – Virtuemart so it turns green. Now VirtueMart should be availible in the Components menu.

 

Enabled VirtueMart Xmap plugin
Stefan Helander

Fix the Heartbleed Bug on Ubuntu

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OpenSSL on Ubuntu can be vulnerable to the Heartbleed Bug. Not all versions of OpenSSL are affected though. 

OpenSSL version 1.0.1 to 1.0.1f are vulnerable.
OpenSSL version 1.0.1g are not vulnerable.
OpenSSL branches 1.0.0 and 0.9.8 are not vulnerable.

To fix this issue on Ubuntu systems: 

Check your OpenSSL version to see if it is vulnerable to the bug:

openssl version

If it says 1.0.1 check the build date:

openssl version -b

If it says anything before Apr 7 2014 you need to update OpenSSL. Proceed as follows:

sudo apt-get update
sudo apt-get install openssl
sudo apt-get install libssl1.0.0

Now verify that you are running the updated OpenSSL libraries:

openssl version
openssl version -b

The build date should now come out Apr 7 2014 or later.

Now you need to regenerate your SSL certificates as they might been compromised. A guide can be found here: https://www.digitalocean.com/community/articles/how-to-create-a-ssl-certificate-on-apache-for-ubuntu-12-04