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December 16, 2017

Ubuntu improve WIFI performance and reliability

If you need a stable internet connection through WIFI then it is important that WIFI performance remains consistent and WIFI connection is reliable at any given time. This is vital if you are running any kind of server or using torrents. Unfortunately, the power management feature exists for different devices within Ubuntu promotes unstable and slow WIFI connection which is enabled by default for WIFI devices. This creates problems such as automatic turning of WIFI and loosing of WIFI connectivity randomly while the system stays idle for a while or there is no inbound packets coming to your system. To check whether you have power management active for your WIFI device execute the following command into the terminal:

iwconfig | grep -w "Power Management"

Now if it is active then you can easily turn it off by executing following command:

sudo iwconfig wlan0 power off

where you have to replace wlan0 word with your WIFI device name which can be found by executing following command:

ifconfig -a

The above command will list all the network devices present in the system including WIFI devices. If the terminal says that command not found then install the program by installing the package net-tools. To do that, execute the following in the terminal:

sudo apt-get install net-tools

Now to make this setting persistent between the boots you can do several things. First, make changes to the /etc/pm/config.d/blacklist file. To do that, in the terminal execute the following to open the file:

sudo gedit /etc/pm/config.d/blacklist

Add the following line in the /etc/pm/config.d/blacklist file:

HOOK_BLACKLIST="wireless"

Second, make changes to the /etc/pm/power.d/wifi_pwr_off file. To do that, in the terminal execute the following to open the file:

sudo gedit /etc/pm/power.d/wifi_pwr_off

Now add the following lines in the /etc/pm/power.d/wifi_pwr_off file:

#!/bin/sh 
/sbin/iwconfig wlan0 power off

Do not forget to replace the word wlan0 with your WIFI device name and save the file. Now, execute the following command it make the file executable upon every boot:

sudo chmod +x /etc/pm/power.d/wifi_pwr_off

Third, make changes to the /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf file. To do that, in the terminal execute the following to open the file:

sudo gedit /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

Now in the /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf file, replace wifi.powersave = 3 with wifi.powersave = 2 and save the file.


That is it!

Cheers!
Imam

December 3, 2017

Yet another HTML cache busting technique

If you are coding your web application or web site from the ground up then you may be already facing problems where changing individual files does not get reflected immediately. This is due to browsers caching some of the files to speed up loading performance and also to save bandwidths. The process of avoiding caching in the browsers is called cache busting.  There are already a ton of solutions out there which can be applied to your HTML code to avoid caching where some are tedious to maintain and others are a breeze. Although not very well known technique here I am presenting how to use hashing technique to do HTML cache busting. This technique can be well applied to both client side or server side scripting languages as well as using any cryptographic hash functions. The method I have selected for my web development is client side PHP scripting language and SHA-1 hash function. Using this method the following HTML code shows how to import external CSS file with cache busting feature:

<link rel="stylesheet" <?php echo "href=\"style1.css?v=" . sha1_file('style1.css') . "\"" ?>>

In the above code, PHP script will inject HREF attribute into the link tag. The ?v=" . sha1_file('style1.css') code fragment will change each time the CSS file is modified as well as add a argument to the CSS file name which will force browsers to load the CSS file. As the SHA-1 hash function is unique each time for a particular CSS file data set the above code works well as intended.

The following code snippet shows that the same technique can be applied to import JavaScript files with cache busting feature:

<script <?php echo "src=\"load.js?v=" . sha1_file('load.js') . "\"" ?>></script>

Cheers!,
Imam

July 4, 2017

Stop Ubuntu from freezing completely with Intel Bay Trail

Ubuntu and Linux kernel seem to suffer from a cpu state bug which completely freezes the system when doing graphics intensive tasks such as playing games or videos. Many processors suffer from this bug including the following Intel processors:

Celeron J1900

Celeron N2940
Celeron N2840
Celeron N2930
Pentium N3520 
Pentium N3530
Pentium N3540

To see whether you have one of the above processor put the following command in the terminal:


cat /proc/cpuinfo | grep 'model name'


This bug can easily be fixed by installing proper Microcode files and changing c-state flag for Linux kernel.


First step is to make sure you have Ubuntu microcode package installed by putting the following command in the terminal:


sudo apt-get install intel-microcode


Then, remove the existing microcode files by running the following command in the terminal as they are not recent:


sudo rm /lib/firmware/intel-ucode/*


After then, install Intel Microcode files by downloading Microcode package from the following site:


https://downloadcenter.intel.com/download/26798/Linux-Processor-Microcode-Data-File


Download the microcode*.tgz file and extract it in the Home folder. Now copy the extracted microcode files to system folder by opening a terminal in intel-ucode folder and running the following command:


sudo * /lib/firmware/intel-ucode/


Now edit the grub file to change c-state kernel flag by opening grub file in /etc folder by putting the following command:


sudo gedit /etc/default/grub


In the grub file under the line containing GRUB_CMDLINE_LINUX_DEFAULT=, add the following intel_idle.max_cstate=2, so the line should look like the following line:


GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_idle.max_cstate=2"


Now, save and close the grub file and put the following command in the terminal to update boot loader to reflect kernel flag:


sudo update-grub


Done! Now just reboot the system and check whether microcodes are loaded properly by running the following command in the terminal:


dmesg | grep microcode


You should be able to see something like following as output of above command:


[    3.168100] microcode: CPU0 sig=0x30678, pf=0x8, revision=0x829

[    3.168138] microcode: CPU1 sig=0x30678, pf=0x8, revision=0x829
[    3.168445] microcode: Microcode Update Driver: v2.01 <tigran@aivazian.fsnet.co.uk>, Peter Oruba

Cheers!