misc online_course, education

Last week another online course started at Stanford University called An Introduction to Computer Networks. It started on 8th of October and they released a good deal of materials for the first week. I hope I’ll follow it until the end. If you’re interested you better hurry up because it’s not easy to catch once the videos pile up!

Here’s the link to access the site: https://class.stanford.edu/networking

UPDATE: The above link seems to have stopped working. This should be the current one now: Stanford CS144 Networking Class

misc site_news

I’ve been postponing this for a long time but finally I did it: I started using AWS (Amazon Web Services). My blog doesn’t get too much traffic so actually I don’t need the scalability which is EC2’s strongest point but I wanted to play with the cloud so decided to move my blog first. It’s quite easy to do so and I’ll explain how to migrate your existing blog to cloud within minutes:

STEP 01: Backup your existing blog

mysqldump -u root –p {database name} > blog_backup.sql

Download your wordpress installation folder and the backup you just created from your existing server. I Used WinSCP to get my files. It can be downloaded here.

STEP 02: Create AWS EC2 instance

Fun part starts now. Login to your AWS account and go to EC2 console. Click Launch Instance and follow the wizard. For my blog, I selected a Micro instance but it depends on your needs. I selected a 64-bit Amazon Linux AMI for the instance.

STEP 03: Assign an IP to your server*</span>

Our machine has just started running but to update our domain’s DNS records we need an IP. On the left menu, click the Elastic IPs link and allocate a new IP address. The IPs assigned to EC2 instances are free.


Right click on the IP and select Associate and choose your instance. After this step we have a running machine with a public IP.

STEP 04: SSH into the machine

By default SSH is enabled you must have created a keypair to access your machine during the Step 2. I use putty to as my SSH client which can be downloaded from here. It’s best to switch to root during the installations. So type:

sudo su

STEP 05: Install required programs

First install Apache:

yum install httpd

Then PHP:

yum install php php-mysql

Then MySQL:

yum install mysql-server

If you use SSL like me you also need to install SSL module for Apache:

yum install mod_ssl

Start Apache and MySQL

service httpd start

service mysqld start

STEP 06: Customize MySQL and import your blog

  1. Run the following command to set root password and harden the default installation


  2. Login to MySQL

    mysql -u root –p

  3. Create your database, user and grant access to that user

    create database {database name};

    create user ‘{user name}’@’localhost’ identified by ‘{password}’;

    grant all privileges on {database name}.* to ‘{user name}’@’localhost’ with grant option;

  4. Switch to database and import data

    use {database name}’;

    source {path/to/mysqldump file you uploaded}

STEP 07: Copy blog files

Copy the Wordpress files you uploaded under /var/www/html/{directory name}

STEP 08: Configure Apache

Enter the command to edit configration file:

vi /etc/httpd/conf/httpd.conf

Go down to the end of the file and create a new virtual host by this:

NameVirtualHost *:80
<VirtualHost *:80>
	ServerAdmin webmaster@localhost
	DocumentRoot /var/www/html/{directory name}
	ServerName {Your domain name}
	ServerAlias www.{Your domain name}

And restart the Apache service:

service httpd restart

STEP 09: Enable access to FTP, HTTP and HTTPS

One last step before testing your blog is opening port 21 (for installing themes, plugins etc.) 80 (for viewing!), and 443 (if you’re going to use SSL) on the AWS EC2 console. For this, click on the Security Groups on the left menu. Add the ports and press Add Rule and then Apply Rule Changes.

STEP 10: Install FTP server

  1. Enter the following command and install the FTP server:

    yum install vsftpd

  2. Create a certificate to be used with FTPS connections:

    openssl req -x509 -nodes -days 365 -newkey rsa:1024 -keyout /etc/vsftpd/vsftpd.pem -out /etc/vsftpd/vsftpd.pem

  3. Edit the configuration file:

    vi /etc/vsftpd/vsftpd.conf

    Disable anonymous access and add these lines to the end of the file. Then save the file and exit:

  4. Start the service

    service vsftpd start

  5. Create a user for FTP access and set the password

    useradd {user name} passwd {user name}

STEP 11 (Optional):

If you don’t want to enter the FTP credentials every time, you can
set them in the wp-config.php file:

 define('FTP_BASE', '/var/www/html/{folder name}/');
 define('FTP_CONTENT_DIR', '/var/www/html/{folder name}/wp-content/');
 define('FTP_PLUGIN_DIR ', '/var/www/html/{folder name}/wp-content/plugins/');
 define('FTP_USER', '{user name}');
 define('FTP_PASS', '{password});
 define('FTP_HOST', {hostname]');
 define('FTP_SSL', true);

STEP 12 (Optional): Install SSL certificate for the blog

This step is optional, but using SSL is strongly recommended when connecting to your blog as administrator

Upload your private key and certificate files to your server and copy them under SSL folder:

mkdir /etc/ssl/private<br />
mv filename.key /etc/ssl/private/<br />
mv filename.crt /etc/ssl/certs/<br />
mv CARootCert.crt /etc/ssl/certs/<br />

Modify Apache configuration file for SSL:

NameVirtualHost *:443
<VirtualHost *:443>
 DocumentRoot /var/www/html/{folder name}
 ServerName {domain name}
 ServerAlias www.{domain name}
 SSLEngine on
 SSLProtocol all –SSLv2
 SSLCertificateFile /etc/ssl/certs/filename.crt
 SSLCertificateKeyFile /etc/ssl/private/filename.key
 SSLCACertificateFile /etc/ssl/certs/CARootCert.crt

STEP 13 (Optional):

If you get an “Unable to locate Themes directory” error add the following snippet to wp-config.php.

if(is_admin()) {
 add_filter('filesystem_method', create_function('$a', 'return &quot;direct&quot;;' ));
 define( 'FS_CHMOD_DIR', 0751 );

STEP 14: Enjoy!

That’s it! You installed a Wordpress application, imported your old posts, secured your blog with FTPS and HTTPS access. Time to celebrate!

misc online_course, education

Recently there is an explosion in the online courses for higher education. It’s a great chance for people looking for comprehensive academic classes. I started with a bunch of these classes but time proved that I should have selected wisely. Because they are not fluffy little tutorials. You really have to take the time to watch the videos, take the exams and hand in the assignments. So here are the ones that I find useful mixed with some of the older resources I used for similar purposes.


Udacity is one of my favourites. It’s very forgiving about the deadlines. It uses Youtube extensively. You can even take the quizes and answer questions right on the video and submit your results. It has very nice courses including Applied Cryptography and Artificial Intelligence.


Coursera has a ton of Stanford classes like Cryptography, Machine Learning and Computer Networks. I had started Machine Learning course when it was in sort of a beta phase and was running on ml-class.org. Princeton university offers nice computer science classes as well under this site.


I don’t know if this was a beta site but it offers only one class by MIT: Circuits and Electronics. More about MIT courses below…


edX has a small but quality selection of courses from MIT, Harvard and Berkeley. Software as a Service and Artificial Intelligence courses from Berkeley look delicious.

Academic Earth

I personally haven’t tried this site but heard from a friend. From the looks of it I think they have mostly old material. They have some video courses from Stanford which I had seen a few years ago from iTunesU. Still it may worth keeping an eye on.


iTunesU was a gold mine in my eyes when I first discovered it. Watching course from Stanford while commuting was a great way making good use of time. Now the more interactive courses overshadowed it but it’s not dead yet. Far from it. Apple released an iTunesU app which allows to download your favourite courses very easily.

Khan Academy

Frankly I’m not a big fan it. Compared to the rest it has rather simple and entry-level tutorials. But still shoulders an important mission and helps a lot of people get some valuable resources so I thought it’s worth mentioning.