Magento : Changing the Admin URL

We can improve security by changing the default URL from 'admin' to something more obscure, such as 'bdadmin'. This will decrease the probability that a malicious user will hit upon your admin log-in page by guessing that the admin site is located at domain.com/admin/, or that automated scripts scanning for Magento admin pages will find it.
To change the admin address you first need to stop Apache and clear the cache:
root# /etc/init.d/apache2 stop
root# rm -rf /var/www/var/cache/*
root# rm -rf /var/www/var/session/*
Then open up the /var/www/app/etc/local.xml file, locate the <frontName> tag, and change the 'admin' part it to something a lot more random,
eg:  <frontName><![CDATA[gJpf2VK5]]></frontName>
Then set Apache running again (bearing in mind your site will be down for the duration of this operation!):
root# /etc/init.d/apache2 start

How to completely uninstall and reinstall Firefox?

You can reinstall firefox with the following command:

sudo apt-get install --reinstall firefox

Creating virtual host in ubuntu

Suppose, the configuration file name is domain.com and local IP address is 127.0.0.1. Type following command in terminal
gksudo gedit /etc/apache2/sites-available/domain.com

Add following lines in configuration file
<VirtualHost 127.0.0.1:80>
    DocumentRoot /var/www/test
    ServerName domain.com
    ServerAlias test.domain.com
    ServerAdmin admin@domain.com
</VirtualHost>

Save and close it. Then create a symbolic link of this configuration file to /etc/apache2/sites-enabled directory in order to enable it
cd /etc/apache2/sites-enabled/
sudo ln -s ../sites-available/domain.com .

Then, add a virtual domain with a specific local IP to hosts file that is located in /etc/hosts. You can also add the port using a colon with the IP.
sudo nano /etc/hosts
add this line
127.0.0.1 test.domain.com
Save and close it. After all restart the apache service.