VirtualBox Installation with Centos 6.6
Step 1: Retrieve and Install VirtualBox
Download and install VirtualBox 4.3.30 from here for your platform.
Step 2: Start up VirtualBox and install Extension Pack
Once VirtualBox has been started up download and install the VirtualBox 5.0 Oracle VM VirtualBox Extension Pack from here.
Step 3: Download the Centos 6.6 Virtual Computer VDI File
Download the CentOS 6.6 x86_64 Full Desktop VirtualBox VDI Virtual Computer from here. The file is a .rar archive file. Upon extraction, it should create a directory that contains a file called
CentOS-6.6-x86_64-Desktop.vdi
Step 4: Create a Centos 6.6 Virtual Machine within VirtualBox
In VirtualBox, click on "New" to create a new virtual machine. Assign a name to the virtual machine. The type should be "Linux", and the version should be "Red Hat (64 bit)". On the next screen, accept the default memory size. On the screen after that, choose the "Use an existing virtual hard drive", and then specify the CentOS-6.6-x86_64-Desktop.vdi that you downloaded in Step 3 above.
Step 5: Set up Local Account
Once Step 4 is completed, VirtualBox should boot your virtual machine automatically (if it does not, just press the "Start" arrow), and bring you to a Centos login screen. The first time, you need to login as the adminuser. The password is adminuser. This is also the default root password.
After you have logged in, choose System->Administration->Users and Groups. You will have to authenticate using the root password (adminuser). Click on "Add User", and add a new local user, by specifying the username, full name, and password. The other defaults are fine.
You also need to give this new local user permission to do certain system level things, by adding the user to something called the sudoers list. To do this, complete the following (you will need to respond with the root password at the first command):
su
export EDITOR=gedit
visudo
This will bring up the sudoers.tmp file in a gedit window. Add the following line to the end of this file:
localuser ALL=(ALL) ALL
where 'localuser' is replaced with the username of the local user that you have created. Save and exit the editor.
Once you have done this, choose System->Log Out adminuser, and then log back into the Centos virtual machine using the local account that you just created.