Change your username -UBUNTU

If you want to change your username

Restart in recovery mode and go to the root prompt shell

 ("Drop to root shell prompt")

1. First remount the root
1. mount -o remount,rw /
2.  change the username and home folder name

1. usermod -l <newname> -d /home/<newname> -m <oldname>
   

3. reboot
4. Resume normal boot

Configure IP of CentOS on virtual box

Once you installed CentOS on virtual box and it's not binded with any IP after issuing the command ifconfig.

Troubleshoot by issuing the following commands

ifdown eth0
ifup eth0
yum update

It will solve the problem.

Reference :

http://stackoverflow.com/questions/20816133/pycurl-error-6-couldnt-resolve-host-mirrorlist-centos-org