Ubuntu mkdir permission denied

I was trying to mount dvd-rom in Ubuntu server yesterday. So I create a directory named dvd under /mnt directory. I always create a different directory for different devices I mount into my Linux system such as usb thumb drive, external hard disk, etc. So I try to do the same in Ubuntu, but I got this ubuntu mkdir permission denied warning though.
Ubuntu mkdir permission denied warning:
luzar@ubuntu:~$ mkdir /mnt/dvd
mkdir: cannot create directory `/mnt/dvd': Permission denied
luzar@ubuntu:~$

I have permission denied warning. That means I don't have permission to create directory in /mnt directory. So here's what I do:
luzar@ubuntu:~$ sudo mkdir /mnt/dvd
[sudo] password for luzar:
luzar@ubuntu:~$ ls /mnt
dvd

If you are using other Linux distributions, probably you are doing your job as root. In Ubuntu, the safety precaution has been taken, where in default installation, root account has been disabled. So user just create a normal user during the installation. Of course the root account is created by default in all Linux installation, and so does in Ubuntu.

The ubuntu mkdir permission denied issue has been solved. We learn a useful tips here. Please remember, in Linux, the warning message is important because it tells us what the problem is.