This tutorial will show you how to allocate drive space in case of Ubuntu 11.04 (Natty Narwhal). Now suppose that we are going to install Ubuntu 11.04 and at first of the installation process we will meet Allocate drive space screen (the most important step in the installation process). In Allocate drive space screen Select Something else to partition your disk drive manually.
# Create / Partition: Select free space and press on Add button.
Ubuntu 11.04 requires about 4.4 GB, So we should type a value more than 4.4 GB, Here in my case i put 6000 MB i.e 6 GB, From Use as i selected Ext4 journaling file system and from mount point i selected / .Press Add button to create / partition.
Now we successfully created / partition as sda2 as shown below
Now we have / partition and Swap so we are ready to install Ubuntu 11.04 (Natty Narwhal). To start installation process press Install now button.