The thing I wonder why I am not able to see swap area of ubuntu in clonezilla. I want to create an image of my ubuntu. However, I cannot find the swap partition of ubuntu to image it.
The swap partition is not needed.
The swap partition is not needed for cloning. To find out why, let's find out what swap does. If you have programs running, and not enough RAM, they are put in swap. At every boot, and through normal operation, data in swap gets cleared time to time, comes and goes, not being needed for data(Similar to RAM). Keeping SWAP is like taking a snapshot of RAM, which is only useful for debugging. You only need to backup any non-swap partitions related to Ubuntu. If you need to restore, you can make a new swap partition, just like the one you had before, without risking important data.
hexafraction is right. Just one amendment, if one wants to clone a complete disk with a swap partition clonezilla doesn't clone the swap partition but it creates a swap partition. If one restores the disk the swap partition is created but empty.