I found answer near to this question but not exact answer in Ubuntu-forums.I found answer to

1. How to create swap partition after installing Ubuntu.


2. How to create or add swap file to existing swap partition.

But now for this question.
Since at the time of installation i don't know the use of swap partition, i installed Ubuntu 12.10 without swap partition and i used second method as mentioned in "http://www.thegeekstuff.com/2010/08/how-to-add-swap-space/" to create swapfile and got this error while using mkswap

# mkswap /root/myswapfile

Setting up swapspace version 1, size = 1048572 KiB

**no label, UUID=cc477ba5-e2d9-495c-a63b-300c4e5e0048**

and each time UUID differs. But i ignored and continued with next steps and when i tried to hibernate my system i got these errors

PM: swap header not found,

cannot get swap device try swapon -a,

cannot get swap writer

I just want to hibernate my system only using swapfile without creating swap partition. Is it possible? I'm new to ubuntu.