I am new to linux and got install UBUNTU on my system can anyone tell me how can I know on which partition of hdd current OS is installed.
Re: new user
have a look at the text file /etc/fstab. Find "/" in the mountpoint column, and the first entry of that row should say /dev/sdXX (or maybe /dev/hdXX) - that's the partition that the OS is using.
Note that there may be other partitions being used. For instance, some people configure a separate partition for swap space, applications and their home directories.