On 7 Sep 2016, at 12:42, Madhu K wrote:

I have one doubt, does all embedded system with Linux as operating system have initrd?

It depends, but many of them do not. (In fact, I’ve not seen any that do use an initrd, but that doesn’t mean they don’t exist.) As the hardware is known the required drivers are built in to the kernel directly. Regards, Kristof