Hello vikas kolapudi,
You would need to start adb as root, this requires the image to be built as userdebug, which is similar to the user buildtype with root access and debuggability, otherwise permission will be denied.
For example for the i.MX6Q Sabre SD you would need to configure:
$ lunch sabresd_6dq-userdebug
After that you would just need to run
$ adb root
And after that you can enter the shell with root privileges.
$ adb shell
I hope this helps!