I want to backup my partitions by shrinking it my issue is like
I want to create a new disk copy from only the used blocks I my current image.
How would I redirect the output of resize2fs to new disk and dd the current
partition so that I can boot my new image without issues and also without touching my current image and copying over of only the required data.

I understand that I can copy the entire disk and then resize the cloned disk but this seems inefficient as not all my disk is being used.
I dont want to hinder the current working disk manipulations on this should be avoided as I dont have any other backup.

So suppose I have a 2TB disk of which only 100GB is being used I need only these 100GB in the new disk. Is there any way of copying the used blocks in the existing filesystem to the new filesystem ?

Any pointer or clear ideas would be really useful. I appreciate this if I get some list of commands or steps and doing this without any software.

Not exactly what you asked for, but how about (1) making a partition on your new disk (with your tool of choice, fdisk for example) if you don't already have one, then (2) backing up with rsync -avH /old_data_path /path_to_backup_partition. That should result in a bootable backup (works for me).

Hi Thanks for reply
Does rsync manage size on disk and different partition sizes. I got low disk capacity and hence
different partition table on both disks.

rsync doesn't care about partitions. If the target filesystem isn't big enough, eventually the copy will fail. Else you will have a valid copy.

Would it be efficient to copy entire data, is there any way to just copy over the blocks and adjust them according to the newly created filesystem ?
Would rsync be able to handle the corrupted data like dd can handle since dd does a blind copy. Is there a way of like creating another sparse image file of 2TB then copying over only required data blocks there which will exclude the empty blocks and then resizing the sparse image to 200GB.