Disk Cloning utilities?

Can anyone let best disk cloning utilities for live systems.
Ex: a bit locker encrypted laptop was given with decryption key then what will be the best tools/utilities to clone that system.

Try Symantec Ghost or something similar.

Ftkimager is still a good choice

Your cheapest option is to boot the system (as administrator) and make images per partition (/dev/sdX). Thes will not be encrypted. You can use any variant of good old dd (like ddrescue), but my personal preference would be FTK Imager, like rknudsen already suggested.
If you can spend the money, you can use EnCase to make a whole drive image. When opening the image, EnCase accepts the Bitlocker key. This way you get unpartitioned space as well.

A free, simple tool is the dd command on any (free) linux operating system. Make a block-level exact duplicate… helpful for any situation that can be described with the word “Forensics”.

A sample linux command:
sudo dd if=/dev/sdb of=/home/username/SleuthKit/forensicsimage.img bs=64K conv=noerror,sync status=progress

In this example, the drive device, mounted in at /dev/sdb will be copied to the file path as an .img file. The additional options shown are my personal preference.

Especially “status=progress”. That one lets you know how much data has copied and at what rate. Otherwise, you’re staring at your terminal for an hour wondering if it’s doing anything.

As far as a disk cloner, not only is this the cheapest (free) it is by far the most stable of anything out there.