IMHO the best free tool to clone whole disk or few partitions is Clonezilla.
- it's free and open source
- it supports many file systems
- it's reliable - i didn't have any issues with it
- it can clone disk with bad sectors and you can boot it (tested on broken windows disk)
- it's free and open source - It could be a problem for somebody
- choosing right options could be tricky
In most cases you can use `Beginner mode` and click next, next... like in windows :P. Ofc you need to choose correct source and destination disk :) The problem is, when you would like to clone bigger disk to smaller one. `Beginner mode` won't allow you to do so. Luckily there is also `Expert mode`, where you can choose correct flags. Remember, that your data needs to fit in smaller disk, so you won't be able to put full 512 gb disk in 256 gb :).
Besides standard options you should choose:
-rescue in case of bad sectors,
-icds - in case of smaller destination disk,
-v for more info.
The next best option would be leaving default setting, like on screenshot:
Last step is important - you need to choose
-k1for resizing partition table:
And that's all. After few confirmations the process will start.