a-maumau

if you can access to the GUI environment, It is very easy using "disks" application.

or might be easy with gdisk/fdisk ?   I'm not sure about this.  

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see the reference for more detail, if you want.
https://richardstechnotes.wordpress.com/2015/12/18/setting-up-an-nvme-ssd-on-ubuntu-14-04-lts/   http://takatakamanbou.hatenablog.com/entry/2015/10/25/235600 : Japanese website