Ubuntu Linux is certified by Canonical Ltd. to run on Lenovo ThinkPad X1 Carbon. These instructions are for the old 3rd generation that I bought from Lenovo in 2015, but Ubuntu Linux 16.04 is also certified to run on the 5th generation, but I have not tested these instructions on the 5th generation of Lenovo ThinkPad X1 Carbon. You may risk to loose data and files on your computer by following these instructions, so take a full backup before you install Ubuntu on your ThinkPad X1 Carbon.
If you want to install Ubuntu Linux 17.04 (Zesty Zapus) Beta 2 on Lenovo ThinkPad X1 Carbon (3rd generation), the boot image for 14.10 is required for installation from scratch on this computer. For Lenovo ThinkPad X1 Carbon (5th generation), I think that the boot image for 16.04 is required. You can buy a bootable USB flash drive with 16.04 LTS from the Canonical Store, but I have not tested this on a 3rd generation Lenovo ThinkPad X1 Carbon.
To install Ubuntu on Lenovo ThinkPad X1 Carbon, you must first deactive the Secure Boot by entering the BIOS and turn the option Off.
Then you must download and write the boot image for Ubuntu Linux 14.10 to a USB flash drive with the dd command on an existing Ubuntu system. See the article “How to create a bootable Ubuntu USB flash drive from terminal?” for details on how to write the boot image for Ubuntu Linux 14.10 to the USB flash drive.
Then you can boot the system from the USB flash drive by entering the BIOS and select the USB flash drive as the boot medium and run the installer. After you have installed Ubuntu, you must boot the system for the first time and press the Ctrl + Alt + 't' keys to open the Terminal window, connect to and configure the local network by running sudo start network-manager and enter sudo do-release-upgrade -d to upgrade the distribution from 14.10 to 15.04 and from 15.04 to 15.10. You cannot upgrade to 16.10 from Ubuntu 15.10, so you have to manually upgrade apt from Ubuntu 16.04 with dpkg and manually upgrade to Ubuntu 16.10 from Ubuntu 16.04.