Though I do not work for them, I've been using Image For Linux for at least 10-years now. It is the sister product to Image For Windows, and, IMO, the far superior option for backing up ANY bootable drive. I have it installed, itself, on a bootable USB drive.
The fact that it nags you to purchase it is a moot complaint, IMO. It is inexpensive enough, $29.99 and $39.99 if you buy BootIT Bare Metal (Image for DOS comes with the package and before you say WTF? DOS, you should check it out with its 30-day trial period) - an unbeatable partition manager, that most people could probably easily afford it. That price entitles you to all upgrades within a major version number, and the license is good for use on three PCs. They do not churn major version numbers, either. I bought 2.X well over 10-years ago, and it was only about a year or two ago that they went to 3.X. The upgrade was something like $19.99 for each license I own.
My apologies for this sounding like a commercial, however, I use Image For Linux as my primary backup utility. It is able to image literally ANY bootable drive to file or to another drive. The files it produces are compatible with Image for Windows and vice-versa. It will automatically resize to different drive sizes and is literally fool-proof IMO. For me, you get an exceptionally powerful tool for a very reasonable price. It has both ANSI graphic and GUI interfaces and is extremely simple to use.
IMO, Image for Windows/Linux/DOS - Yes DOS, is the only way to go.