Using live Linux or custom distros as backup?

Clonezilla can create a complete image or cloned copy for you

Clonezilla is smart enough to copy only used blocks in the file systems (and skip free blocks), and there is compression, if you backup to an image. Clonezilla will also backup the bootloader and partition table. A clonezilla image is a directory with a set of files.

I have used this method for years, and I have restored from the backup to a fresh drive (of at least the same size, not one single byte smaller). Do not boot with both the original drive and the cloned copy connected - it can damage both systems! But when the original drive is removed, or if you restore from the backup to the original drive, it will boot (and behave exactly like the system that was backed up.

Instead of making a [compressed] image, you can clone directly to another drive (of at least the same size, not one single byte smaller). Then you can replace the original drive with the cloned copy and it will work just like the original one.

I think compression is automatic when you create an image, but when you clone directly, there will be no compression. (I think a cloned copy is a waste of drive space, so I store compressed images.) You pick the method that works best for you.

Finally, you should play safe - so test that you get everything correct, test that the backup really works now. Do not wait until the original drive fails, it might be too late to fix a failed backup