With my Mac I use Disk Utility>Restore to make a bootable copy of its hard drive to an external drive. That ext. drive DOES NOT have to be larger than my internal drive it only has to have enough space for the data being copied. I can use that ext drive to run my Mac or to restore everything to a replacement internal drive if the internal drive fails. How can I do that same thing with Unbuntu on my Dell Mini 9 (DM9)? I have already had a HD/SSD fail in the DM9 and, not having a backup, I had to reinstall everything including documents and the many settings.

I will also try installing MacOSX on that DM9 and use that ext. drive to get back to my Ubuntu setup should I wish.

Thanks.