Western Digital's documentation is very explicit that it, Western Digital, knows nothing about Linux. It only mentions that there may exist "generic" drivers. Not aware of that problem -- it is not mentioned on the box -- I bought a WD "My Passport" external hard disk. I plugged it into my computer running Ubuntu Linux and immediately saw that Linux could read and write the disk. So I would not have to reformat the disk, as do the poor Mac users. The only question was to find appropriate, reliable, free software to manage the backups.
Anything Windows can do Linux can do better,
Linux can do anything better than Windows,
I set out to find out what Linux had to offer.
The answer -- or at least one of a number of answers -- is _ rsync _. It is well explained in Ubuntu Community Documentation, which you can see by clicking here. You should read before going further here.
My system has the complication that it has dual boot and a Windows partition. The first job was to find out what Linux calls the Windows partition and what it calls the external USB hard disk. So I opened a Linux Terminal, and did:
I immediately saw that the external drive was called "My Passport" while the Windows partition was called FC32282f3227ECF8. So I did
cd /media/"My Passport"
sudo rsync -azvv /home/ /media/"My Passport"/LinuxPartition
sudo rsync -azvv /media/FC32282f3227ECF8/ /media/"My Passport"/WindowsPartition
Each of the last two commands may take quite a while when first performed and every byte has to be transferred. Later, rsync figures out what needs to be transferred and the process goes much faster.
The commands above back up Windows itself but do not back up the Linux operating system itself, because it is available on the live CD.
If I may offer a word of unsolicited advice to the folks at WD it would be this: Don't make yourselves sound ignorant to users of your products who have found that Linux is not only virus free and rich in useful, free software but is also easier to use than Windows. Get Linux, play with it, and offer a few words of helpful advice to users of your products with this superior operating system. You don't need to write any software.