I keep hearing this, but as a Mac user who uses Time Machine and CCC, what's a good way to test the backups? After all deleting my only system to attempt a restore seems even more dangerous.
Here's a way to do it. You need to feel comfortable around the OS X terminal command line. You only rely on OS X's built in programs, so it's an independent way to check if your backup program is doing the right thing.
Then I would run the same type of script in the destination directory and diff the results.
There are some annoyances. E.g. (from memory) the ~/Library/Caches files aren't backed up, so they will be missing at the destination. I wrote some sed commands to first remove some of these from the result checksums to keep my diff's more manageable.
Instead of the above, I currently use a Python script that I wrote, that let me fine tune things. At the heart of it is (as root, of course) using Python's os.walk to traverse a directory tree. For each file I use hashlib.sha256 to generate a checksum. I also don't descend into certain directories. Etc.
Using a few Python scripts to generate and process the source and destination checksums allows me to, at the end, use a simple
vimdiff source.checksums destination.checksums
to quickly see the few differences that remain.
Keep in mind that the perfect is the enemy of the "good enough". Just using the basic 'find' (and not a custom Python script) is plenty good. I used that method for many years.
Many errors stick out right away. E.g. if you have 1,000,000 files checksummed in your source but only 250,000 in your destination, then you quickly know that you screwed up.
