How do I use tmutil to figure out what's wrong with my Time Machine?

Use

tmutil listbackups

to get a list of existing (completed) backups.

Then run one or both of

tmutil compare # to compare current drive to latest backup
tmutil compare /one/path/from/list /other/path/from/list # compare two backups

You can use timedog to see what's being backed up each time.

Usage:

• Open Terminal (in /Applications/Utilities)

• cd /Volumes/Time\ Machine/Backups.backupdb/[Computer Name] Note Time Machine may be different on your system. Replace [Computer Name] with the name of your computer (see System Preferences => Sharing).

• /path/to/timedog -d 5 -l For instance, if you unzipped timedog to your Desktop, the path would be ~/Desktop/timedog

And then look at the output