iMac won't start after SD clone completes

[tuni]

I read in the SD manual: "its easiest to log out of your account, and then log back in with the Shift key held down. This will prevent your startup items from running, and helps to esure that your personal data doesn't change during the backup."

So what I've been doing is selecting, "restart" then when machine closes, holding down the Shift key until the Apple logo appears and asks for my Apple ID....

Isn't that the correct way to do it, prior to beginning the SD cloning process??????? I do see a notification that I am in "safe mode" on the top right hand side of my desktop?????