macOS Black Book

Well, starting from Sierra, macOS comes with an extra security feature, which doesn't allow any data recovery application to operate. So, after talking with the data recovery company, I was told to execute certain commands from a single user mode, then only the app would be ready. Since, I knew what is this single user mode, I was saved. Actually, this book only discusses macOS shortcut keys. I think such series needs to be next to all mac user.