Time Machine failing (.inProgress)
The user account named ”root” is a superuser with read and write privileges to more areas of the system.

It is disabled by default since it can do a lots of irreparable damages, so use it with caution.

In Terminal use the Sudo to invoke that root user account, and you will be prompted to enter the password, which is usually your Administrator password. It is just a protection for some powerful commands making sure you want to do that by confirming it with password.

sudo tmutil delete …


Password: .....