macOS User Guide
- Work across devices using Continuity
- Use iPhone as a webcam
- Use iPhone with Desk View
- Stream audio and video with AirPlay
- Use one keyboard and mouse to control Mac and iPad
- Hand off between devices
- Unlock your Mac with Apple Watch
- Make and receive phone calls on your Mac
- Sync music, books, and more between devices
- What is Family Sharing?
- Set up Family Sharing
- Add a user or group
- Set up Screen Time for a child
- Share purchases with your family
- Watch and listen together with SharePlay
- Share a Photo Library
- Collaborate on projects
- Find content shared with you
- Find your family and friends
- Play games with your friends
- Resources for your Mac
- Resources for your Apple devices
If the identity of a backup disk has changed on Mac
For security, Time Machine won’t do a backup if it detects that the identity of your backup disk has changed. This can happen for several reasons:
You erased or reformatted your backup disk or partition.
You deleted the disk image for your backup disk.
Someone is trying to steal your information by tricking your Mac into backing up to an unauthorized disk.
If you connect another disk to your Mac, give it a different name from your backup disk. Then make sure your backup disk is correctly identified. On your Mac, choose Apple menu > System Settings > General, click Time Machine , then reselect your backup disk.