Back up everything on your Mac

It is very unlikely that there will be problems upgrading to macos Mojave, but it is better to be safe than risk losing files and so a full backup is essential. There are third-party utilities to do this and Superduper and Carbon Copy Cloner are popular choices. However, Time Machine can be used instead. It does not create bootable backup drives, but it does make a copy of every file on the Mac and they can be restored easily enough.

1 Backup the disk

If you do not have a backup of the disk, plug in a USB drive at least twice the size of the used space on the Mac’s internal drive. Select in System Preferences>time Machine.

2 Check the backup

If Time Machine is in the menu bar, hold down Option, click the icon and select verify Backups. To restore from a Time Machine backup hold Cmd+r just after powering on.