Apple recommends downloading all updates in time to keep your Mac healthy and protected from security threats. The latest High Sierra 10.13.3 Supplemental Update also brings important fixes; however, some users report having problems with it. For instance, when a computer reboots, the progress bar may get stuck near the end and stay like this indefinitely.
It is also possible to lose some files because of a troublesome installation. That is why it is always recommended to back up a Mac with Time Machine or other similar apps before installing any system update.
How to Back Up a Mac with Time Machine
Time Machine is a useful built-in tool that keeps a copy of all the data on a Mac. In fact, it makes backups for the past 24 hours every hour; backups for the past month every day; and backups for each month every week by default. However, it saves only the history of changes you have made to files, i.e., the difference between several versions.
To ensure all your data is safe after installing a system update, you must back up your files manually. For this, you need an external storage device with enough space on it – at least 1TB. Alternatively, you can save the information to the cloud. To see how much free space is required, go to the Apple menu, select About This Mac and click Storage.
In order to make a backup with Time Machine:
- Connect an external drive to your computer.
- Your Mac will ask you if you want to use your disk or USB with Time Machine. Choose Use as Backup Disk.
- If it does not ask you about this, go to System Preferences > Time Machine, click Backup Disk, select the storage device you have connected to your Mac and click Use Disk.
- In case you would like to encrypt your backup, you need to come up with a password and enter it.
- Copy the necessary files to the external device.
Install High Sierra 10.13.3 Supplemental Update in a Safe Mode
After you get your data backed up, try installing the update in the Safe Mode.
- Start or restart a Mac by pressing a power button.
- At the same time, you have to press and hold the Shift key until a login window shows up on your display.
- Enter your username and password if you have your startup disk encrypted with File Vault. It means you will be asked to sign in twice: to unlock the startup disk and to log in to Finder.
- Install the High Sierra 10.13.3 Supplemental Update.
- Restart your Mac by pressing only the power button.
High Sierra 10.13.3 Supplemental Update takes much time, so do not panic if the process lasts longer than you expected. The time you will need to spend on this update depends on how much data you are using on your hard drive. For instance, if you have around 800 GB, the update will take nearly 2 hours.