What To Do If A Mac Won’t Boot After OS Update?
If you keep running an older Mac operating system, you probably will find your newly downloaded apps flash back often or external drives not mounted because of software incompatibility.
Therefore, updating software is necessary.
Before a major OS is released, the Mac will encounter numerous minor OS updates. Either a minor update or a major system upgrade, the computer may have issues after update. The most common issue is that the updated macOS can’t be loaded up after you restart the computer.
How to make the Mac boot successfully?
The best option to save your Mac is to roll back to the previous stable OS version you have used.
For example, if you upgraded to macOS 10.15 Catalina from macOS Mojave but has trouble booting, you had better restore to macOS Mojave. To do it, you have three options.
Option 1: Restore to macOS Mojave if your Mac came with Mojave
Most Macs manufactured during late 2018 and late 2019 came with macOS Mojave.
- Shut down your Mac completely.
- Hit the power button to start the machine and press down Command + Option + Shift + R immediately.
- Release the keys until you see a startup screen. The booting process will take longer than usual.
- Connect the computer to the Internet.
- Select Reinstall macOS in macOS Utilities window.
- Click Continue and follow the onscreen instructions.
Option 2: use Time Machine backup
If you were well-prepared before macOS upgrade, you must have Time Machine backup disk by hand. Using Time Machine backup to restore system and files is easy and efficient and you don’t worry about data loss at all.
- Shut down your Mac completely.
- Hit the power button to start the machine and press down Command + R immediately.
- Release the keys until you see a startup screen. The booting process will take longer than usual.
- Connect the backup disk to the computer.
- Select Restore From Time Machine Backup in macOS Utilities window and click Continue.
- Select the backup disk as the resource disk and click Continue.
- Input administrator password if asked.
- Select a backup in the list (usually the one with latest backup time) and click Continue.
- Select a destination disk (usually the startup disk, Macintosh HD) and click Restore.
- Input administer password again if asked.
After the restoration is done, restart your Mac.
Option 3: Restore from a local snapshot (only work for Mac came with macOS 10.13 and later)
APFS has a feature which can record the state of the file system at a certain point of time and the state is stored locally on the hard disk or/and Time Machine backup disk. That is called APFS snapshots. Usually when the OS is updating the snapshots will be taken and updated automatically, but it is not guaranteed. Therefore, this method has data loss risk because the snapshots may not be the latest state of the APFS file system. If you have to use a snapshot to restore a Mac, do remember to save files with data recovery software first.
The steps to restore to previous state of APFS file system is very similar to using Time Machine backup.
- Shut down your Mac completely.
- Hit the power button to start the machine and press down Command + R immediately.
- Release the keys until you see a startup screen. The booting process will take longer than usual.
- Select Restore From Time Machine Backup in macOS Utilities window and click Continue.
- Select the startup disk (Macintosh HD) as the resource disk and click Continue.
- Input administrator password if asked.
- Select a snapshot in the list (usually the one with latest time) and click Continue.
- Input administer password again if asked.
Conclusion
Hopefully those methods can help your Mac boot up again. If you tried other approaches and they worked, please comment below to share your ideas.
