Upgrading to macOS High Sierra has frustrated many users due to issues like security flaws, slow performance, frequent freezes, and installation errors, such as the Mac not booting, grey screen of death, or getting stuck on the installation screen for hours. This article explores solutions to fix the “Mac not booting after a High Sierra upgrade” error.
Before attempting fixes, back up or recover data from your unbootable Mac using Remo Recover to avoid data loss. Follow these simple and effective methods to resolve the black screen issue on mac.
Step 1: Recover data from not booting Mac using Remo Recover Mac
Download the Remo Recover (Mac) tool and recover data first before performing any fixes. Some of the troubleshooting methods may delete data from your system. It’s better to secure your data before you go ahead. Follow the below-explained steps to backup & recover data from a not booting Mac after High Sierra Update.
Easy Steps to Backup / Recover Data from Unbootable Mac using Remo Recover Mac
First, remove your unbootable Mac’s hard drive and connect it to a healthy Mac. Then, download and install Remo Recover Mac on the healthy system and proceed with the recovery process using the steps below.
1. Launch the software, select the volume or drive from which you want to recover data, and click on Scan.
NOTE: If you couldn’t locate your volume or drive Click on Can’t find the drive? option to locate it.
2. Click on Dynamic Recovery View to see the device’s recovered data.
3. Find the recovered data from the Mac on Lost and Found or Deleted Files folders
4. Double-click to preview the recovered data.
5. You can click the Recover button to save the recovered files from the drive to your preferred location.
Caution: Save the recovered data from the drive in a different location from the previous one to avoid losing them again.
Note: The software works with all versions of Mac OS 10.5 and above.
Now that you have your data recovered, you are all set to proceed with the troubleshooting steps to resolve your Mac’s booting issues.
Step 2: Quick Methods to Fix ‘Mac won’t boot after High Sierra upgrade’
Solution 1: Reset SMC on your Mac
An upgrade to High Sierra may have changed certain default values and settings on your Mac. Resetting SMC may help restore those settings to make it compatible with the new Mac OS. To reset SMC, follow the steps below.
- Power OFF your Mac and connect it to a power adapter
- Press Shift + Control + Option keys along with Power button
- Then release all the keys at once including the Power You will notice that the small light on the MagSafe adapter will change color indicating that the SMC has reset
- Then power ON your Mac the usual way and check if it resolves the issue.
Solution 2: Boot in Safe Mode
Safe Mode in Mac repairs issues with your start-up disk and directories. To boot your Mac in Safe Mode, restart your Mac and when you hear the start-up chime, press the Shift key. When you see the Apple logo, release the Shift key and wait for your Mac to start in Safe Mode. Please note that this may take a while as the repair process takes place in the background.
If the repair is successful and your Mac starts in Safe Mode, you may be able to boot normally. If this doesn’t help, proceed with the next step.
Solution 3: Reinstall Mac OS from Recovery Mode
If your Mac fails to boot after a High Sierra update, the installation process may have encountered an issue. Reinstalling macOS can help. Here’s how:
- Restart your Mac and immediately hold Command + R keys after hearing the startup chime.
- When the Utilities screen appears, select “Reinstall macOS” and follow the onscreen instructions to complete the installation.
- After installation, your Mac should boot normally.
If you face issues updating to High Sierra or get stuck during the update, follow the linked steps to fix High Sierra update errors quickly.
Good to know
To be on the safe side, always have a backup of all your files before you attempt re-installation or any other repair process that may delete data. If you’re using a Mac, take advantage of the Time Machine feature. If you don’t have Time Machine set up, download Remo Recover and protect your data.
