Resolve Mac Not Booting/Starting After macOS High Sierra Update

Mac Won't Start/Boot After macOS High Sierra Update, Help!

"I updated my iMac to the latest macOS High Sierra last night. Upon finishing the update, I attempted to start the computer, but it wouldn't boot. I attempted a force restart on my Mac, yet nothing appeared on the screen. What other steps can I take to revive the computer and get it functioning again with macOS High Sierra?"

Although Mac hard drive boot failure issue is not a new problem anymore, it can still be a challenging issue for regular users to resolve when their Mac computers fail to boot after updating or installing macOS High Sierra.

Furthermore, to avoid the hassle of losing crucial data, it is advisable to back up your essential files using a tool like Data Recovery Wizard for Mac Pro before installing or updating macOS.

Translate into English

Backup Your Mac and Ensure Data Safety

Backup and restore your MacBook/iMac without using Time Machine, iCloud, or external hard drives.

If you're encountering this issue, don't worry! This tutorial article will guide you on how to promptly fix and resolve the problem where your Mac hard drive won't boot after updating to macOS High Sierra. Simply follow any of the provided methods to get your Mac computer functioning again:

Quick Fix 1: Reset SMC to resolve Mac not booting after High Sierra update

Occasionally, if the Mac computer's cables aren't connected correctly, it might not boot normally. Hence, if your Mac fails to boot after a system update, you can reset the SMC to resolve the issue of your Mac not booting following a macOS High Sierra update:

1. Turn off the Mac computer and disconnect all cables; 2. Wait for a few minutes, and then reconnect the cables; 3. Restart the Mac computer to check if you can access the system.

Quick Fix 2: Force Reboot Mac and Reset NVRAM to Resolve Mac Not Booting Issue

1. Press and hold the Power button for several minutes until the Mac turns off; 2. Wait a few seconds, then press the Power button to turn on your Mac; 3. While starting up your Mac, hold down the Command + Option + P + R keys to reset the NVRAM; 4. Restart your computer again to check if the issue has been resolved.

Note: If these two quick fixes didn't assist, proceed with the comprehensive solutions below to resolve your issue immediately.

Translate into English: Solve "Mac Won't Boot" or "Fails to Boot" Error After macOS High Sierra Update

If you have important data saved in the Mac computer hard drive, remember to restore data before taking steps to fix the Mac won't boot error.

1. Recover data when Mac hard drive won't boot from High Sierra

Professional Mac data recovery software with a bootable disk can efficiently retrieve your data from a Mac hard drive when the computer fails to start up. You can directly buy Tools Data Recovery Wizard for Mac with Bootable Media to create a bootable media for your Mac and use it to restore data from a non-booting Mac computer:

Step 1. Install and run tools Data Recovery Wizard for Mac on another accessible Mac, and choose "Unbootable Mac" mode > "Start".

Step 2. Next, select a prepped USB drive to create the bootable disc. Choose "Next" to commence creating the bootable disk.

Step 3. The program will begin creating a 2GB partition to save the boot files. The remaining space on the USB drive can still be used for storage.

Step 4. Once the process is complete, follow the instructions to boot your corrupted Mac from the bootable disc and initiate recovery. We recommend restoring your data to an external hard drive.

Boot the corrupted Mac from the bootable disc

Step 5. After booting your Mac, open the Data Recovery Wizard for Mac. Select the disk location where you lost your data and files (either an internal HDD/SSD or a removable storage device). The recovery tool will then automatically scan for lost files.

Note: Before attempting data recovery, it's advisable to create a backup of your Mac to prevent further data loss. Once you've backed up your system, the software can retrieve data from the backup, and your computer can proceed to write new data.

2. Resolve the issue of Mac not booting after updating to macOS High Sierra

Follow these methods to resolve the issue where macOS High Sierra fails to boot:

Method 1: Boot Mac in Safe Mode to resolve the Mac not booting issue

1. Power on your Mac and press the Shift key as soon as you hear the startup sound; release it when you see the Apple logo appear; 2. Once your Mac has fully started up, restart the computer normally without holding any keys or buttons. 3. Wait for your Mac computer to complete the reboot process.

Method 2: Use Disk Utility to Restore Mac from Recovery Mode when macOS High Sierra Won't Boot

1. Start up your Mac and press Command + R while it's booting up; 2. Select the Disk Utility option > Click on First Aid and attempt to repair your Mac's disk; 3. Disk Utility will perform an fsck (file system check) operation to assist in fixing the issue of macOS High Sierra failing to boot; 4. If that doesn't work, try restoring from Recovery Mode. 5. In Reinstall OS X in Recovery Mode, the system will automatically download and install the latest version of macOS High Sierra onto your Mac device.

Method 3: Use Terminal to repair the 'Mac hard drive won't boot' error caused by High Sierra update

1. Open Terminal > Applications > Utilities;
Type: system_profiler SPExtensionsDataType > ~/Desktop/kextList.txt then press return;
2. Open the kextList.txt file on your desktop > Press Apple(Command) + F to initiate search;
3. In the search field, type "Obtained from: Not Signed" and copy the paths of the unsigned .kext files to a list for later use;
4. Click Next to go through all occurrences, e.g., /System/Library/Extensions/JMicronATA.kext
5. Navigate to /System/Library/Extensions on your drive and delete all unsigned kext files;
6. Restart your Mac, and the boot issue should be resolved.

Method 4: Reinstall macOS High Sierra to fix the Mac not booting issue

The last method you can try is to download macOS High Sierra and create a new bootable drive to do a clean install of macOS High Sierra on your Mac, so it can boot up normally and run smoothly again.

1. Connect the USB bootable drive to your Mac and restart it while holding down the Option key until you hear the reboot sound; 2. From the list of drives displayed on the screen, select the one labeled 'Install macOS High Sierra'; 3. After the USB drive boots up, choose Disk Utility > Select your Mac's startup disk from the list > Click on Erase; 4. Once the Mac's startup disk has been formatted, go back to the Utilities window and select Install macOS > Choose to erase the startup drive for the installation > Follow the on-screen instructions to finish the installation process.

This may take you a few hours to complete the task. And of course, if you have important data, follow Step 1 to extract all saved data first.