"I upgraded my iMac into latest macOS High Sierra last night. And when I completed the update process, tried to start the computer. It won't boot.
If your Mac won't turn on, try these steps: Press the power button for 10 seconds to discharge any residual power. Then, press and hold the power button for 10 seconds to discharge it again. Next, plug in the power cord and press the power button to see if it turns on."
Mac hard drive boot failure is a common issue, especially after a macOS High Sierra update or installation. If your Mac won't boot, don't worry - this article will guide you through a quick fix. You can try one of the methods offered to get your Mac back up and running again.
If your Mac won't boot after a system update, try resetting the System Management Controller (SMC) to resolve the issue, as improperly connected cables or other hardware problems may be preventing it from booting normally.
1. Shut down Mac computer and unplug all cables;
2. Wait for a few minutes and then plug the cables back;
3. If you're unable to enter the system on your Mac, try restarting it.
1. Press and hold the Power button for a few minutes until your Mac turns off.
2. Turn on your Mac and wait a few seconds before pressing the Power button to turn it on.
3. To reset the NVRAM on a Mac, press and hold the Command (⌘) + Option (⌥) + P + R keys simultaneously as soon as you turn on your Mac. This will reset the NVRAM, which can resolve issues with the startup disk, boot order, and other system settings.
4. Rebooting your computer is a good troubleshooting step, but it's unlikely to resolve the issue of your computer not recognizing the USB drive. The problem is likely related to the USB drive itself, the USB port on your computer, or the operating system.
Note: If these two quick fixes didn't help, continue with below complete solutions to get your problem resolved now.
If your Mac won't boot, it's a good idea to restore your important data from a backup before attempting to fix the issue, to prevent any potential loss of valuable files.
If your Mac computer fails to boot, you can use professional Mac data recovery software with a bootable disk to effectively restore your data. You can purchase Deep Data Recovery for Mac with Bootable Media, which allows you to create a bootable media and apply it to restore data from a fail to boot Mac computer.
1. Insert the created bootable media into the Mac and turn it on, immediately press and hold the Option key and select Deep Data Recovery for Mac to boot from it.
2. Connect an external storage device to a Mac computer;
When Deep Data Recovery for Mac launches, follow this tutorial to restore lost files on Mac.
Method 1. Boot Mac from Safe Mode to fix Mac won't boot issue
1. To boot your Mac in safe mode, start by turning it on, then press the Shift key as soon as you hear the startup sound. Hold the Shift key down until you see the Apple logo on the screen.
2. After Mac fully starts, restart the computer normally without holding any keys/buttons.
3. Wait patiently till Mac computer finish the reboot process.
Method 2. Use Disk Utility to restore Mac from Recovery Mode when macOS High Sierra won't boot
1. To boot your Mac in recovery mode, press the power button and immediately hold down the Command + R keys. This will take you to the macOS Utilities window, where you can select an option to reinstall macOS, restore from a Time Machine backup, or run a disk utility.
2. To resolve the issue, click on the Disk Utility option, then select First Aid, and attempt to repair the Mac's disk.
3. Disk Utility will automatically run a file system check (fsck) operation to help repair the macOS High Sierra boot failure.
4. If this fails, try restore from Recovery mode.
5. To reinstall OS X in Recovery Mode, your Mac will automatically download and install the latest macOS High Sierra.
Method 3. Run Terminal to repair Mac hard drive won't boot error due to High Sierra update
1. Open Terminal > Applications > Utilities;
Enter: system_profile SPExtensionsDataType > ~/Desktop/kextList.txt and hit return;
2. To open the kextList.txt file on the desktop, press Apple(Command) + F to bring up the "Find" feature, and then type "kextList.txt" in the search bar to locate and open the file.
3. In the find field, insert "Obtained from: Not Signed" and copy the destination to the .kext file to a list for use later.
4. The user is being asked to cycle through a list of items, specifically kext files in the /System/Library/Extensions directory, by clicking the "Next" button. The example given is the JMicronATA.kext file.
5. Browse your drive to /System/Library/Extensions and remove all unsigned kext files;
6. Reboot and your Mac boot problem shall be all set.
Method 4. Reinstall macOS High Sierra to resolve Mac won't boot issue
If your Mac computer is not booting up normally and working smoothly, you can try downloading macOS High Sierra and creating a new bootable drive to clean install the operating system. This can help restore your Mac to its original state and resolve any issues that may be causing it to malfunction.
1. Connect a USB bootable drive to your Mac, then restart the Mac while holding down the Option key until you hear the reboot tone. This will allow you to boot from the USB drive instead of the Mac's internal storage.
2. To begin the installation process, select the disk called "Install macOS High Sierra" in the drive list that appears on screen. This will initiate the installation of the operating system on the chosen drive.
3. Once the USB drive is booted, select Disk Utility, choose Mac's startup from the list, and click Erase.
4. Once Mac's startup disk is formatted, go back to the Utilities window and select Install macOS, then choose "Erase Startup Drive" to install macOS, and follow the on-screen prompts to complete the installation.
You may need to spend a few hours completing this task. Before proceeding, make sure to save any important data as you'll want to back it up first.