Can't boot up your Mac after upgrading your OS? Are you facing a kernel panic error? Don't worry, here's how you can fix it! 1. Boot up your Mac by pressing on the power button. 2. Hold down the Command (⌘) + Option (⌥) + R combination immediately upon hearing the startup chime. 3. Hold the keys until the animated globe appears on the screen. 4. In the next step, a Wi-Fi menu appears. Select your Wi-Fi network and enter your password. (If you’re using Ethernet, you don’t have to connect to a Wi-Fi). 5. Once connected to a Wi-Fi, it’ll download the recovery tools from Apple’s servers. 6. Depending on your Internet connection, this may take from a couple of minutes to up to an hour or longer. 7. If all goes well, you’ll be presented with the macOS Utilities window. 8. There are 2 options from here. a) Erase HD and restore files from Time Machine b) Clean install OS (All files will be deleted) Time Machine Restore 1. Now if you have your files backed up with Time Machine you can try restoring your files. 2. Select "Disk Utility". 3. Select the corrupted Hard Drive and navigate to the "Erase" tab. 4. Select "Mac OS Extended (Journaled) for the format. 5. Enter the name of your Hard Drive and select "Erase". (WARNING: This will permanently delete all of your files.) 6. Once you've erased your Hard Drive, back out and select "Restore From Time Machine Backup" 7. Now select your backup USB / External Drive source. 8. Select the backup you want to restore from. 9. Select the Hard Drive you just erased and restore it. 10. And finally, select "Continue". 11. Now just wait until it restores your backup! 12. Congratulations, you just saved your files and Mac! Clean OS Format Install 1. Now if you don't have a Time Machine backup, the only way to fix your Mac is by reinstalling the factory OS. (This will permanently delete all of your files). 2. Select "Reinstall OS X" 3. The factory (default) OS will be installed on your Mac. 4. Press "Continue". It will verify your Mac's eligibility with Apple. 5. Press "Agree" 6. Choose your Hard Drive and select "Install". 7. It will now start downloading additional components. 8. Your Mac will restart and the installation process will begin. 9. Be very patient. This may take a while. 10. Once you see the "Welcome" screen, set up your Mac. 11. Choose your keyboard layout. 12. Select your Wi-Fi network. 13. Transfer information (We prefer skipping) 14. Sign into your Apple ID (We prefer skipping) 15. Read the terms & conditions and select "Agree". 16. Create your account. 17. Setup your diagnostics and usage (We prefer skipping) 18. Congratulation, you've fixed your Mac. Mac: How To Fix A Kernel Panic / OS Upgrade Startup Boot Error (2018)