I tried to install the app 'Duet Display' today. It was always troublesome on my Windows PC, so I was disappointed to see it wasn't working very well on my new MBP 2017 13" w/ TB as well. The installer ran fine, but upon reboot the progress bar seemed to hang. I never reached the login prompt. A macOS update was pending and was waiting for a reboot, my iPad was plugged in and the MBP was on charge.

Anyway, I proceeded to contact Duet's support email, with them telling me to boot into Safe Mode (so I can delete the file duetdisplay.kext from /Library/Extensions), but my Mac won't even boot to Safe Mode; it seems to hang again. I never reached the login prompt, again. I'm thinking that reinstalling might be my only option, or removing the file manually via the Terminal in Recovery.

What are my options?

  • Deleting the files (at least, I thought I did!) didn't work, reinstalling macOS did. Interestingly, Duet remained on the system and worked well. Hmm... Jan 26, 2018 at 10:50

4 Answers 4


I've just encountered the same problem on my 15" 2016 MacBook Pro running macOS 10.14.2 Mojave. While I expected it to take some time starting up it never came back to the login screen and here's how I solved the problem:

  1. Reboot into single user mode by pressing the cmd + s keys on startup. Note this not safe mode, it's single user mode.
  2. Once in single user mode type mount -uw / so that you get write access to the drive.
  3. Navigate to the kexts directory with cd /Library/Extentions.
  4. Now delete the Duet Display kexts with sudo rm -Rf DuetDisplay.kext, it's a directory thus the -Rf.
  5. Next clear caches with sudo rm -Rf /System/Library/Caches/*.
  6. Finally restart with shutdown -r now.

Hopefully that helps anyone else with this issue. I'm so disappointed in Duet Display and asking for my money back. It's cost me more in loss of productivity fixing this mess than I hoped to gain using their App.

  • Thanks for the answer. I can't confirm that this works because I don't use Duet anymore, but I hope this helps anyone who still does. Feb 17, 2019 at 10:33

I had the same problem you described above. I was so happy that I found this post, because I almost decided to reinstall my MacbookPro (mid 2018).

But I tried it again because I really wanted to use duet. And the second time I installed it, it worked perfectly!

I had downloaded the latest version ( When you install it duet asked you to add it to your security. ignore that message en quit the duet app trough activity manager.

Open you security and privacy setting in you settings en unlock the settings with the lock left below. Go to you Privacy tab and open duet again. On that moment duet asks again to added to your security. in the accessibility you will see the duet app logo. enable it in your privacy. Then you can restart you mac and this time it will not hang on the loader!

I hope this will also work for you. I am using duet happily ^^

  • Thanks for your feedback. I'm glad this post has helped people; I haven't bothered using Duet for so long. Feb 17, 2019 at 10:32

Just want to add a few things since Mojave and Recovery are substantially different than the old single user mode:

  • Mac with T2 chips you can’t do Ctrl+S anymore. Go into Recovery mode thru Ctrl+R instead. This changes the mount point for the filesystem you intend to modify, so be careful with what you remove / change.

  • when looking thru Library and System folder, make sure you go /Volume/Macintosh HD/ instead of looking at the Library and System folder of the virtual disk instead.

  • consider making sure your backup is ready to be used in case you make things worse following this or other directions.

  • Thanks! This is great additional information. Aug 25, 2020 at 20:01
  1. Reboot while holding Command-R to bring up the recovery mode
  2. Open disk utility from the window that appears, click on the main hard disk and press the "mount" button. If it asks for a password the users login password will work.
  3. Exit disk utility
  4. Open Terminal from the "Utilities" menu bar item
  5. Type: cd /Volumes
  6. Type: ls
  7. A list of hard disk volumes will be displayed, unless renamed there is most likely one named "Macintosh HD", if it was renamed by the user it will be whatever name they named it, and should expect to see.
  8. Type (with whatever the main volume is named inside the quotes): cd "Macintosh HD"
  9. Type: rm -rf Library/Extensions/DuetDisplay.kext
  10. Type: rm -rf Library/StagedExtensions/Library/Extensions/DuetDisplay.kext
  11. Quit terminal, and quit "macOS Utilities", selecting choosing to reboot.

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