Prohibitory Sign When Updating Mac OS and How to Fix it.

Yesterday, January 21st, I finally decided to update my High Sierra to 10.13.2

After downloaded it from App Store, like always the system need to restart to complete the installation.

But I got the prohibitory sign and the system won’t finish it. I tried to reboot my macbook, but still got the same sign. Maybe this is the reason why I don’t want to upadate my OS recently. Lucky me, before I updated it, I have my time machine back up.

Got this symbol and won’t be finish

According to many article on the internet, prohibitory sign on your mac is the sign that your OS can not select the partition of your disk properly or our system couldn’t  find a valid system folder to start up from.

I think this happened to me because I used two partitions on my macbook, so High Sierra got confuse to select the disk, maybe.

The first time I upgrated to High Sierra before, it also didn’t want to install and forced me to erase my 3rd partition on my mac which Windows installed in it.

How to fix your mac if you run into prohibitory sign? This is what I’ve tried for my problem.

  1. Enter to Disk Utility

I tried to enter to disk utility by shutting down my mac, restarting it and hold down the Cmd + R before booting. Then run repair disk permission to fix the disk. And then restarting my mac again. But it didn’t work for me.

  1. Reset PRAM

I tried to reset PRAM by holding option-cmd-P-R before booting up, but it also didn’t work for me.

  1. Reinstall the OS

The last thing I have to try is reinstall the OS. If you have USB bootable, you can reinstall it from it. Or if you don’t have it you can download it form App Store from another mac.

I have a bootable USB and I also can run mac from my external hardisk or from my first partition of internal hardisk. Bacause my bootable USB was installed by another version of High Sierra (10.13), so I choosed to download the latest version of High Sierra from App Store. I entered the mac OS from my external hardisk and started to download it. After that, I installed it to my internal hardisk to the partition that running High Sierra before. Followed the installation process and wait.

From my case, after I installed it and log in to my desktop again, I didn’t need to do anything more, my system and all of the files just back to the last time I was logged in. It supprisingly magic, I think that I have to run migration assistant from time machine backup after the installation complete, but it was not. So I think if you have the same problem like me and the other way can not solve your system, just download the latest version of the new OS and reinstall it.

I hope I share the good information for you guys according to my case. Thank you.


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