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.

1 Comment

  1. SOLVED: MacBook Will Not Start Up After macOS Update

    I have a MacBook pro running MacOS Mojave.
    For the past year or so, every time a new MacOS update rolls out, and is attempted to be installed on my MacBook, it ends up displaying the circle slash (Prohibitory Symbol). Rebooting still produces a prohibitory symbol. I’m still able to boot into recovery mode (CTRL-R at Startup), however running disk repair on my MacBook HD does NOT solve the problem. I have also tried: (a) specifying the startup disk (problem still persists); (b) attempting to start in safe mode (problem persists); doing the NVRAM reset (problem persists). In the past, the only way i was able to get around the problem, is by re-formatting my HD, installing latest version of Mojave OS, and then migrating all my data from my TimeMachine backup.

    This happened again the other day with the recent Mojave update 10.14.2.
    My computer automatically installed the update overnight, and in the morning, my screen was showing circle slash. This time i did some more research, and discovered that the issue may be caused by UNSIGNED KERNEL EXTENSION (KEXT) files existing on my HD.

    Kernel Extension is a piece of code that extends the capability of the base kernel of an operating system. The kernel typically manages I/O requests, and in OS X, the file ends in “.kext.”

    Starting with Yosemite, kernel extensions must be code signed by the developer with Apple authorization or OS X won’t load them. Sometimes these un-signed kernel extensions cause this headache after an OS X or macOS update.


    After I removed the following KEXT files from the /Volumes//Library/Extensions/ directory, my MacBook booted up properly, and finished installing the Mojave update.

    (note: this is DIFFERENT directory from /System/Library/Extensions/)

    BJUSBLoad.kext (Creator: Canon)
    CIJUSBLoad.kext (Creator: Canon)
    ParagonSnapshot.kext (Creator: Paragon)
    ufsd_NTFS.kext (Creator: Paragon)
    VDMounter.kext (Creator: Paragon)
    LittleSnitch.kext (Creator: LittleSnitch)

    Note: When I removed these KEXT Extensions, the “circle slash” problem did not resolve until i finally removed: ParagonSnapshot.kext and VDMounter.kext

    Below is a link to a useful article which provides some helpful information regarding:
    MacBook Will Not Start Up After macOS Update, How-To Fix
    In that article, the section titled “Un-Assigned Kernel Misfiring” explains how to boot into recovery mode and launch Terminal utility. However, one problem with that article is that the kextstat command is not available in Terminal utility running in recovery mode.

    As a work-around, these are the steps i took to solve the problem:
    1. Boot to Recovery (with CMD + R or CMD + Shift + R if you don’t have recovery partition)
    2. First, pick Disk Utility, select your main disk and Mount it; this is required if your disk is encrypted and requires password to be mounted
    3. Now select Disk Utility -> Quit; then Utilities -> Terminal
    4. Begin typing in Terminal following commands:
    4a. cd /Volumes/
    4b. cd
    (Note: If your system drive has any spaces in it’s name, then put the name in single quotes. For example, my MacBook boot drive is called “MacBook HD”, so the command I would type is: cd ‘MacBook HD’
    4c. cd library
    4d. cd extensions
    4e. ls
    (Note: first letter is a lower case L)
    After you type ‘ls’, you should see a list of KEXT extensions like this:
    ACS6x.kext CIJUSBLoad.kext
    ATTOCelerityFC8.kext CalDigitHDProDrv.kext
    ATTOExpressSASHBA2.kext HighPointIOP.kext
    ATTOExpressSASRAID2.kext HighPointRR.kext
    ArcMSR.kext PromiseSTEX.kext
    BJUSBLoad.kext SoftRAID.kext

    The KEXT extensions listed above are all ones properly signed by Apple.
    These KEXT extensions can remain, but if you have other KEXT extensions listed, chances are that some or all of those others are causing the issue.

    If you see any of these extensions (listed below), you should be able to safely delete them in order to fix your problem. I’d recommend removing each extension, one at a time, then rebooting to see if it worked, and if not, repeat steps above and delete next one. Based on my limited research, the ones i’d recommend deleting first are:
    ParagonSnapshot.kext (Creator: Paragon)
    VDMounter.kext (Creator: Paragon)
    LittleSnitch.kext (Creator: LittleSnitch)
    ufsd_NTFS.kext (Creator: Paragon)

    While in Terminal utility (in Recovery mode), to delete (or remove) a desired KEXT extension (eg., LittleSnitch.kext) type:
    rm -r
    (eg, “rm -r LittleSnitch.kext”)

    9. quit the terminal and restart

    Hope this helps! 🙂
    Good luck!!

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