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Unable to make bootable USB drive

I am trying to make a Sierra Bootable USB stick with Terminal and I keep getting this error message : Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Couldn't posix_spawn: error 35"

I have tried various USB drives, computers and methods, nothing works. Is there a solution?

iMac 21.5", macOS 10.13

Posted on May 23, 2020 4:58 PM

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Question marked as Best reply

Posted on May 23, 2020 10:41 PM

There is problem with making a bootable USB stick installer, been like that for 7 months now and Apple seem reluctant to do anything about it.

Usually the error reported is that Volumes/<USBName> is an invalid mount point, your error is different.


Have you downloaded the most recent version of Sierra available from here,

How to upgrade to macOS Sierra - Apple Support

at Section 4 you download InstallOS.dmg which you open to InstallOS.pkg.

Double-clicking on the InstallOS.pkg will open an installation window, this does not

install Sierra but creates Install macOS Sierra.app in your Applications folder.


With Install macOS Sierra.app in the Applications folder open Terminal and copy and paste this


 sudo plutil -replace CFBundleShortVersionString -string "12.6.03" /Applications/Install\ macOS\ Sierra.app/Contents/Info.plist


press Return

enter your password

press Return


now enter the createinstallmedia command for Sierra in Terminal (MyVolume is Apples default name for a USB but you can enter the name of your USB in there.


sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app 


press Return and follow the prompts.


If you still end up with an error can you post a screenshot of your Terminal window.

6 replies
Question marked as Best reply

May 23, 2020 10:41 PM in response to Craig Gray

There is problem with making a bootable USB stick installer, been like that for 7 months now and Apple seem reluctant to do anything about it.

Usually the error reported is that Volumes/<USBName> is an invalid mount point, your error is different.


Have you downloaded the most recent version of Sierra available from here,

How to upgrade to macOS Sierra - Apple Support

at Section 4 you download InstallOS.dmg which you open to InstallOS.pkg.

Double-clicking on the InstallOS.pkg will open an installation window, this does not

install Sierra but creates Install macOS Sierra.app in your Applications folder.


With Install macOS Sierra.app in the Applications folder open Terminal and copy and paste this


 sudo plutil -replace CFBundleShortVersionString -string "12.6.03" /Applications/Install\ macOS\ Sierra.app/Contents/Info.plist


press Return

enter your password

press Return


now enter the createinstallmedia command for Sierra in Terminal (MyVolume is Apples default name for a USB but you can enter the name of your USB in there.


sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app 


press Return and follow the prompts.


If you still end up with an error can you post a screenshot of your Terminal window.

Unable to make bootable USB drive

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