I had a need to rebuild an old iMac with macOS Sierra. That in itself was a challenge to try and get a hold of the
Install macOS Sierra.app file as Apple no longer host it, but, I did manage to get a hold of the
InstallOS.dmg which in turn had a
.pkg file gave you the installer.
A short tangent later after then finding a High Sierra VirtualBox image so I could unpack it, I got to the stage of needing to build the USB disk.
Apple’s support doc on this is fine however it took some Google’ing to find the solution to my issue. I tried to run the command as follows…
$ sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app
… but after a few minutes it died with this lovely message:
2021-11-05 14:07:09.635 createinstallmedia[79227:221251] *** Terminating app due to uncaught exception 'NSInternalIncons istencyException', reason: 'Couldn't posix_spawn: error 35' *** First throw call stack: ( 0 CoreFoundation 0x00007fff205811db __exceptionPreprocess + 242 1 libobjc.A.dylib 0x00007fff202bad92 objc_exception_throw + 48 2 Foundation 0x00007fff21317a51 -[NSConcreteTask launchWithDictionary:error:] + 4990 3 Foundation 0x00007fff2133dc29 +[NSTask launchedTaskWithLaunchPath:arguments:] + 146 4 createinstallmedia 0x0000000104ed3968 createinstallmedia + 6504 5 libdyld.dylib 0x00007fff2042af3d start + 1 6 ??? 0x0000000000000005 0x0 + 5 ) libc++abi: terminating with uncaught exception of type NSException /Volumes/MyVolume is not a valid volume mount point.
Again, back to Google and I came across this article which fixed the problem!
The magic line of code:
$ sudo plutil -replace CFBundleShortVersionString -string "12.6.03" /Applications/Install\ macOS\ Sierra.app/Contents/Info.plist
With that run, you can then go back to creating the installer as normal:
$ sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app Ready to start. To continue we need to erase the disk at /Volumes/MyVolume. If you wish to continue type (Y) then press return: y Erasing Disk: 0%... 10%... 20%... 30%...100%... Copying installer files to disk... Copy complete. Making disk bootable... Copying boot files... Copy complete. Done.