I have no experience whatsoever with macOS (Linux user).
I got an old mid 2012 13" MacBook Pro, which was running OS X Mountain Lion 10.8.5. I tried to upgrade it to macOS Mojave, by launching Mac App Store, and searching for Mojave. After some time, the process stopped with the message "requested range not satisfiable".
Now I am lost between the Mountain Lion world and the Mojave world, because:
About this Mac says Version 10.8.5. I also can't install e.g., Xcode because the OS is too old.
The Mac App Store says that the Mojave upgrade is installed, hence the install button is disabled.
How can I properly upgrade to macOS Mojave? Restarting the device does not change anything.
I want to develop and publish iOS apps, so I require a recent version of macOS.
I installed El Capitan, Sierra and then High Sierra (yes, one after the other; it takes several hours). It was quite difficult to find these updates as the App Store-Search does not show them. I had to google it, find the Apple-page which contained a link (under 4. Download macOS XXX) which is opened in the App Store. from there on, updating worked.
Now I have High Sierra, but I'm still not able to update to Mojave. I get the same error ("requested range not satisfiable").
I think I know the problem. When I try to create a bootable installer (
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume), it says
To use this tool, you must download the macOS installer application on a Mac with 10.12.5 or later, or El Capitan 10.11.6. [...]
Ok, I have downloaded the Mojave installer when the OS was still Mountain Lion, so I understand that message. Problem was that I could not "re-download" it. I had to delete the
/Applications/Install macOS Mojave.app/ -directory by hand. Renaming or moving to a different place was not sufficient. After that, I could start the Mojave-Download in the App Store as expected. The installation was successful after all.