Mac I Had to replace the HDD(mid 2012 model) in a MacBook Pro as when the MacBook booted up it came up with a prohibited sign and even after wiping that HDD and repairing it etc it wouldn’t install the OS through internet recovery. Reinstalling OS X System Software on a Mac with Recovery Mode. It’s a good idea to back up the Mac with Time Machine before beginning this process. Even though this method aims to only reinstall OS X system software on the Mac, things could still go wrong and it’s always better to lean on the side of caution and make file backups beforehand.
An installation error occurs sometimes for when upgrading from OS X Snow Leopard to OS X Lion “Can’t download the additional components needed to install Mac OS X” – Check your network configuration as the install needs to pull down software over the internet.
But the network configuration is OK.!
Check that Software Update can connect directly to Apple Software Update Servers not a custom internal one, remove any Managed Preferences if it is a managed host.
Option 1
![A Required Download Is Missing Mac Os X A Required Download Is Missing Mac Os X](https://docs.unity3d.com/uploads/Main/DeployingUnityOffline-DownloadAssistant.png)
If that still doesn’t get rid of the message I have found on a device that the drive needed to be reformatted – the only thing different about the drive I was trying to install to was that it had a Boot Camp partition on it The Boot Camp partition might be a red herring but certainly reformatting the disk solved the issue.
So:
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![Mac os 10.14 download Mac os 10.14 download](https://i.ebayimg.com/images/g/IswAAOSw7oleIAOQ/s-l300.jpg)
- clone the main HD drive to an external disk use CCC – link below
- boot from the external
- erase/reformat the main HD – use HFS Extended Journaled
- clone back the main HD from the external
- reboot from the main drive
- run the installation upgrade again
This time – no problems.
If you don’t care whats on the disk just erase it and run the upgrade, I wanted to keep all the data intact in my example, hence the clone back.
Cloning courtesy of the fantastic bombastic CCC.
Option 2
A Required Download Is Missing Mac Os X 10.10
Another potential solution is to remove any RAM over 4GB run the install and then put the additional RAM back in after – even then try and limit the RAM slots to one, so not 2GB in each – rather 1 slot with 4GB.