OS X Mountain Lion (version 10.8) is the ninth major release of macOS, Apple Inc.' S desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012 for purchase and download through Apple's Mac App Store, as part of a switch to releasing OS X versions online and every year, rather than every two years or so. MacOS Big Sur elevates the most advanced desktop operating system in the world to a new level of power and beauty. Experience Mac to the fullest with a refined new design. Enjoy the biggest Safari update ever. Discover new features for Maps and Messages. And get even more transparency around your privacy. If you’re using macOS Mojave or later, choose Apple menu System Preferences, then click Software Update. If you’re using an earlier macOS, use the App Store instead. Learn how to download and install macOS Big Sur Go to the App Store. If your Mac is using an earlier version of any Mac operating system, you should install the latest Apple software updates, which can include important security updates and updates for the apps that are installed by macOS, such as Safari, Books, Messages, Mail, Music, Calendar, and Photos.

Upgrade to macOS Big Sur

Before installing this upgrade, make sure that your Mac is ready.

Check compatibility

macOS Big Sur supports most Mac models introduced in 2013 and later.

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Make a backup

Before you upgrade, make a complete backup with Time Machine, or store your files in iCloud.

Learn how to back up your Mac

Free up space

If the installer needs more storage space to upgrade, you can free up space using tools that come with your Mac.

Free up storage space

Download macOS Big Sur

If you’re using macOS Mojave or later, choose Apple menu  > System Preferences, then click Software Update. If you’re using an earlier macOS, use the App Store instead.

Learn how to download and install macOS Big SurGo to the App Store

Get to know macOS Big Sur

Learn about some of the new features of macOS Big Sur.

Control Center

Control Center brings favorite controls such as Bluetooth, Wi-Fi, Do Not Disturb, and Sound together in a single place—so you can easily adjust them at any time.

Use Control Center

Notification Center

Notification Center puts notifications and>

Safari

Customize your start page, navigate with ease using the new tab bar, and access a new privacy report to see just how Safari protects your privacy as you browse.

Get to know Safari

Maps

Discover great places around the world and navigate easier with guides, cycling directions, indoor maps, Look Around, electric vehicle routing, and more.

Messages

Send messages to friends and family using new tools that make it easier to keep track of group conversations and give you fun, engaging ways to express yourself.

Use MessagesLearn more on YouTube

Photos

Use the expanded editing capabilities in Photos to easily make simple changes and more advanced adjustments to your photos.

Learn how to edit your photos

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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

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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Upgrade Os X Lion To Mojave Az

• 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.

Upgrade Mac Lion To Mojave

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

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.