Upgrading an old operating system can cause data loss if interrupted. Follow these preparation and execution steps carefully. Step 1: Back Up Your Data
This guide will direct you to the complete installer DMG.
Press the Power button while holding down the key on your keyboard. Release the key when you see the Startup Manager screen.
Apple keeps older versions of macOS available for users with legacy hardware. Avoid third-party torrent sites or unverified download blogs, as these files can contain malware or be corrupted. The Official Apple Download Method
Before you download and install Mac OS X Yosemite 10.10.5, make sure your Mac meets the following system requirements:
To ensure security and compatibility, it is best to use official Apple sources:
: Always perform a Time Machine backup before an OS upgrade. Running the Installer : Double-click the downloaded InstallMacOSX.dmg .
Getting the full OS as a DMG is harder.