下载完成后，挂载 DMG，运行其中的 .pkg 安装包并按提示操作即可。。

Historically, Apple made it very difficult to download older OS versions. If you search for a direct link today, you will encounter three scenarios:

sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/YosemiteInstaller --applicationpath /Applications/Install\ OS\ X\ Yosemite.app Use code with caution. Type your admin password and press Enter to finish. 3. Install the OS Shut down your Mac. Restart while holding down the key. Select the USB drive from the boot menu. Follow the prompts to complete your installation. Why Choose OS X Yosemite 10.10.5?

The official way to download OS X Yosemite 10.10.5 is through Apple Support

Also, there's the Apple Developer website where developers can access older versions. If the user has access to a developer account (either personal or company), they can download from there. But if they don't have one, that's another hurdle.

| Component | Requirement | | :--- | :--- | | | OS X 10.6.8 (Snow Leopard) or newer | | RAM | 2 GB minimum | | Storage | 8 GB available disk space |

Select the USB drive in the sidebar, click the button, and format it as Mac OS Extended (Journaled) with a name like Untitled .

This comprehensive guide provides the verified direct download links, hardware compatibility requirements, and a step-by-step tutorial to create a bootable installer from the DMG file. Official Mac OS X Yosemite 10.10.5 Download Links

: Open your Applications folder and look for "Install OS X Yosemite." Double-click this to begin the actual upgrade process. Important Legacy Notes

Terminal will erase the flash drive and copy the installer files over. Once finished, you can plug this USB drive into any compatible Mac, hold down the key while booting up, and select the installer drive to perform a clean system setup.

Note: If you use a modern macOS version to download this file, Safari or your browser might warn you about an outdated certificate. You can safely bypass this warning if the URL strictly originates from the official apple.com domain. How to Extract the Installer from the DMG File