OS X Yosemite Splash

Installing Yosemite (or any other) OS X as secondary OS

Just as I’m writing this post, my disk is shrinking once again. Last time it was because of me installing Lion1. First I wanted to use Virtual Box to run it within a virtual machine. After I tried several option to boot install I finally gave it up. My last hope to install Lion was by load (restore) contents of the DMG hidden in the OS X Install app downloaded from Apple Store into a real partition and install.

I was successfull with Lion. This time I’ll keep journal and I try to install Yosemite.


Yosemite Beta Program

Sign up for beta program to download Yosemite, the App Store will fire up your download. Now wait for it to finish and than quit the installer. Continue only if you’re willing to upgrade your current OS to beta directly.

Install OS X Yosemite Beta.app

Open Finder, go to Applications and locate Install OS X Yosemite Beta.app, right click the app icon and select Show Package Contents and locate Contents/SharedSupport/InstallESD.dmg. It’s the actual hard disk image of the OS X installation.

Locate InstallESD.dmg

You can double click the .dmg file to open it in a Disk Utility.

Splitting the HD

OS X Disk Utility

To shrink/partition disk on OS X you need to use Disk Utility hidden in Applications/Utilities subdirectory. Be prepared. The process of partitioning takes a while, more than one hour was my case. I’m suspicious the OS X is defragmenting the drive before it splits partition.

I’ve made a mistake. I forgot to create 2 partitions:

  1. source installation files (call it Untitled);
  2. place to install new OS.

I needed to wait for the partition to finish to start another partition process. But I assume, since there are no files, it would not take that long. (Fingers crossed.) Yes. It took just few seconds.

Partitioning Mackintosh HD for new OS Finished partitioning before installing OS X

Create install media

Follow instructions for creating bootable install volume for Mavericks. I’ve used Terminal and utility createinstallmedia hidden in /Applications/Install\ OS\ X\ Yosemite\ Beta.app/Contents/Resources/. Run in terminal.

<code>sudo /Applications/Install/Install\ OS\ X\ Yosemite\ Beta.app/Contents/Resources/createinstallmedia createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite\ Beta.app  --nointeraction
Erasing Disk: 0%... 10%... 20%... 30%...100%...
Copying installer files to disk...
Copy complete.
Making disk bootable...
Copying boot files...
Copy complete.

The disk will we erased and renamed Install OS X Yosemite Beta.


Restart your Mac and during boot hold option (alt) button.


Everything went as expected, I followed on screen instructions as I’m writing these words, I am doing that on my “shiny new” toy.

Happy installing.

  1. I needed OS X Lion to run simulators of iPhone’s iOS prior to version 7. Since Mavericks, the OS has changed so much, that it’s possible to simulate only iOS 6 and higher. (I chose Lion over Mountain Lion, since it did not yet include Game center and other “inprovements”)