Stuck in Yosemite with OS X Installer Drive and a Missing OS X Mavericks Partition? Here’s the Fix
Some Mac users who partitioned their Macs to dual boot between the beta OS X Yosemite builds and stable OS X Mavericks releases have discovered a disconcerting issue; their Mavericks partition seems to have vanished and been replaced by an “OS X Installer” partition, forcing them to be stuck in OS X Yosemite. The obvious concern is that data loss occurred, but assuming you didn’t accidentally format the Mavericks drive, it has not, instead, the volume is just temporarily missing, having been taken over by the Yosemite Installer.
To clarify the problem description, it’s fairly easily identified: after partitioning a Mac for dual booting between OS X Yosemite and Mavericks, a user reboots with the Option key to bring up a few partitions; the Yosemite drive, a Recovery HD drive, and a “OS X Installer” partition… but no Mavericks partition is available or visible. Not to worry, the drive is still there, and there are two simple solutions if you run into the missing OS X Mavericks partition, use whichever is appropriate for your situation:
Restore & Boot Into Missing Mavericks Partition from Yosemite During Mac System Reboot
- Reboot the Mac
- Hold down Command+R to boot into Recovery Mode
- Go to the Apple menu and choose “Startup Disk”
- Select the “OS X Mavericks” partition to boot into (the version number of OS X will be listed), choose “Continue” and “Restart” to boot into Mavericks
That’s it, you’re back in Mavericks. Now you can reboot and dual boot between Yosemite and Mavericks as usual with the Option key, or by continuing to go through the Startup Disk menu within either version of OS X, which we’ll describe next;
Returning to OS X Mavericks While Booted in OS X Yosemite (or Vice Versa)
- Go to Apple menu and then to System Preferences
- Head to “Startup Disk”
- Select the appropriate “OS X Mavericks” partition from the drive list as the new default startup volume
- Whenever appropriate, restart the Mac and you’ll boot back into Mavericks (or Yosemite, if selected)
Again, rebooting the Mac will now go into the volume you chose, whether Yosemite or Mavericks. Or you can use the Option key on boot to get the startup disk selection upon restart. Thanks to Phil for pointing this solution out in our comments!
With whatever method, you should only need to do this action once to restore the “OS X Installer” partition to become the expected Mavericks “Macintosh HD” (or whatever your drive is named) partition. Again, after this has been completed, you can now regularly dual boot between OS X Yosemite and OS X Mavericks on their respective partitions as originally intended.
This issue seems to occur somewhat randomly and has not impacted all users, but it can happen whether Yosemite was installed from a USB boot drive or directly from the downloaded installer from the Applications folder. Obviously a bug, and that sort of thing comes with the territory given the OS X Yosemite Beta and Developer Preview builds are not final release software. Fortunately it’s easily resolved, so if you happen to encounter this issue, just rely on Startup Disk to quickly fix it.
Find any other bugs or inconveniences with the beta build? Don’t forget to send feedback about Yosemite to help shape the future of OS X.