So I'm trying to boot a yosemite installation from an 8GB USB with the dmg file I downloaded from the app store, but once I hit "option" during my mac's startup and choose the correct usb, I get the following error

"Cannot Install Yosemite on the Mac. Yosemite already has been installed"

This is of course false as I have OS X 10.7 and I'm trying to upgrade to 10.10

Any help or ideas?

Update: Per a suggest I've inputed the following code into my terminal:

pkgutil --packages | grep -i base ; uname -a ; sw_vers ; pkgutil --pkg-info  com.apple.pkg.BaseSystemBinaries

Here was the Result:

Darwin *****-*****-MacBook.local 11.4.2 Darwin Kernel Version 11.4.2: Thu Aug 23 16:26:45 PDT 2012; root:xnu-1699.32.7~1/RELEASE_I386 i386
ProductName:    Mac OS X
ProductVersion: 10.7.5
BuildVersion:   11G63
package-id: com.apple.pkg.BaseSystemBinaries
volume: /
location: /
install-time: 1436744136
groups: com.apple.snowleopard-repair-permissions.pkg-group com.apple.FindSystemFiles.pkg-group 

Hopefully this give more insight into my issue.


  • 1
    If you download OS X 10.10 Yosemite from the App Store it's in a application bundle (Install OS X Yosemite.app), not a .dmg file, even though there is an "InstallESD.dmg" within the application bundle, so how did you create the USB Yosemite installer? Did you use the /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia command, as one's supposed to or some other method? Jul 13, 2015 at 1:23
  • 1
    Can you post a screenshot ?
    – Pratik
    Jul 13, 2015 at 2:03
  • Discussion, including a hint:: chat.stackexchange.com/transcript/message/22732451#22732451 Jul 13, 2015 at 6:00

1 Answer 1


Sounds like a fault, or that perhaps there is a conflict. You are trying to upgrade from 10.7 to 10.10 and its possible you either can't do that, or your machine is incompatible. Although I expect it would tell you as such.

In any case, what ever the reason is your only real way forward is to backup with Time Machine if you haven't already onto an external hard drive, and then do a fresh install rather than an upgrade.

After you've done this during the install process you'll be able to import old backups etc... You can use your backup from Time Machine to restore your files on OS X 10.10.

  • 2
    I don't see why this has been down-voted. This is a perfectly factual answer. I'll just up-vote it now. Jul 12, 2015 at 21:53
  • Given the apparent peculiarity of the original data (Lion somehow misinterpreted as Yosemite) I suggest an additional precaution with the completed Time Machine backup of that data. Take the completed backup to a Mac where the installation of Yosemite is known to be good, and then check that data can be selectively restored from the backup. Jul 13, 2015 at 6:06

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