I split my macpro disk into 2 partitions. I wish to continue to use partition 1 as a 10.6.8 (Mountain Lion) system. I wish restore everything (O/S, data, etc.) from a Time Machine backup, from a MacBook Pro laptop running Mavericks to my second partition on the MacPro. So I want to end up with a machine that can run either Mountain Lion or Mavericks.

When I rebooted into 10.6.8, I saw the second partition "folder" on the desktop. Now the 2nd partition does not yet have an O/S, but the last thing I expected was to see it on the Mountain Lion desktop!

What is happening here? Why am I seeing the second partition as if it were a part of 10.6.8? Did I fail to partition the drive correctly?

To partition my drive, I booted from the reinstall disk, got into utilities, did not select the route that would erase everything and reinstall the O/S, but selected the route that would preserve the data on the drive and split the single partition into 2 equally sized partitions.

  • Welcome to Ask Different! Your question seems more about the visibility of the other partition than the process of putting a new OS onto it. I'd be tempted to edit the question title to perhaps better reflect that.
    – Tetsujin
    Commented Sep 16, 2015 at 8:09

2 Answers 2


By default, the Mac will always mount all non-hidden partitions - so both partitions will automatically mount to both OSes, whichever you boot from, even when each contains a different OS.

You can set each to not mount when the other OS is 'in charge' by tweaking a file known as fstab in each OS separately; but we'll come to that later...

First thing to ensure is that your two partitions have different, recognisable names - it will save a lot of trouble later.

Then you need to get Mavericks onto the new partition.
On first boot after installation it will ask if you wish to Migrate from another machine. That's your time to feed it the Time Machine backup of your MacBook Pro.
By the time it's finished, your Mavericks partition will be a usable 'copy' of your Macbook.

To determine which it will boot into at any given time, you can set that in System Prefs > Startup Disk. That will set the default OS that it will boot into.
To boot into the other on just a single occasion, hold Alt ⌥ at the startup chimes & choose it from the drive icons that will appear [You may also see Recovery at that point too]

Once you are sure that each will boot when requested, then you can set your fstab file to not mount the other drive in each case.

Changing the fstab file to hide a partition is just a 'simple task' of adding one line of text to a text file; one on each boot partition. This 'simple task' is unfortunately complicated by a couple of factors...
Firstly, because you don't 'own' the file the system will try to stop you from writing to it.
To get around this, we drag the file to the desktop & work on the copy that is made there.
It's also in a hidden location, so it's not easy to get to, so we need to start by making it visible…

Late Edit: Since perhaps High Sierra, you can enable hidden file visibility simply by key command from Finder - Cmd ⌘ Shift ⇧ . (stop/period), thus avoiding all the defaults write below
If you need to use fstab frequently, add yourself to the ACL, which saves having to work on a copy each time

  • Open Terminal [Applications/Utilities]

  • Type
    defaults write com.apple.finder AppleShowAllFiles YES
    & hit Enter [You can copy/paste] Right click the Finder icon in the Dock & select Relaunch. This will make the Finder disappear, then reappear showing all the hidden files [We'll revert this at the end.]

  • In Finder, navigate to *current boot drive*/etc/fstab
    etc is an alias, & the fstab file may or may not exist. If it doesn't we can make a new one.
    Drag fstab to the desktop, it will make a copy. If no fstab file exists, you can just make a new file from Terminal by typing
    touch ~/desktop/fstab
    & one will appear on the desktop.

  • In Terminal - Type
    diskutil info *partition name of other partition*
    & hit Enter
    We are looking for the UUID of the other partition here - the one you want to hide when you are booted into this one, so for instance from Mountain Lion you're looking for
    diskutil info Mavericks HD

  • Find the line that says Volume UUID & copy the long number that looks like this 20F8C09F-9609-39BD-9C47-D82DCC98ECDE [Ignore the one underneath it that looks similar]

  • Open your desktop copy of fstab in TextEdit

  • Add a new line to the fstab file like this, but using your copied UUID -
    UUID=C126C736-1585-3D12-9CF1-F95EFF0CF744 none hfs rw,noauto
    Ignore any existing lines that may be present, just add your new one underneath.

  • Fix the ownership on the new version of fstab by typing
    sudo chown root:wheel ~/desktop/fstab
    Terminal will ask for your password before proceeding.

  • Delete the existing fstab file from etc/ & then drag the new one into place. Password will be required.

  • Repeat that process on the other partition, first by finding its own fstab file, then adding to it the UUID of your current boot partition - so each boot drive will hide the other one.

  • Once completed & satisfied that it actually works, hide the 'invisible' files again -
    defaults write com.apple.finder AppleShowAllFiles NO
    then relaunch the Finder once more.

If you ever need to see the other partition later, you can always mount it manually from Disk Utility.

  • Thanks for the detailed reply. I've run into a problem at the 4th paragraph, getting Mavericks on the new partition. "On first boot after installation..." I went into system preferences, startup disk, and it didn't show the 2nd partition at all. It showed the install DVD, the 10.6.8 original partion harddisk, and a network resource with a question mark inside of its icon. (I do not have a network resource)
    – Needsleep
    Commented Sep 16, 2015 at 21:11
  • Not sure what went wrong, but it sounds like the install just didn't happen - have a look at osxdaily.com/2013/06/15/… & see if it may help... Though you didn't say which Mac Pro it is - the early ones won't take Mavericks without a deal of fiddling...
    – Tetsujin
    Commented Sep 17, 2015 at 17:49
  • I didn't get to installing yet. In paragraph 4 you say,
    – Needsleep
    Commented Sep 21, 2015 at 16:14
  • I didn't get to installing yet. In paragraph 4 you say, "(1) you need to get Mavericks onto the new partition.(2) On first boot after installation it will ask if you wish to Migrate from another machine." And this is where I sit. How do I get my machine to boot into the new partition? In your latest post, you asked which MacPro I own. I have a mid-2010 model - OS X 10.6.8 Snow Leopard single 6-core 3.33 GHz "Westmere" Xeon (W3680) processor.
    – Needsleep
    Commented Sep 21, 2015 at 16:22
  • Did you work through the previous link? You need to get the install to work before any of my post really will make any sense
    – Tetsujin
    Commented Sep 23, 2015 at 17:47

I was part way into the project when I started this thread, but this is a full list of steps.

Steps to partition your Apple MacPro drive:

  1. Boot from the reinstall disk.
  2. Get into utilities.
  3. Be careful here - do not select the route that would erase everything and reinstall the O/S, but instead, select the route that would preserve the data on the drive and split the single partition into two partitions.
  4. Make sure you name the new partition with a different name than your original partition. (Comes up as a new disk.)
  5. If the new O/S is the current offering from Apple, get online and download the installer. Install onto your new partition. (This was not the case for me, so I have no idea how to instruct you in this.) Continue with step 8.
  6. If the new O/S is not the current Apple offering, get yourself an appointment at your local Apple Store's Genius Bar.
  7. Have them add the installer to your new partition.
  8. Set the boot drive to your new partition. (If you executed steps 6 & 7, have the Genius Bar tech set your boot drive for you. If your last step was step 5, get into System Preferences, Startup Disk and set it yourself and then power down your Mac.)
  9. Once back at home, with the machine off, attach the Time Machine backup drive to the Mac and turn it on. Wait for it to settle (10? seconds)
  10. Power up the Mac.
  11. Work through the screens, selecting Time Machine as the source drive. I believe this comes up as an icon only - looks something like, Time Machine Icon
  12. Note: Since you set the startup disk, you won't be asked for a destination drive - it assumes your destination -is- the startup disk.

We only had O/S and Applications on our backup (no data), so the restore to the new drive took a mere 35 minutes. The tech at the Apple Store said more typical times to restore would be on the order of a couple of hours.

A huge thank you goes out to Tetsujin who was instrumental in helping me understand my remaining steps.

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