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OS X Base System only disk available

Hi! I had problems with my iMac and tried to erase the OS and re-install, but I did something wrong and now all I have is asingle partition with OS X Base System that is the size of my HD (1 TB), see picture 1. This new disk image cannot be partitioned: when I hit the + sign in the partition screen, nothing happens. In the Disk Utility, the options for erase, restore and unmount are all unavailable (see picture 2), I imagine that's because you normally cannot do any of these on the OS X Base System disk. This disk is also locked, so I cannot re-install High Sierra (see picture 3).


As the OS X Base System is the only thing left in the computer, every time I start it up, it does directly into the Recovery menu.


I've researched on the internet and a lot of people made this mistake. Most of them where able to either erase or re-install the system, but I'm at a dead end, as I don't have any of these options available. I don't know what else to try. Does anyone know how to fix this? Thanks!


User uploaded file
Pic 1 - OS X Base System is the only disk available


User uploaded file
Pic 2 - When I press the + sign nothing happens


User uploaded file

Pic 3 - Cannot reinstall High Sierra as the only disk available is OS X Base System, that is locked

iMac, macOS High Sierra (10.13.3), null

Posted on Feb 9, 2018 9:13 AM

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Posted on Feb 9, 2018 2:02 PM

Yes. When selecting that first entry (called APPLE HDD ST1000LM024 Media) and going into the Partition option, what I see is what I've posted on Picture 2 of the original post: pressing the + sign to create a new partition doesn't work and it shows that the only partition available is the OS X Base System, that is the size of the HD (1 TB). Also, when selecting it, the options Erase, Restore and Unmount are not available.

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Feb 9, 2018 2:02 PM in response to Csound1

Yes. When selecting that first entry (called APPLE HDD ST1000LM024 Media) and going into the Partition option, what I see is what I've posted on Picture 2 of the original post: pressing the + sign to create a new partition doesn't work and it shows that the only partition available is the OS X Base System, that is the size of the HD (1 TB). Also, when selecting it, the options Erase, Restore and Unmount are not available.

May 2, 2018 12:25 AM in response to Kappy

Genius!!!! After searching for help, the Mac finally worked with your step by step instructions!!!! Thank you sooooooo much!!!


To those stuck at the reboot and unable to install, the most important step was the comm-option-r and hold it. Had been doing comm-r and was stuck in the failed heart/brain-painful/frustrating loop.


Follow the step by step given earlier by kappy.. the Mac will reinstall.. which will like another 30 minutes.


Thank you again. It works!!!


Critical step::::;

1. To install the version of OS X that was currently installed use Command-Option-R

.

2. To install the original factory version when the computer was new use Command-Option-Shift-R

.

Feb 9, 2018 1:21 PM in response to marcia.marchiori

Do this:

  1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
  2. Select Disk Utility from the Utility Menu and click on Continue button.
  3. When Disk Utility loads select the topmost (out-dented entry, usually disk ID and maker) from the Device list.
  4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
  5. Set the Format type to APFS for an SSD or Mac OS Extended (Journaled) for an HDD.
  6. Click on the Apply button, then wait for the Done button to activate and click on it.
  7. Quit Disk Utility and return to the Utility Menu.
  8. Select Install OS X and click on the Continue button.

Feb 9, 2018 8:07 PM in response to Csound1

Internet Recovery for Qualified Mac Models


  1. Restart the computer. Immediately after the chime hold down the (see Note below) keys until a globe appears.
  2. The Utility Menu will appear in from 5-20 minutes. Be patient.
  3. Select Disk Utility and click on the Continue button.
  4. When Disk Utility loads select the drive (usually, the out-dented entry) from the side list.
  5. Click on the Erase tab in Disk Utility's main window. A panel will drop down.
  6. Set the partition scheme to GUID.
  7. Set the Format type to Mac OS Extended (Journaled.)
  8. Click on the Apply button, then click on the Done button when it activates.
  9. Quit Disk Utility and return to the Utility Menu.
  10. Select Reinstall OS X and click on the Continue button.


Note:

1. To install the version of OS X that was currently installed use Command-Option-R.

2. To install the original factory version when the computer was new use Command-Option-Shift-R.

Feb 10, 2018 12:49 PM in response to Csound1

You jumped in with your replies to the OP and stepping over an already ongoing discussion. I answered replies I saw directed towards me. However, at the end, I sent out a reply that I see went to you instead of the OP. I reckon I clicked the wrong "Reply" button. Honestly, I didn't pay any attention to what you were posting.

Feb 9, 2018 11:12 AM in response to marcia.marchiori

I suspect you are looking at the installer disk image that is part of the installation system. Have you tried restarting the computer to see if the installer will pick up and continue? If the installer does not continue then get yourself back into the Recovery HD. Click on the Install OS X option in the Utility Menu and click on the Continue button. You may be asked for your Apple ID and/or Admin password so have them handy.

OS X Base System only disk available

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