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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!

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

Pic 2 - When I press the + sign nothing happens

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

Best reply

marcia.marchiori Author

Level 1

38 points

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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32 replies

Feb 9, 2018 1:31 PM in response to Csound1

No, partitioning is not available for that one as well, neither is erase, restore or unmount.

Feb 9, 2018 1:33 PM in response to Kappy

All of the options that are not available for the OS X Base System disk are also unavailable for the topmost disk option, as if they are the same thing...

Csound1

Level 9

59,973 points

Feb 9, 2018 1:50 PM in response to marcia.marchiori

Are you explicitly selecting the first entry in the lefthand column?

Csound1

Level 9

59,973 points

Feb 9, 2018 2:08 PM in response to marcia.marchiori

In picture 2 it looks as if the size dialog is active, is it? and I yes can you alter it at all?

And, how did you boot the machine, standard, recovery or internet recovery?

Csound1

Level 9

59,973 points

Feb 9, 2018 2:29 PM in response to marcia.marchiori

I am out of ideas I'm afraid, maybe Kappy will fill us in.

Csound1

Level 9

59,973 points

Feb 9, 2018 2:30 PM in response to Csound1

I would still like to know what you are booted to though.

Feb 9, 2018 2:43 PM in response to Csound1

Sorry, forgot to answer that one: I simply turn the computer on and it goes directly to Internet Recovery (without entering any shortcuts during start up).