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Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
I recently installed Big Sur on my MacBook Pro. I hated it so I tried to go back to Catalina. When I erased the partition somehow I deleted it and now I am left with Mac OS base system and above it there is the uninitialized APPLESSD APO256M Media. I can’t seem to create a new partition for Macintosh HD to install the OS and I’m freaking out!!! Can someone please help me?!?
 

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Rodan52

macrumors 6502
So you have the Base System which is essentially the Recovery Partition. Have you tried booting into the recovery partition?
Shut down and restart holding down the Command and R keys until you see a window on a plain grey background.
On that window you should see Restore options and Disk Utility.
You should see an option to reinstall macOS, choose this option and sit back and wait.
 

Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
I power off and then power on holding option+r. It brings me to a spinning globe asking me to sign into wifi. I’ve signed in and am waiting......

thanks for responding guys, I really appreciate the help. As soon as something happens I will follow up.
 

Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
Well I am back in disk utility and still no option to to partition or re-create Macintosh HD. Omg! This is bad!!
 

Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
So you have the Base System which is essentially the Recovery Partition. Have you tried booting into the recovery partition?
Shut down and restart holding down the Command and R keys until you see a window on a plain grey background.
On that window you should see Restore options and Disk Utility.
You should see an option to reinstall macOS, choose this option and sit back and wait.
I tried to reinstall Mac OS but when it asked me where I want to install there was no option!!
 

Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
So you have the Base System which is essentially the Recovery Partition. Have you tried booting into the recovery partition?
Shut down and restart holding down the Command and R keys until you see a window on a plain grey background.
On that window you should see Restore options and Disk Utility.
You should see an option to reinstall macOS, choose this option and sit back and wait.
 

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Rodan52

macrumors 6502
Not unless you already have one. Time Machine is a native Mac backup app which creates a backup of your entire laptop onto an external hard drive.
Apart from allowing you to restore individual files it can also boot your laptop into its own Recovery Partition (a copy of the one on your internal HD).
That means you have a way of erasing and reformatting your hardrive. It can't reformat itself.
You need to erase the internal HD at the level of the Apple SSD Media (which includes the Base System) rename it Macintosh HD, reformat it and remap it. Simple to do if you have an external bootable source. Then you can reinstall Mojave.
I'm not sure what your level of expertise is, I don't mean to talk down to you but if this all sounds too complicated you might be best advised to take it for repair.
What I would normally advise would be to obtain a bootable installer for Mojave. You can create one easily enough but you need a working Mac to do it.
 

Jamiejah

macrumors newbie
Original poster
Nov 26, 2020
7
0
I should be ok then. This is all taking place on my MacBook Pro. I have a functional MacBook Air. I will try to create a bootable drive with that and see what happens! Thanks for your help. I’ll probably be making my way to the Apple store later this afternoon. Smh
 

mikethebigo

macrumors 68020
May 25, 2009
2,199
874
So, all you need to do is go into disk utility inside of recovery, show all volumes, select the actual SSD itself (APPLE SSD AP0...", and click the erase button. Tell it to create a new GUID partition (which should be the default), change the name from "Untitled" or whatever it is to "Macintosh HD". The disk utility will take care of it. Then, install the OS again.
 
Last edited:
Nov 12, 2020
28
25
No. I have a 2017 MacBook Air. Maybe I could use that?
If what mikethebigo said above fails I suppose you could also use your other Mac to create a bootable USB installer, boot from that, nuke your HD and reinstall the OS from the USB. There are some guides on the internet on how to create an installer. You might have to copy and paste some lines into terminal, but nothing more complicated than that.

Edit: Never mind, already mentioned.
 

Rodan52

macrumors 6502
So, all you need to do is go into disk utility inside of recovery, show all volumes, select the actual SSD itself (APPLE SSD AP0...", and click the erase button. Tell it to create a new GUID partition (which should be the default), change the name from "Untitled" or whatever it is to "Macintosh HD". The disk utility will take care of it. Then, install the OS again.
I think you will find you cannot erase the internal SSD using the Recovery Partition on the the internal SSD. The Base System is unable to erase itself.
 

Quackers

macrumors 68000
Sep 18, 2013
1,937
705
Manchester, UK
Do you still have either a Big Sur USB installer or a Catalina USB installer?
Boot from either and then choose Disk Utility and go from there.
 

mikethebigo

macrumors 68020
May 25, 2009
2,199
874
I think you will find you cannot erase the internal SSD using the Recovery Partition on the the internal SSD. The Base System is unable to erase itself.
It will let you, but what happens is then if you reboot again, you go to a question mark and have to boot with internet recovery. When you are in recovery itself the system is completely loaded into RAM, so you can wipe the SSD entirely to empty and it won't stop you.

To be clear, this is different on M1 Macs and not possible anymore. But on Intel Macs, I did this a ton of times.
 

Rodan52

macrumors 6502
It will let you, but what happens is then if you reboot again, you go to a question mark and have to boot with internet recovery. When you are in recovery itself the system is completely loaded into RAM, so you can wipe the SSD entirely to empty and it won't stop you.

To be clear, this is different on M1 Macs and not possible anymore. But on Intel Macs, I did this a ton of times.
This was my first suggestion but because he erased the Macintosh HD partition Internet recovery could not see where to instal the Mojave OS. See post #7
He needs to erase, Name the SSD as Macintosh HD and reformat and map first.
My best suggestion was to create a bootable installer on his other laptop, a MacBook Air, then use DU on that to the above.
 

Fishrrman

macrumors Penryn
Feb 20, 2009
24,982
10,114
OP:

Try this:

Boot to a special version of internet recovery:
shift option command R
(this will install version of OS the MB originally shipped with)

You'll need your wifi password.
The utilities take a while to load, BE PATIENT.

When you get to the internet utilities, open disk utility.
IMPORTANT STEP: go to the View menu and choose "show all devices".

Now, on the left, click on "the top line" that represents the internal drive.
Click "erase".
Choose APFS, GUID partition format.

When the erase is done, quit disk utility.
Open the OS installer and try again.
 
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mikethebigo

macrumors 68020
May 25, 2009
2,199
874
This was my first suggestion but because he erased the Macintosh HD partition Internet recovery could not see where to instal the Mojave OS. See post #7
He needs to erase, Name the SSD as Macintosh HD and reformat and map first.
My best suggestion was to create a bootable installer on his other laptop, a MacBook Air, then use DU on that to the above.
The point is, if you do the erase command on the drive itself, then disk utility recreates the Macintosh HD partition and you're good to go.
 
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RandomCitizen

macrumors member
Jan 24, 2014
43
0
Goldsboro, NC
Just letting ya'll know, you guys saved my life today. An old 2014 i7 MBP and I accidentally did the dirty and deleted that partition like an idiot. Anyway, thanks especially to Fishermman.
 
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