Disk is not convertible to APFS

You will need to boot to Internet Recovery (Option Command R)

not the base system—and try again erase/reformat/initialize the parent drive.

You have mounted your Recovery partition— and you can not format successful the Drive that you are mounted to,

The way forward is Internet Recovery and try again.

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

macOS Base System is the Recovery/Installer Volume.

You don't install onto that. You need to find the drive you erased.

Since it is going to install Mojave, you may want to erase it a Mac OS Extended (Journaled), then let it try to install Mojave.

You need to select the Apple SSD… and choose Mac OS Extended (Journaled).

While Mojave will convert it to APFS, the installer sometimes fails if you use an APFS disk as the install destination.

Also, since you are seeing two volumes, HD and Untitled, it doesn't appear you actually erased the drive. You just erased one of the Volumes. That is probably confusing the Mojave installer and it might work if you just erase to APFS.

Sad_scope Said:

"Disk is not convertible to APFS: [...]I have got MacBook Air 2018 with OS Catalina, but today I tried to install the new beta OS Big Sur. I didn’t make any backup for my system and having installed the Big Sur, just like in 10 minutes, I decided to reinstall Catalina. [...]"

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A. Run First Aid:

What happens when you click First Aid? Does all go through successfully? Do you get any errors?

B. No Backup Made?

I strongly recommend doing you make a backup, for securing your device, and then restoring if the reinstall is unsuccessful. You would start by creating a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with this Mac. Use an External Hard Drive at least 1.5 Times the Hard Drive storage. 

C. If you don’t Back Up. your Mac:

If you end up not making one, and then the Mac crashes, then you’d have to take this as a learning experience, and know to always create a backup.

Sad_scope Said:

"Disk is not convertible to APFS: When I click First Aid i can see 'Operation successful' in APFS and in Extended Journal. I have no errors. Yeah, i will always make back up in the future... But now I can only reinstal macOs, but i don't know how.“

———-

Ask this in the Developer Forums:

Big Sur is still in the phase of development. So, with Big Sur playing a big role in this, post your question in there to get the answer you most likely need.

Go Here: https://developer.apple.com/forums/

So I am booted in internet recovery and the Apple macOS base system shows itself as hfs format my sshd is formatted APFS. When I try to install Catalina, in the installer log it says that the internet recovery portion that I am booted into “macOS base system” cannot be converted to APFS. Wth this is so crazy i cannot figure this out. I can’t get a working OS on my drive because of this ridiculousness. So if the Catalina version through internet can’t be converted to APFS how the heck am I supposed to reinstall a new copy of macOS ?

I am facing the same problem. I own a Macbook Pro (mid 2012) on which I had changed the original hard drive to install an SSD. The first installation of Catalina hadn't caused any problems.

Then I had a "bug" of which I don't know the nature and I found myself facing the folder with a question mark at boot time. Saving all the important data in different cloud solutions, I decided to reinstall Catalina (it could only do me good) and now I'm facing the same problem where the installation is done, it starts correctly but then stops and restarts the computer. When I display the installation logs console, the last error log before rebooting shows "disk26s1 is not convertible to APFS..." even though I've erased the disk and it's in that format.

First of all, thank you for your prompt response! My answers below.

TheLittles wrote:

Flecchi Said:

"I am facing the same problem. I own a Macbook Pro (mid 2012) on which I had changed the original hard drive to install an SSD. The first installation of Catalina hadn't caused any problems."

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Consider the Following:

A. Run First Aid:

What happens when you click First Aid? Does all go through successfully? Do you get any errors?

Answer : Everything seems correct, especially since I'm trying to install Catalina on a new SSD, never used.

B. Restore from a Backup:

If you have a backup, then restore your Mac from the backup, trying Big Sur later on.

Answer : Unfortunately, I don't have a backup, but in this case, I don't mind starting from scratch at all.

C. If you didn't Back Up. your Mac:

If you end up not making one, and then the Mac crashes, then you’d have to take this as a learning experience, and know to always create a backup. You would start by creating a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with this Mac. Use an External Hard Drive at least 1.5 Times the Hard Drive storage. 

Answer : I understood that in the future, it would be better to set up regular backups, but that doesn't solve my problem.

You will find herewith, the pictures of the manipulations, as well as the videos of the logs containing the errors (I was not able to save them on a usb key for lack of right apparently)

The photos will be in no particular order you may find the fact that I start from a blank disk, well formatted in "APFS", the first steps of installation, as well as videos containing the installation logs. I found this error on two different SSDs: the first one I had (on which the first installation went well). After my "bug", I sent back the ssd thinking it was defective and I received a new one on which I found the same errors.

The bootable USB key to install Mac OS Catalina was made on an iMac that I also own.

P.S.: it's not possible to install Big Sur on the 2012 Macbook Pro.

[Link Edited by Moderator]

did you manage to install catalina? i faced this problem too

how are you doing? Did you fix the problem?

What was the reason? I also sent it for repair, there is a need to replace the materin board)

Flecchi Said:

"I am facing the same problem. I own a Macbook Pro (mid 2012) on which I had changed the original hard drive to install an SSD. The first installation of Catalina hadn't caused any problems."

-------

Consider the Following:

A. Run First Aid:

What happens when you click First Aid? Does all go through successfully? Do you get any errors?

B. Restore from a Backup:

If you have a backup, then restore your Mac from the backup, trying Big Sur later on.

C. If you didn't Back Up. your Mac:

If you end up not making one, and then the Mac crashes, then you’d have to take this as a learning experience, and know to always create a backup. You would start by creating a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with this Mac. Use an External Hard Drive at least 1.5 Times the Hard Drive storage.