Reformat of M1 Big Sur

The other solutions didn't work for me, but it's actually really easy to fix, Apple Support (phone) was incredible, call them if this doesn't work for you:

My issue was that I had accidentally hit "Erase" instead of "Erase Volume Group" on Macintosh HD. The "Erase Volume Group" option would have basically erased the container that contains both "Macintosh HD" and "Data" internal volumes, instead of just Macintosh HD.

1) In Disk Utility, go to View and choose ""Show all" (I believe the shortcut is CMD+2)

2) Select the disk that contains Macintosh HD and Data. In my case it was called "disk3". Erase that disk. It might warn you that you will need internet to reinstall/activate your Mac, that's fine.

3) You now need to reinstall macOS now. But in my case, I had an error at some point before that, where the Recovery Assistant opened and said "Your Mac has no volumes to recover". If you get that error, in the menu bar, tap "Recovery Assistant" and then "Erase".

That's it, after that you should be able to restart your Mac (open the start options through CMR+R on Intel or long-press on power button on M1) and reinstall macOS.

I think you must have only erased Macintosh HD but not data, erase both. This solved my problem

The best way would be to select either one and click "Erase Volume Group". Doing that actually deletes the data volume altogether, and erases the system volume "Macintosh HD".

If you erase both volumes, but don't delete the data volume, you'll have an extra empty volume sitting in your container. Thankfully it's easy enough to delete with Disk Utility (but be careful).

I was unable to delete the container disk (got an error message) but I was able to individually delete the two items therein, and then successfully proceed to macOS reinstall.

Yes, this worked! I just had to also delete the data file and restart with the flash drive with Big sur

If you get stuck (as I did), I would highly recommend calling Apple, since these M1's are not even a year old, and the techs are happy to help. Took about an hour for two techs to figure it out, but at least I wasn't guessing anymore. I just had to keep my i phone camera pointed at the M1 screen so they see what's going on. Creepy, but in this case, a God-send.

hi! what do u mean by reset password? and how to do that? what did you type on the terminal? i got the same issue and really confused on what to do:(. could you please explain it in more detail? thank you so much

This is why I love the Internet!

Got stuck yesterday evening (some people would call it night ...) after erasing my hard disk on my macbook Air M1.

I wanted to do a fresh install of Big Sur.

The "trick" with the terminal and resetpassword command did it for me, and after that I could successfully continue with reinstalling Big Sur from my USB-drive.

Looked pretty straightforward up to step 2. But when I was about re install OS, there were no drives showing up. I went into disk utility, and the whole container ("disk3") showed up as Unmounted. Tried first aid "First Aid Process Failed". Tried mounting Macintosh HD 'Could not mount Macintosh HD' (com.apple.DiskManagement.disenter error 49229). Looks like I need to call Apple

Same issue here. Not possible to re-install Big Sur. Apple Recovery Startup do not gives option for Terminal.

this is what helped me. 100%

https://youtu.be/duXxWDUk2UI

If you get a personalization error when reinstalling macOS on your Mac with Apple M1 chip

This is the correct answer.

Thank you @kevindevq - this was super helpful and I fixed the issues while on hold to Apple Support, who ended up not being able to give me an answer anyway! Thank you so so much!!!

https://discussions.apple.com/profile/kevindevq

answer worked. Thank you!