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User profile for user: Tom Wolsky
Tom Wolsky Author
User level: Level 10
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Erasing an external Big Sur system drive

I have Big Sur installed on an external SSD. It's of course the usual two partition drive that looks like this



How can I erase this drive? If I try to erase the Micron, it fails. Same thing if I try to erase the container. I can erase each partition, but then I'm left with a drive with two partitions. Even after erasing the partitions I still can't erase the full drive.


On a internal system drive this is not a problem. You simply boot into recovery mode and erase the drive. AFAIK you can't boot into recovery mode from an external boot drive, or I haven't found a way.


So how do you erase a drive like this, or boot into recovery from a drive like that?


Thanks very much for any guidance.

Posted on Nov 17, 2020 4:32 AM

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User profile for user: putnik
putnik
User level: Level 4
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Posted on Nov 17, 2020 5:11 AM

I think your terminology is wrong, as the Container has two "Volumes", one for the OS system and one for the user account Data. This is different from "Partitions" that give distinct areas on the disk. You can have several Volumes using the same disk space.


I also had trouble getting rid of the volumes. I think you need t use the +/- icons in Disk Utility. To rid myself of the Container, I think reformatting the disk HFS+ unencrypted will do this for you. Then I did a few First Aid checks before reformatting APFS.


I find that Disk Utility does not always update it's display after taking these actions. I once ended up with three volumes showing, but, after closing/reopening Disk Utility, they disappeared and things went back to a normal single volume.


The BS installer will then make it's own changes to the disk as it requires.

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User profile for user: putnik
putnik
User level: Level 4
1,179 points

Nov 17, 2020 5:11 AM in response to Tom Wolsky

I think your terminology is wrong, as the Container has two "Volumes", one for the OS system and one for the user account Data. This is different from "Partitions" that give distinct areas on the disk. You can have several Volumes using the same disk space.


I also had trouble getting rid of the volumes. I think you need t use the +/- icons in Disk Utility. To rid myself of the Container, I think reformatting the disk HFS+ unencrypted will do this for you. Then I did a few First Aid checks before reformatting APFS.


I find that Disk Utility does not always update it's display after taking these actions. I once ended up with three volumes showing, but, after closing/reopening Disk Utility, they disappeared and things went back to a normal single volume.


The BS installer will then make it's own changes to the disk as it requires.

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User profile for user: putnik
putnik
User level: Level 4
1,179 points

Nov 17, 2020 7:38 AM in response to Tom Wolsky

I was trying to do an Erase/Install from a USB Installer, which gives basic facilities like Disk Utility and Internet Recovery options. On my first attempt, the disk had a System Volume and a Data Volume already and the installer made yet another volume, so I had three, two in use.


I individually deleted the volumes with the +/- icons before being able to delete the Container. I don't think you could reformat HFS+ right away, but someone may prove me wrong and it may be an unnecessary step anyway, once you have a single APFS volume, ready for the installer to do it's thing.

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Erasing an external Big Sur system drive

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