Beta 6 won't install

[perquesta]

I am unable to install Beta 6. Instead I get the message: "An error occurred preparing the update. - Failed to personalise the software update. Please try again."

Unfortunately, no matter how many times I try I get the same message.

I'd be grateful for any advice on this please.

 

[cmaier]

I am unable to install Beta 6. Instead I get the message: "An error occurred preparing the update. - Failed to personalise the software update. Please try again."

Unfortunately, no matter how many times I try I get the same message.

I'd be grateful for any advice on this please.

From a web search, someone said:

I managed to fix this and the 'Cannot install error'

Using a combination of the following (I don't know which worked)

1. Reset PRAM
2. Disable Filevault
3. Boot into Recovery and enable Startup Security
4. Use sudo sh -c "softwareupdate -ia" via terminal

Macbook 2015, Previously unable to restart with kernal panics and unable to install/download Public Beta 5

 

[sevoneone]

Had the same issue with Beta 5. Skipped it as 4 was pretty stable. Did the same thing while trying to download Beta 6. I tried all the suggestions above to no avail.

I ended up backing up, making a new USB and doing a clean install of Beta 6. We'll see what happens when Beta 7 rolls out.

 

[perquesta]

Thanks cmaier and sevenone.
I reset PRAM and ensured that Filevault was not active. My computer is a 2017 27" iMac and does not have a T2 chip so Startup Security can't be enabled Softwareupdate produced a lengthy error message.

Sevenone, how did you get the Beta 6 installer? I would be very pleased to try a USB install if I could.

 

[matram]

Big Sur prepares the update by creating new temporary volumes on you disk. Ther has been previous reports of failed updates leading to these volumes remaining and messing with future updates.

Have you used the disk tool and checked if you have such volumes left over on your disk. i belive there was a system snapshot, a volume for firmware, one for the OS itself and a virtual machine to do the upgrade process. i am sorry I forgot the exact names.

 

[perquesta]

Thanks matram. I ran Disk Utility in Recovery and First Aid on my Corestorag Fusion disk. It showed such volumes, but they were hidden and I was not able to delete them.

 

[matram]

If you boot into recovery mode, disk utility is also available there. It may allow you to do more with volumes as Big Sur has not yet booted at that point. Maybe the problem is that the OS has mounted these volumes?

There is also a command line version of disk utility (for the brave 😀) that gives you access to more commands and status information. Sorry for not being able to provide more specific advice.

 

[perquesta]

Thanks to all for your suggestions. But unfortunately it still won't install with the same error message I reported at first.

I wonder if it has something to do with my Corestorage Fusion drive reporting as "EFI Boot" when I start the iMac up.

 

[memo90061]

I'm having the same issue.

 

[perquesta]

I don't know if it is connected, but when I boot into Recovery I can use Disk Utility to access all drives. However, when I try Startup Disk, my internal Core Storage Fusion drive doesn't list. Also, when I try to use Reinstall MacOS, my main drive doesn't show.

 

[matram]

If a disk does not show up in Startup disk it is because it is not a bootable disk.

 

[perquesta]

Yes, it boots, but is described as one of two EFI Boot disks when I press "option" while booting.

 

[matram]

This is a picture of the normal disk structure when you have ONE OS installed. If you have multiple OS installed on different different partitions (e.g. Bootcamp) I guess you would have multiple EFI's.

The structure below should be revealed if you run "diskutil list" in terminal. Hopefully it should tell you which EFI is related to which OS based on the structuring of the disks.

 

[perquesta]

Thanks matram for your very helpful post. I have Big Sur beta 4 installed on both an internal and external drive and both show as EFI.

Can I do anything in diskutil to help the situation, eg deleting the EFI disks (d1sk0s1, disk1s1 and disk3s1) or deleting the Preboot, Recovery and VM disks (disk2s2, disk2s3 and disk2s4)?

The alternative I am considering is to do a very good backup, erase my internal disk, install beta 6 on it and recovery my user files from the backup (Carbon Copy Cloner).

I have been able to get the complete beta6 installer using gibMacOS.

 

[matram]

The boot process starts with firmware in the Mac looking for a special entry in the disk partition table that points to EFI. EFI then proceeds to load either "recovery" or "preboot" followed by booting MacOS on "MacintoshHD". Removing EFI or any other part of the chain will leave you with a system on that disk that no longer can be booted or recovered.

If the problem is caused by the second external disk with BigSur can you not just unmount that? That should leave you with only the internal disk which you could upgrade.

What ever you do, I would recommend a good backup (I always keep three - two TM disks and one CCC)

The simplest solution may then be to wipe the disk.