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RecentlyConverted

macrumors 6502a
Original poster
Oct 21, 2015
901
644
Hi,

I run my Macs with external drives (rather than the internal), and backup to another external drive.

Since 2014, I have never had a problem updating the OS, even with this update, one iMac updated just fine. The second came up with the message "macOS could not be installed on your computer". It suggests going into diagnostics, but on powering on and holding D, it just tries to install the OS and fails again.

The computer is fine, as I changed the start up disk to internal, and that updated OK. I tried booting from my (CCC) back up drive, but when I tried to put the new OS update on that it failed too.

All very strange. Any ideas?

Thanks
 

usagora

macrumors 601
Nov 17, 2017
4,869
4,456
Hi,

I run my Macs with external drives (rather than the internal), and backup to another external drive.

Since 2014, I have never had a problem updating the OS, even with this update, one iMac updated just fine. The second came up with the message "macOS could not be installed on your computer". It suggests going into diagnostics, but on powering on and holding D, it just tries to install the OS and fails again.

The computer is fine, as I changed the start up disk to internal, and that updated OK. I tried booting from my (CCC) back up drive, but when I tried to put the new OS update on that it failed too.

All very strange. Any ideas?

Thanks

Could you clone your internal drive to an external and see if it boots from that external ok afterwards?
 

RecentlyConverted

macrumors 6502a
Original poster
Oct 21, 2015
901
644
Could you clone your internal drive to an external and see if it boots from that external ok afterwards?
Hi,

I don´t have another drive here, so don´t want to wipe one to try (as I still need to get my data back and this way I get two attempts). Is there anyway I could add a partition to a drive, and back up to there, and then boot from there? I can´t find a way to boot from a specific partition, rather than a drive.

Its ok, I set it up and saw the partition as an option.
 
Last edited:

usagora

macrumors 601
Nov 17, 2017
4,869
4,456
Hi,

I don´t have another drive here, so don´t want to wipe one to try (as I still need to get my data back and this way I get two attempts). Is there anyway I could add a partition to a drive, and back up to there, and then boot from there? I can´t find a way to boot from a specific partition, rather than a drive.

I thought each partition would show up as a separate selection under System Preferences > Startup Disk. Have you actually confirmed yourself that they don't? Not sure if one of these articles would help. If the drive you want to partition is formatted in APFS, then see the 2nd article.


 

RecentlyConverted

macrumors 6502a
Original poster
Oct 21, 2015
901
644
I have booted up from the partition with the backup from the iMac internal HDD, and its running fine with the new version of Catalina. I just need to install it on my main partition.

The OS downloads ok, gets to 27 mins remaining, stays there for ages, then comes up with the error.
 
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