Upgrade to Catalina - missing EFI partition

[daveinacave]

Hi,

A long time ago I updated to El Capitan. After that due to work/studies I haven't updated updated and now trying to update to Catalina. When trying to do this I got the message that my main disk (/disk0) "cannot be used to start my computer".

I usually boot from USB, post installation I skipped booting from the HD as for some reason (I don't remember quite why now - this was 6 years ago). After digging a bit I noticed that my main disk (/disk0) does not have an EFI partition (the Clover folders yes, but the partition was either not created or has been borked/removed somehow). My backup disk (/disk03) does however have the EFI partition (though I do not want to install on that as it is a HDD (rather than SDD). Screenshot below.

How can I recreate my EFI partition? Do I need to clone the partition from my backup disk or the USB?

I searched for a fix for this, but couldn't see anything specific here or on any other forums.

Many many thanks in advance for any advice on how to fix this! Would prefer to not have to do a clean install if possible, but not sure where to go from here.

 

[UtterDisbelief]

Hi,

A long time ago I updated to El Capitan. After that due to work/studies I haven't updated updated and now trying to update to Catalina. When trying to do this I got the message that my main disk (/disk0) "cannot be used to start my computer".

I usually boot from USB, post installation I skipped booting from the HD as for some reason (I don't remember quite why now - this was 6 years ago). After digging a bit I noticed that my main disk (/disk0) does not have an EFI partition (the Clover folders yes, but the partition was either not created or has been borked/removed somehow). My backup disk (/disk03) does however have the EFI partition (though I do not want to install on that as it is a HDD (rather than SDD). Screenshot below.

How can I recreate my EFI partition? Do I need to clone the partition from my backup disk or the USB?

I searched for a fix for this, but couldn't see anything specific here or on any other forums.

Many many thanks in advance for any advice on how to fix this! Would prefer to not have to do a clean install if possible, but not sure where to go from here.


View attachment 489252

Hi there.

Well it looks like Windows is installed on disk0 so although disk util says it is a GUID partition scheme, there's no formatted EFI on there.

Try running EFI Mounter v3.1 and check if it offers you a "disk0s1" to mount. If not it will only offer disk3s1 (perhaps).

You may still be able to format the EFI to ms-dos or fat BUT this will make Windows unbootable.

Let us know more...

 

[daveinacave]

Thanks UtterDisbelief!

I tried running EFI Mounter, but as suspected it only picked up the USB and disk3 (not disk0).

I am not sure how I managed this in the past, but I dual boot windows with Mac OSX. I don't remember doing anything special during the last upgrade.

When I did the original (Maverics) build I had to use a mix of techniques from the following guide to create MBRs and then re-order the MBR table. Not sure if this is connected?

http://www.tonymacx86.com/mavericks...ricks-asus-maximus-vi-formula.html#post816016

http://lifehacker.com/5698205/how-to-triple-boot-your-hackintosh-with-windows-and-linux

http://jonsview.com/fixing-mbr-tables-on-imac-or-mbp-triple-boot-setups

 

[daveinacave]

One other thing I was thinking about doing is installing to my backup HD (disk03) and then using Carbon Copy Cloner to copy across to my main drive (disk0). Any reason that would not work?

Thanks for your help

 

[UtterDisbelief]

One other thing I was thinking about doing is installing to my backup HD (disk03) and then using Carbon Copy Cloner to copy across to my main drive (disk0). Any reason that would not work?

Thanks for your help

Okay.

Before I reply, I note someone has left a hint in your Profile to update the information there. Please do this .

As far as I know CCC doesn't copy the hidden EFI partition. So doing that will not make the drive bootable.

If macOS (or OS X) booted before then it either booted to UEFI which means a valid EFI partition somewhere in your system that it used or you installed as Legacy which puts the EFI folder tree in the root of your main drive.

No other way to start macOS except from a bootable USB memory stick.

 

[daveinacave]

Thanks UtterDisbelief

I am actually OK having a bootable USB (I have plenty of space behind my PC and have backupclover USBs just in case there is a failure). I am not to fussed about booting via the drive as long as I can access it when booting from a USB (this is what I have been doing for years with El Capitan). If I upgrade disk03 to Catalina and then (after checking that everything is OK) use CCC to clone disk3->disk0 will I still be able to boot into disk0 by USB?

That seems like the easiest option for me now if it would work...

 

[daveinacave]

Hi,

I updated my profile (didn't say that in my last post), but still not sure of the approach mentioned above. Do you think doing that will work?

To make it more readable. The approach is:

1 - Install Catalina to disk3
2 - Check instalation on disk3
3 - Use Carbon Copy Cloner to clone disk3 -> disk0
4 - Boot to disk0 from USB (as I am currently doing)

Many thanks in advance for your help with this!!!

 

[daveinacave]

Hi,

Sorry for the delay in getting back. Life got in the way :/

Looking at this in more detail. I do have an EFI folder in the root of my primary drive (disk0). This has two folders, Boot and Clover (please see photos).

Is there any way of promoting this to an EFI partition or mounting it manually? The EFI mounter did not pick it up.

Many thanks,