Dual boot Big Sur and Catalina

[JH1969]

I am going to put a new NVME M.2 drive in my PC to install Big Sur. I already have Catalina working, but I am going to remove this drive as a safe backup option.

First question .... is this a good strategy, is there anything I need to be aware of?

I have built the USB install drive with Opencore and Big Sur and will install as if a new build.

Once this is successful and I am up-and-running, I wonder if I can put the old Catalina NVME SSD in the second M.2 slot on my mother board and then choose which system to boot from????

Will this work?
Any issues I should be aware of? They will have different Opencore versions.... will this matter? Will there be any issues with data stored in NVRAM?

Any thoughts would be really useful, thanks

 

[Leesureone]

I am going to put a new NVME M.2 drive in my PC to install Big Sur. I already have Catalina working, but I am going to remove this drive as a safe backup option.

First question .... is this a good strategy, is there anything I need to be aware of?

I have built the USB install drive with Opencore and Big Sur and will install as if a new build.

Once this is successful and I am up-and-running, I wonder if I can put the old Catalina NVME SSD in the second M.2 slot on my mother board and then choose which system to boot from????

Will this work?
Any issues I should be aware of? They will have different Opencore versions.... will this matter? Will there be any issues with data stored in NVRAM?

Any thoughts would be really useful, thanks

Yes, that will work. I've done it a few times so I can test future releases of OSXI or OpenCore on the secondary drive. I typically end up with the same version of OpenCore on both (serial numbers included) being its easy to copy a working EFI folder from drive to drive and stay current.

 

[JH1969]

Yes, that will work. I've done it a few times so I can test future releases of OSXI or OpenCore on the secondary drive. I typically end up with the same version of OpenCore on both (serial numbers included) being its easy to copy a working EFI folder from drive to drive and stay current.

Leesureone - does that mean that once I am happy the Big Sur drive is working OK, I could copy the EFI from that drive onto (and overwriting the existing EFI) the old Catalina drive, and update it to the latest version of OpenCore?

 

[Leesureone]

Leesureone - does that mean that once I am happy the Big Sur drive is working OK, I could copy the EFI from that drive onto (and overwriting the existing EFI) the old Catalina drive, and update it to the latest version of OpenCore?

Yes, that's exactly what I was saying. You can rename the folder to EFIcat or something else and leave it there. If you are using OpenCanopy and the supporting audio files you will start to run out of room though. If that happens delete whatever folder you don't want anymore and then empty the trash.

Also you don't actually have to physically remove your existing drive but it is safer, more fool proof.

 

[JH1969]

Yes, that's exactly what I was saying. You can rename the folder to EFIcat or something else and leave it there. If you are using OpenCanopy and the supporting audio files you will start to run out of room though. If that happens delete whatever folder you don't want anymore and then empty the trash.

Also you don't actually have to physically remove your existing drive but it is safer, more fool proof.

"Also you don't actually have to physically remove your existing drive but it is safer, more fool proof."

My thoughts precisely - I don't want to get it wrong and install Big Sur over my working installation! Once I'm up and running I'll put the old SSD back in

 

[bmoag]

I think it would be easier and faster to clone your existing Catalina drive, either internally or via usb adapter, and create your Open Core EFI for use directly in the EFI partition of the clone. If the OpenCore EFI works it will not only boot the clone but should then be able to update the clone to Big Sur. Worked for me, in fact has been my strategy for new installs with Clover going back several versions of MacOS. I 've used a MacBookPro to install versions of MacOS on a USB adapted drive, then used that with both Clover and OpenCore.

Its a lot easier to verify your Open Core EFI with an already created clone rather than go through the installation process. You should not harm your existing Catalina by seeing if your OC EFI can boot it from a USB key but I understand your reluctance to try that (if you have a bootable clone of Catalina, which I consider good Hack hygiene, there is no risk).

I've cloned that first Big Sur for use on other platforms, including Ryzen. You need to create unique identifiers for each machine but otherwise they should work like first time installations, updating themselves and everything.

I no longer worry about removing existing OS drives and all my machines dual boot with Windows 10. If you are new to OpenCore you will see that booting to Windows from within OC is not as clean as booting into Windows from Clover. Opinions differ as to the impact on Win 10; I prefer to choose the boot drive with the F key when I start the computer.

 

[JH1969]

I think it would be easier and faster to clone your existing Catalina drive, either internally or via usb adapter, and create your Open Core EFI for use directly in the EFI partition of the clone. If the OpenCore EFI works it will not only boot the clone but should then be able to update the clone to Big Sur. Worked for me, in fact has been my strategy for new installs with Clover going back several versions of MacOS. I 've used a MacBookPro to install versions of MacOS on a USB adapted drive, then used that with both Clover and OpenCore.

Its a lot easier to verify your Open Core EFI with an already created clone rather than go through the installation process. You should not harm your existing Catalina by seeing if your OC EFI can boot it from a USB key but I understand your reluctance to try that (if you have a bootable clone of Catalina, which I consider good Hack hygiene, there is no risk).

I've cloned that first Big Sur for use on other platforms, including Ryzen. You need to create unique identifiers for each machine but otherwise they should work like first time installations, updating themselves and everything.

I no longer worry about removing existing OS drives and all my machines dual boot with Windows 10. If you are new to OpenCore you will see that booting to Windows from within OC is not as clean as booting into Windows from Clover. Opinions differ as to the impact on Win 10; I prefer to choose the boot drive with the F key when I start the computer.

Thanks bmoag - I did try this a few weeks ago and it went awfully wrong!! Took me two days to get the machine to boot successfully .... kept going into BIOS. I think it was a NVRAM problem, I restored from a back up, reset the NVRAM and everything was back to normal ...... but definitely squeaky-bum time, as they say!