How Best to Install another Version of MacOS on my iMac?

[jaybar]

Hi

I am currently running Catalina on my iMac. I need to maintain Catalina for working remotely. However, I would like to upgrade to Big Sur for non-work, while maintaining Catalina for work.

I can create another volume on my APFS startup drive. Is it best to add the new volume to the OS portion or to the data portion?

Can I have two versions of Catalina until I upgrade to Big Sur?

if so, how do I locate the Catalina installer?

Instead, would I be better off getting Mohave through internet recovery?

I have a Carbon Copy Cloner bootable drive that has backed up my current system. I also have a Time Machine backup. Would I be better off using these?

I don’t really understand what I need to do and how best to do this.

 

[Fishrrman]

I wouldn't "mix" Catalina and Big Sur on the same drive.

What I do myself to have an "experimental version" of Big Sur to boot and use when I feel like it.

Get an EXTERNAL drive of some sort.
It could be a USB3 SSD, or a USB platter-based hard drive (if you have nothing better).

Install Big Sur onto the EXTERNAL drive.

Now you can "switch boot" when you want by booting and holding down the option key CONTINUOUSLY until the startup manager appears -- then select the drive you want and hit return.

I've seen 128gb 2.5 SATA SSDs selling on amazon for $17.
Or, get a 256gb SSD in the $35-40 range.

Then, put it into a case like this:

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)

tinyurl.com

Now you have Big Sur on a "drive all by itself" and you can use it without interfering with your "work set up" on the internal drive.

 

[jaybar]

@Fishrrman

To install Big Sir, on an external drive, does it have to be bootable? If so how?

 

[Fishrrman]

"To install Big Sir, on an external drive, does it have to be bootable? If so how?"

Use disk utility to initialize/erase the drive to APFS with GUID partition format.

Then, just run the OS installer.

When it gets to the part where it asks you WHERE you want to install, point the way to the external drive.

That's it.

 

[jaybar]

Thanks