Can I run Big Sur and Catalina dual boot?

[Dannydematio]

I’m running a 2020 iMac/Catalina. I have blocked upgrade to Big Sur because a mission critical printer I use a lot, the current drivers only work under Catalina.

So can I attach an external, download Big Sur and switch between OS’s? Might be waiting a heck of long time for new drivers or maybe never get them. If I upgrade to B-S, can I do the opposite and download Catalina to an external and still boot from that when I want to print?

I have a maxed out iMac 27 2020 and Epson R3000 printer.

Any guidance much appreciated.

 

[Fishrrman]

You can do this, but I recommend that you use a SEPARATE DRIVE for Big Sur.
Don't try to run it from a partition on the internal drive.

A small, cheap, modest-capacity (as in 250gb or 500gb) external USB3 SSD would be a good choice for this.

 

[zeratul75]

why not on the same internal, fast ssd?
I have this setup and everything is working super fine.....

 

[Nguyen Duc Hieu]

I’m running a 2020 iMac/Catalina. I have blocked upgrade to Big Sur because a mission critical printer I use a lot, the current drivers only work under Catalina.

So can I attach an external, download Big Sur and switch between OS’s? Might be waiting a heck of long time for new drivers or maybe never get them. If I upgrade to B-S, can I do the opposite and download Catalina to an external and still boot from that when I want to print?

I have a maxed out iMac 27 2020 and Epson R3000 printer.

Any guidance much appreciated.

I would do like this:
1. Clone the internal disk to an external SSD
2. Repartition the internal disk and create a new volume for Big Sur
3. Install Big Sur to this new volume.

If things go wrong, you still have the external back-up of Catalina for the critical print jobs. You can run the iMac directly from the external disk, or clone it back to the internal disk like the current status.

 

[HDFan]

1. Clone the internal disk to an external SSD

This certainly works. But there are gotchas:

1. Your user directory/data will be rooted on the new disk. Data which is updated on the rooted disk won't be updated on the other disk.

2. Some applications will see this as a different install and may give you license issues.

3. Backup programs may cause problems. When I booted to a different disk my Cloud backup was frozen as the backup program knew that it was a different disk. Booting back to my regular disk I had to reactivate the backup, which took some time. The solution was to stop all backup services before doing the clone.

If the backup is not running, then things could get confusing as the disk images differentiate.

I expect that there are other cloud services which might have the same problem.

 

[HDFan]

Thinking about the data issue, if you use iCloud then data which is maintained there (Desktop, Documents) would be updated so you you should be able to see it rooted from either disk. Other data, such as that in ~/Library/Application support would not.

 

[Dannydematio]

I would do like this:
1. Clone the internal disk to an external SSD
2. Repartition the internal disk and create a new volume for Big Sur
3. Install Big Sur to this new volume.

If things go wrong, you still have the external back-up of Catalina for the critical print jobs. You can run the iMac directly from the external disk, or clone it back to the internal disk like the current status.

Thanks, that seems like a smart option. I still haven’t moved on this yet. Still running Catalina. The printer manufacturer appears to have upgraded the drivers but I am double checking before I move to Big Sur. if I am not satisfied I’ll be following your advice. I can’t BU my iPhone again until I move to BigSur, so will move ASAP.

 

[gilby101]

Any guidance much appreciated.

Dual boot and so on will work fine (if done cleanly). But I would not take that path just for print jobs - all the rebooting would drive me nuts.

I would upgrade to BS, install VMware Fusion and run Catalina in a virtual machine just for those pint jobs. I have done similar for my scanner which only works well up to High Sierra.

 

[MisterAndrew]

Don't partition the drive. All you need to do is make another APFS volume with Disk Utility. It will dynamically share free space with the other volume.

 

[gilby101]

Don't partition the drive. All you need to do is make another APFS volume with Disk Utility. It will dynamically share free space with the other volume.

Don't do that!! It is asking for trouble to have two boot volumes in the same container - very likely to end up with one or other (or both) unusable. I wouldn't even partition (though that would probably work) - I would use a different drive.

Just like:

You can do this, but I recommend that you use a SEPARATE DRIVE for Big Sur.

Even then there is potential for issues - for example each boot drive will want to modify the spotlight index on the other one.

For just a printer without BS support, a virtual machine is so much easier.

 

[crystalidea]

Actually we've got Catalina + Big Sur + Boot Camp partitions on a single internal drive (iMac Pro)
Booting into each one works fine.

 

[Dannydematio]

For anybody who might want to know, Epson's current R3000 driver works perfectly fine with Big Sur.
Probably that means most, if not all Epson 3x series large format inkjet will also work, but you need to double check.