This answer is a continuation of my answer to the question: APFS - Is it possible to install 2 macOS versions inside one APFS container?
You can use Disk Utility under High Sierra to remove the APFS volume containing Mojava. However, removing Mojave also requires steps where commands are issued in a Terminal application window. Below are the steps I used to remove the Mojava.
- Open the Disk Utility application.
- Get the file system UUID of the
Mojave 1 volume . Right click the icon labeled Mojava 1 in the Disk Utility application and select Get Info. In my case, the file system UUID is 0FF6C520-6C07-40ED-9AED-FD6E28A6E406.
- Use Disk Utility to remove the APFS volume containing Mojava. Right click on the icon labeled
Mojava 1 in the Disk Utility application and select Delete APFS Volume....
- Boot to macOS Recovery.
- Open a Terminal application window.
Enter the command below to disable System Integrity Protect (SIP) on next restart.
sudo csrutil disable
Boot back to High Sierra.
Open a Terminal application Window.
Enter the commands below to remove Mojava from APFS Volume Preboot.
diskutil mount disk2s2
cd /Volumes/Preboot
rm -Rf 0FF6C520-6C07-40ED-9AED-FD6E28A6E406
cd ~
diskutil unmount disk2s2
Enter the commands below to remove Mojava from APFS Volume My Recovery.
diskutil mount disk2s3
cd "/Volumes/My Recovery"
rm -Rf 0FF6C520-6C07-40ED-9AED-FD6E28A6E406
cd ~
diskutil unmount disk2s3
Reset the SIP settings, by entering the command given below.
sudo csrutil clear
Restart the Mac
Solution:
EDIT: Thank you to @DavidAnderson for pointing out that the driver file "hfs_x64.efi" is what causes the Mac to be able to see the bootable container on the mac. Please see his answer for a better explanation.
The solution is very brief and involves installing the "driver_x64" folder included with the refind download in refind-bin_X/refind/drivers_x64.
Simply drag and drop this "drivers_x64" folder into the EFI/EFI/refind directory after mounting the EFI. Your EFI refind folder should look like this:
Below are some useful commands that helped me.
How to check which mac model I have
You can enter the following in terminal to see your model number:
system_profiler SPHardwareDataType | grep "Model Identifier:"
How to check if my Mac has NVMExpress
Newer macs will most likely have the NVMExpress SSD Controller. But if you are curious in learning what kind of connection you are using, you can input the following commands, separately.
If your device is SATA it will return the info regarding your SATA hard drive and the connection.
If your device is NVMExpress then it will return info regarding your NVMExpress Hard drive and the connection. Of course if your device is not NVMexpress then it will return nothing.
system_profiler SPNVMeDataType
system_profiler SPSerialATADataType
Example:
Please note that the version of Refind will affect which Volumes you would be able to boot up from. I tested this on Refind version 10.4 and 11.4.
From my testing I found that with 10.4 you will only be able to see the "Macintosh HD" volume.
Any version after and including 11.1 are designed to see the Preboot Volume that comes installed with the upgrade to Mac Os Mojave. For more info regarding Refind revisions you can go here:
http://www.rodsbooks.com/refind/revisions.html
I do find it strange that within the driver folder there is no explicit mention of an "apfs.efi" driver. I probably plan to bring this up to the developer. But it still seems to fix this issue. See below for what I mean:
I hope this helps! This was breaking my head for over a week until this simple solution occurred to me. Hopefully it helps you as well.
Best Answer
I think you're confusing several topics into one question
In your title, you're positing Big Sur and Catalina being installed on an external versus an internal disk. I don't see what the comparison/contrast would be of external and internal drives and why it would be an issue installing either operating system on either drive. I suspect you mean to ask about Catalina being on an internal drive and Big Sur being on an external drive (or vice versa) and how that would work but your question doesn't even hint at that.
In the body of your question, you ask about the issues surrounding having multiple operating systems within the same APFS container; however, it doesn't support the supposition of the title - internal versus external drives. The questions, however, are valid in their own right.
You also ask if issues that aren't technically bona fide issues are resolved in an OS that's still in developer beta stats.
So as to your questions:
Probably. This is still two operating systems running side by side in a single container (if this is how you choose to configure it). But, remember, this is a developer beta not a public beta meaning there are still very significant changes to come. Unless you're planning on submitting feedback to Apple trying to solve this at this stage is an exercise in futility.
Yes. If the issue exists on an internal disk, why wouldn't it continue to exist on an external one? Again, were looking at this from the initial position of internal versus external disks.
However, there is part of your question that could shed some light on what I assume you're asking:
There's nothing that says you can't have multiple APFS containers on a single computer. You could have two internal disks, or two external disks or an internal and an external both with their own APFS formatted containers, one with Catalina (internal) and the other with Big Sur (external). In fact, if you wanted to test Big Sur, I would highly suggest you format and install Big Sur on an external drive and leave your internal drive alone. Either installation with not interfere with the other's Recovery, System, Preboot, etc. partitions.
Having multiple OSes on the same drive is obviously doable as per the links you provided, but it introduces an extra level of complexity you likely don't want to deal with. I'm all for users trying things out and testing, but not at the sake of risking data - especially if this is your "production" or "work" machine. So, yes, having this in a separate container on a separate disk "solves" this.
Ideally, you test on a computer you don't mind getting "hosed up" because you mis-configured drives, but I realize having multiple Macs is outside the budget for a lot of folks; I still encourage testing and experimentation but on a separate drive. Spending $100USD on a quality external USB drive is a lot cheaper than trying to recover your data because you experimented on your internal drive you use everyday. And, as always, make copious backups.