MacOS – APFS – Is it possible to install 2 macOS versions inside one APFS container

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As you might already now, a single APFS container can have multiple APFS partitions inside. Their advantage is the free space is shared between partitions.

Today I decided to try out macOS Mojave Public Beta and was about to create a second APFS container, but thought "why not use an APFS partition instead?" but I didn't want to risk my main macOS High Sierra partition being erased so I decided to ask it here. Is it possible to have multiple macOS installations inside a single container with multiple APFS partitions?

Best Answer

Yes, it possible to have multiple macOS installations inside a single container with multiple virtual partitions, but some of the partitions will be shared.

Note: I do not think virtual partitions is the correct terminology. I believe the terminology should be APFS volumes sharing the same APFS partition.

I started with High Sierra installed to volume labeled Macintosh HD in a APFS container. I using the Disk Utility application to add a new APFS volume labeled Macintosh HD 2. Next, I downloaded High Sierra from the App Store and installed to the Macintosh HD 2 volume. The result from diskutil list is shown below.

Note: I used a external drive, so disk2 appears below instead of the expected disk1.

/dev/disk2 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +200.0 GB   disk2
                                 Physical Store disk1s6
   1:                APFS Volume Macintosh HD            50.8 GB    disk2s1
   2:                APFS Volume Preboot                 46.1 MB    disk2s2
   3:                APFS Volume My Recovery             1.0 GB     disk2s3
   4:                APFS Volume VM                      8.6 GB     disk2s4
   5:                APFS Volume Machintosh HD 2         18.2 GB    disk2s5

While both High Sierra installations use different root volumes (disk2s1 and disk2s5), the installations share disk2s2, disk2s3 and disk2s4.

Next, I created another APFS volume labeled Mojava 1 and then downloaded Mojava Beta from this Apple website. The result after installing is shown below.

/dev/disk2 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +200.0 GB   disk2
                                 Physical Store disk1s6
   1:                APFS Volume Macintosh HD            50.8 GB    disk2s1
   2:                APFS Volume Preboot                 74.5 MB    disk2s2
   3:                APFS Volume My Recovery             1.5 GB     disk2s3
   4:                APFS Volume VM                      8.6 GB     disk2s4
   5:                APFS Volume Machintosh HD 2         18.1 GB    disk2s5
   6:                APFS Volume Mojava 1                35.8 GB    disk2s6

Mojava installed to disk2s6 and shares share disk2s2, disk2s3 and disk2s4 with the other two High Sierra installations.

So there is now three macOS Recoveries for both High Sierra and Mojava. In my case, both High Sierra macOS Recoveries are Version 1.0 (327) and the Mojava macOS Recovery is Version 1.0 (330).

I can boot to one of the three macOS Recoveries stored on disk2s3 by holding down the ⌘+R key combination at startup. If the default startup disk is a APFS volume containing macOS, then the corresponding macOS recovery will startup. For example, if the startup disk is set to the APFS volume Machintosh HD 2, then holding down the ⌘+R key combination at startup will result in the Mac booting to High Sierra macOS Recovery on APFS Volume My Recovery.

Note: macOS Recovery no longer appears in the Mac Startup Manager. However, macOS Recovery, for a given macOS installation, can be booted using the rEFInd Boot Manager.

BTW: Removing Mojave from the APFS container is covering in my answer to the question: Erase an APFS volume?

Related Solutions

Partition problem with APFS containers in macOS High Sierra

Well for anyone interested in a solution, it's now possible.

I've followed this guide and managed to reclaim all available space and resize my main partition back to full disk space.

Thanks everyone for help and suggestions.

MacOS – Missing HDD space after running diskutil commands

The folks at Apple seem to be operating under a paradigm where no drive space is ever unallocated. Therefore, when System Integrity Protection (SIP) is enabled, the macOS operating system prevents execution of any utilities or commands which could report the location of lost space on system drives. Your Mac uses a single physical system drive named /dev/disk0.

System drives generally contains two types of partition tables. The first is the Master Boot Record (MBR) table and the second is the GUID Partition Table (GPT). The command fdisk dumps the contents of the MBR table, while the command gpt partially dumps the contents of the GPT. To used these command on a system drive, you need to either disable SIP or execute the commands while booted to macOS Recovery. The commands you need to enter are given below

fdisk  /dev/disk0
gpt  -r  show  /dev/disk0

The gpt commands prints a table of the space occupied by each partition. The table also prints unallocated space. Generally, you need to know which partitions are located before the lost (unallocated) space you wish to recover. Usually, the diskutil command can then used to recovery this space. Although, other commands such as fdisk, gpt and gdisk can also be used.

Note: Generally the identifier produced by disktuil output contains the index for a given partition. This is not alway true. You may need to consider other output from both the diskutil and gpt commands before matching a partition index with an identifier.

If you could post the output from the above commands, then someone (or I) could help with the correct commands to repair your Mac.

Update 1

You can erase the Apple_KernelCoreDump` partition by executing the command given below. The result will a block of free space the the end of your drive. The size of this block will be about 61 GB.

sudo  diskutil  erasevolume  free  n  disk0s5

Beyond this change, I am not sure what to post. I need to know how you want the drive partitioned. So far, you have mentioned partitions for ExFat and Windows. Currently you have Apple_HFS and Apple_Boot partitions. You can not merge the free space back to the APFS container until these partitions are erased. Also, if you are going to reinstall Windows, you probably should state the model/year of your Mac and the version of Windows.

Update 2

The following command will return all free space back to the APFS partition.

sudo  diskutil  erasevolume  free  n  disk0s3
sudo  diskutil  apfs  resizecontainer  disk0s2  0

If the above commands work, are you then going to attempt to install Windows 10 through the use of the Boot Camp Assistant? Other users have reported problems using the Boot Camp Assistant when the internal physical drive has an APFS partition.