apfs space-sharing

// a quick run-thrgouh of creating two space-sharing volumes on one apfs container

// save me a lot of typing
$ alias apfs="diskutil apfs -IHaveBeenWarnedThatAPFSIsPreReleaseAndThatIMayLoseData"

// create an apfs image
$ hdiutil create -fs APFS -size 20GB apfs.sparseimage
WARNING: You are using a pre-release version of the Apple File System called
APFS which is meant for evaluation and development purposes only.  Files
stored on this volume may not be accessible in future releases of OS X.

You should back up all of your data before using APFS and regularly back up
data while using APFS, including before upgrading to future releases of OS X.

Continue? [y/N] y
created: /Users/soneil/Desktop/apfs.sparseimage

// and attach
$ hdiutil attach apfs.sparseimage
/dev/disk3          	GUID_partition_scheme
/dev/disk3s1        	EFI
/dev/disk3s2        	Apple_APFS
/dev/disk3s2s1      	41504653-0000-11AA-AA11-0030654	/Volumes/untitled

// note s2s1; disk3s2 is the container, s2s1 is the volume

// unmount the volume, but leaving the container attached (not ejected)
$ hdiutil unmount /Volumes/untitled
"/Volumes/untitled" unmounted successfully.
$ diskutil list /dev/disk3
/dev/disk3 (disk image):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        +21.5 GB    disk3
   1:                        EFI EFI                     209.7 MB   disk3s1
   2:                 Apple_APFS                         21.3 GB    disk3s2

/dev/disk3s2s1 (external, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                APFS Volume untitled               +20.5 KB    disk3s2s1

// add a new volume to the container
$ apfs addVolume disk3s2 APFS SecondVolume
Exporting new shared unencrypted APFS Volume "SecondVolume" from APFS Container Reference disk3s2
Started APFS operation
Adding APFS Volume to APFS Container
Creating APFS Volume
Created new APFS Volume disk3s2s2
Mounting APFS Volume
Finished APFS operation

// reattach the original volume
$ hdiutil mount /dev/disk3s2s1
/dev/disk3s2s1      	41504653-0000-11AA-AA11-0030654	/Volumes/untitled

// and admire the result
$ apfs list

======================================================================================================
ENUMERATION OF ALL CURRENT APFS OBJECTS

APFS CONTAINER: REFERENCE:     disk3s2     Total Container Size = 21.3 GB (21265080320 Bytes)
|                                          Container Free Space = 21.2 GB (21203574784 Bytes)
|
|--<  APFS PHYSICAL STORE:     disk3s2
|
|-->  APFS VOLUME:             disk3s2s1   Volume Name = untitled (/Volumes/untitled)
|                                          Space-Sharing Current Volume Size = 24.6 KB (24576 Bytes)
|
|-->  APFS VOLUME:             disk3s2s2   Volume Name = SecondVolume (/Volumes/SecondVolume)
|                                          Space-Sharing Current Volume Size = 24.6 KB (24576 Bytes)
|
======================================================================================================

---------------------------------------------------------------------
APFS OBJECTS BY ITERATING ALL CURRENT DISKS WHILE CHECKING APFS ROLES

APFS PHYSICAL STORE = disk3s2   -> APFS CONTAINER REFERENCE = disk3s2
APFS VOLUME =         disk3s2s1 -> APFS CONTAINER REFERENCE = disk3s2
APFS VOLUME =         disk3s2s2 -> APFS CONTAINER REFERENCE = disk3s2
---------------------------------------------------------------------