For Macs using the APFS file system, you can add a new volume to an existing APFS container by using Disk Utility in MacOS. APFS is something unique in that it distributes disk space on demand, which means that one free disk space is shared (compared to HFS + or FAT where disk space is divided into defined allocations).
You can process APFS volumes as a Mac-specific partition, and you can even install different MacOS versions on unique volumes and share the same available disk space between Mac OS releases.
How to add a new volume to an APFS container in MacOS
Be sure to back up with Time Machine or your chosen backup method before changing any disk.
- Open the Disk Utility application found in / Applications / Utilities /
- Select the disk you want to add the new volume from the sidebar, and then click [+] Plus the "Add Volume" button in the menu bar
- Give the new volume a name, and optionally select a format
- Optionally, click on "Size options "Then set:
- Reserve size – this will ensure a minimum storage space for the new volume
- Quota size – this will ensure a maximum storage capacity for the new volume
Now that you have a new APFS volume, you can do whatever you want with it.
You can set the new APFS volume as a MacOS-specific disk partition, or you can even install another MacOS system software version on the new volume, as long as the MacOS release is compatible with APFS (a newer version like Catalina, Mojave, High Sierra and later).
For an example of using APFS volume in containers, some users create a new APFS volume and use the new volume to run beta software, such as installing MacOS Catalina beta, but be absolutely sure you back up all your Mac data before doing so.
Note that you cannot install Linux, Windows, legacy Mac OS X releases or other operating systems on an APFS volume. However, you can install Windows 10 on a Mac using Boot Camp as described here. Installing Windows, Linux or an older Mac OS X release will create a new partition on the drive either, since it is not possible to install these operating systems on an APFS volume.
Of course, you can also delete an APFS volume from a container in the Disk Utility, just by selecting the volume you want to remove and clicking the minus button and confirming that you want to delete the APFS volume from that container.