Apple’s new APFS (Apple File System) format is the default format for storage under macOS 10.14 Mojave, replacing the dependable and long-lived HFS+ format. However, there are still some instances where HFS+ needs to be used. For example, APFS is incompatible with Apple’s Time Machine backup application and FileVault 2 (which is used to encrypt full drives), and cannot be used to format Fusion drives — those drives that use a combination of a solid-state drive and conventional hard disk drive. What if you accidentally format a drive in the APFS format and then realize you can’t use Time Machine or FileVault 2? I recently ran into this dilemma when I formatted an external drive in the APFS format and it was unusable by Time Machine. In this tech tip, I’ll show you how to revert back to HFS+.
You can’t just use Disk Utility to reformat an APFS disk to HFS+ — once it has been converted to APFS, the only options that appear for erasing an APFS disk are to reformat in APFS. The method I’m showing here requires some familiarity with the Terminal application, which can be found in /Applications/Utilities.
Deleting the APFS Partition
Launch the Terminal app, type the following command at the prompt to locate the Physical Store identifier of the APFS partition, and press Return:
I have quite a few disks both in and attached to this iMac, so there’s a long list as seen in the screenshot above. The important thing is to find the drive we wish to revert to HFS+. In this case, it’s the drive listed at the bottom. It is listed as an APFS Volume with a name of ‘OWC Mercury Elite Pro mini‘ and a physical store reference of disk5s2
What I want to do now is destroy the APFS partition. This can be a bit dicey if you have data stored on the drive, in which case you will need to back up the data to another drive. To do this, we’ll type the following command:
diskutil apfs deleteContainer /dev/disk5s2
If you’re following these instructions, you’ll need to replace disk5s2 with the correct identifier for your drive.
By default, the drive is wiped as an APFS disk, then initialized as a case-insensitive HFS+ volume with the name ‘Untitled’. If you wish to change the name back to something more recognizable, such as ‘OWC Mercury Elite Pro mini’, that can be done in one of two ways:
1) In a Finder window, locate the drive ‘Untitled’, right-click on it, and select “Rename ‘Untitled'” (see screenshot below). Type in the new name, then press Return.
2) In Disk Utility, click on the drive ‘Untitled’ to select it in the left sidebar, then click the Erase button at the top of the window. Type in the new name for the drive (in this case, ‘OWC Mercury Elite Pro mini’), make sure that ‘MacOS Extended (Journaled)’ is selected as the format, and click Erase (see screenshot below).
The key thing to remember is that reverting to HFS+ from APFS is a destructive change — any data on the drive that you’re switching back to HFS+ will be fully erased. Be certain to back up any important data on the drive prior to attempting the change.
Read more on APFS at the Rocket Yard:
- OWC VP of Software Engineering Talks APFS, T2 Chip at MacSysAdmin 2018
- Tech 101: Explaining the New Apple File System (APFS)
- First Aid: Verify and Repair HFS+, APFS Drives with Disk Utility
- Translating Apple’s New High Sierra & APFS Compatibility Document
- Partition Drives & Create APFS ‘Containers’ for Space Sharing with Disk Utility
- Using APFS On HDDs … And Why You Might Not Want To
- Can APFS be used with Time Machine, Boot Camp, and File Vault?
- The Speed of APFS: Just How Fast Is It?