I'm trying to learn how to securely wipe free space on the HDD of a MacBookPro 9.1, Quad-Core Intel Core i7 @ 2.60GHz, 16.0GB RAM that is running Mac OS X 10.15.7.
Here is what I've learned and tried so far.
CCleaner (Free v1.18.30) does not respond when I run the "Erase Free Space" tool, after enabling Full Disk Access in System Prefs, then selecting the volume (the only option that shows, "Macintosh HD"), submit my admin password, and clicking "Erase Free Space".
But, because the volume hierarchy shown in Disk Utility is
APPLE HDD HTS727575A9E36 (SATA Internal Physical Disk • GUID Partition Map)
-> Container disk1 (APFS Container)
-> Macintosh HD (APFS Volume • APFS (Encrypted))
-> Macintosh HD - Data (APFS Volume • APFS (Encrypted))
I am left to wonder: to wipe free space in Catalina OS 10.15.7, does CCleaner need to be "pointed" directly at the volume titled "Macintosh HD - Data"?
Of related note: the "Macintosh HD - Data" volume appears to be mounted at /System/Volumes/Data
So, I also tried using the macOS Terminal app.
But sending Terminal command "diskutil secureErase freespace 4 /System/Volumes/Data"
returns "Error with secure disk erase: Secure erase by writing a run of bytes to an APFS Volume makes no sense due to its possibly-unbounded size (-69489)".
1. How can CCleaner "Erase Free Space" be pointed directly to the volume titled "Macintosh HD - Data" that mounts at /System/Volumes/Data?
2. Is there a Terminal-command work-around to the error that returns when sending "diskutil secureErase freespace 4 /System/Volumes/Data"?
Thanks.
