diskutil ap convert disk0s2
Converting the volume on disk0s2 to an APFS Volume on an APFS Container
Started APFS operation on disk0s2 (Macintosh HD)
Converting HFS Volume to an APFS Container which will export one APFS Volume
The target is the Journaled HFS+ volume "Macintosh HD" backed by the GPT partition disk0s2
The target is a data disk; it is not a macOS system disk
Found APFS EFI driver /usr/standalone/i386/apfs.efi to install into the APFS Container
The target is not encrypted
Unmounting disk0s2
Starting conversion from HFS to APFS
Performing apfs_hfs_convert -x --verbose=0x400 --efi /usr/standalone/i386/apfs.efi /dev/disk0s2
Reporting post-conversion statistics
A problem occurred during conversion from HFS to APFS
APFS Converter exit code is 1
Aborted conversion in commit mode so will restore type
Setting type of disk0s2 to HFS
Changing the physical disk partition type in shared mode
Partition modification attempt count was 1
Not mounting APFS Volume
Exiting conversion operations with error code -69860
Error: -69860: The underlying task reported failure on exit
Underlying error: 1