Discrepancy between df and duf on macOS

[sryze]

When I run duf on a MacBook (macOS 12.6, APFS) it shows different info for some of the system volumes compared to the info printed by df, e.g. "Used" space of /System/Volumes/Preboot and /System/Volumes/VM .

df output:

duf:

[Lan-ce-lot]

I found the same problem on my MacBook(macOS 12.51, APFS) too.

df -h

duf

In the df, Used+Avail ≤ Size
But in the duf, Used+Avail == Size
So the df might be the problem?

[sryze]

As far as I understand, the free space of an APFS container is shared between all volumes of that container and can be allocated to them on demand, therefore used + available space will not be equal to total size for its volumes.

[sryze]

I found that the information about a volume's used space is provided by the getattrlist() system call, but it's not implemented in Go yet. This is what df uses internally for the "Used" column.