On Sun, Mar 29, 2026 at 11:37 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wrote:
> > However ... I do not find any indication in the GNU tar docs
> > that it produces sparse files by default. It looks like you
> > need to say -S/--sparse to make that happen. Maybe you have
> > a version that's been hacked to make that the default?
>
> Bleah. Digging in the man pages at freebsd.org, I read
>
> --read-sparse
> (c, r, u modes only) Read sparse file information from disk.
> This is the reverse of --no-read-sparse and the default behav-
> ior.
>
> It's apparently been there and been default since FreeBSD 13.1.
> This leads one to wonder how come BF member dikkop is managing
> to run this test successfully. I speculate that it's using a
> filesystem type that doesn't do sparse files (cc'ing Vondra
> for confirmation on that).
>
> It looks like to make this test stable on modern FreeBSD,
> we need to see if tar accepts --no-read-sparse and use that
> switch if so.
Yeah. Here's my attempt at perl.
I think your Mac probably has a similar tar program BTW... but apfs
probably doesn't go around making holes visible to lseek()
automatically or at least as eagerly as my ZFS system.
