[lug] Convertion of ext4 Sparse Files

[Aaron D. Johnson]

In message <1314319731.13063969.1515196473107.JavaMail.zimbra at comcast.net>, stimits at comcast.net writes:
> Where is the "--sparse=3Dnever" from? My Fedoras all use just
> "--sparse=never", no "3D"...the same goes for an Ubuntu 16.04 system
> I have. I've never seen th e "3Dnever" version.

Hmmm.  "=3D" is quoted-printable encoding for "=".  So some kind of
MIME encoding weirdness there.  You do not need the "3D" part.

> FYI, I can see the allocated block size ("ls -ls") versus written
> size ("ls -l") and verify my partition image has sparse ignored and
> no matter what I do cp and dd always copy this verbatim without any
> expansion. If I start with a file created from truncate I do get the
> same results, but the tools seem to underst and an empty file.

What filesystem are you doing this on?  ZFS, btrfs, XFS may all do
"smart" things that you're not expecting here.  Boring old ext[23]
will behave as I've outlined in earlier message.  My earlier output
was done on ext4 and it looks like I'm expecting as well.

Additionally, I don't think I understand why your file being sparsely
allocated is an issue.  (I may have missed it -- lots of email today.)
Can you outline that for your readers?  (Or point to earlier
explanation.)

- Aaron