[colug-432] creating sparse disk images

[Rick Hornsby]

On November 13, 2018 at 11:13:31, Matthew Hyclak (hyclak at gmail.com) wrote:

Been a while since I did this, but I believe you have to make sure the
filesystem you want to be sparse actually contains 0's in the places you'd
like to be sparse before creating the sparse file.

https://unix.stackexchange.com/questions/44234/clear-unused-space-with-zeros-ext3-ext4
 looks like a good starting point.

Thanks. I had seen that thread. I used zerofree, but it didn’t seem to
matter. Because of your link though, I read farther down the page to some
information about cp with the ‘—sparse=always’ flag, and some hints about
reported size between ls and du.

Interestingly enough, I messed around and got the following:

cp —sparse=always 16GB_file sparse_file -> 3.7GB, as per du. ls still says
it’s 16GB.
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