Il 15/01/20 18:54, Jon Pruente ha scritto: > On Wed, Jan 15, 2020 at 11:38 AM Alessandro Baggi < > alessandro.baggi at gmail.com> wrote: > >> Hi Jon, >> I wrote in the first mail the script with the current order of command >> that I used. Try to run in a bash script and you will see the result. >> >> If not my sequence is: >> >> dd if=/dev/zero of=src/testfile bs=1M count=100 >> rsync -avS src/ dest/ >> du -h dest/testfile >> du -b dest/testfile >> >> for urandom: >> >> dd if=/dev/urandom of=src/testfile bs=1M count=100 >> rsync -avS src/ dest/ >> du -h dest/testfile >> du -b dest/testfile >> >> without --sparse the same as first sequence without -S option. >> >> But why du reports 0M when with -b reports correct bytes and why this >> happens only with zeroed file? >> >> > Ah, I misunderstood what you meant. I had thought you might have created a > file with urandom first and then overwrote it with zeros. This is behaving > as expected with sparse files. You can create a sparse file with dd by > using seek: > https://www.thegeekdiary.com/how-to-create-sparse-files-in-linux-using-dd-command/ > _______________________________________________ > CentOS mailing list > CentOS at centos.org > https://lists.centos.org/mailman/listinfo/centos Thank you for the suggestion. I meant -S of rsync to use disk space efficiently but this is a (great) misunderstood. Now I read again rsync man page (and your link) and this means "treat sparse files efficiently to save space on disk". My question is: is rsync capable to detect sparse files from "regular" files? If -S is invoked and no sparse files are not in dataset, it treats those files as sparse files or "regular" files? Why I get different behaviour using urandom and /dev/zero? This is casual/accidental? Thank you again for your help.