Il 15/01/20 18:54, Jon Pruente ha scritto:
On Wed, Jan 15, 2020 at 11:38 AM Alessandro Baggi <
alessandro.ba...@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/
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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.
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