rsync --append behavior

Paul Slootman paul at
Tue May 22 09:42:29 GMT 2007

On Sat 19 May 2007, Jacob Balazer wrote:

> I am using rsync 2.6.9 in daemon mode under Cygwin, and having trouble
> reconciling its --append behavior with that described in the man page:
> The man page says that when you use --append, it will update a file by
> appending, which presumes the existing data on the receiving side
> matches.  But when I run rsync with append mode when the existing file
> on the receiving side is shorter than on the sending side, the first
> thing it does is (I think) is to read either most of or all of the
> file on the remote sending end: on the local receiving end, it says
> "recv_generator()" for each of the files, "generating and sending sums
> for 1", and then "generate_files phase=1", and then no progress for
> several minutes.  After that several minutes, apparently a
> block-by-block comparison of the existing data starts.  This operation

Rsync will always do a checksum verification of updated files, even with
--append. The manpage also says: "If that [the existing data is
identical] is not true, the file will fail the  checksum  test, and the
resend will do a normal --inplace update to correct the mismatched
data.". Hence the file will still be completely read.

Paul Slootman

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