rsync - Oct 2009 - DO NOT REPLY [Bug 6788] New: rsync does not abort early but needlessly transfers data if destination is write protected

https://bugzilla.samba.org/show_bug.cgi?id=6788

           Summary: rsync does not abort early but needlessly transfers data
                    if destination is write protected
           Product: rsync
           Version: 3.0.5
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: core
        AssignedTo: wayned at samba.org
        ReportedBy: martin at scharrer-online.de
         QAContact: rsync-qa at samba.org


Hi,

I fell victim to a funny behaviour of rsync. I'm using rsync 3.0.5 under
Ubuntu
Linux 9 to copy/sync data from one local disk to another, e.g. to a USB
harddrive which will be mounted e.g. under '/media/usbdisk'.
However, as long the USB drive is not mounted this mounted directory is root
owned and write protected for normal users (to protect them to accidentally
copy files to the wrong physical drive).

Now, if rsync is used to copy data to this or any other write protected
directory the input data seems to be processed as normal. The --progress (-P)
option shows the copy process as normal - sometimes with a very high speed
(e.g. 80 MB/s), sometimes with the read speed of the source media (ca. 20MB/s).
No error appears until the end, then the following message is printed for every
"transfered" file:
  "rsync: mkstemp "/mnt/tmp/.<file>.eBXcOU" failed:
Permission denied"

Of course no files, neither a temp or the final file, are created at the
destination (because the user does not has write permissions). 
It looks to me that the rsync server accepts incoming data while the (temp)
file the data should be written to could not be opened! The error message which
occurs at the beginning is only passed to the client at the very end! This
behaviour does not make sense and can cause a lot of time being wasted.
The same happens for remote copy operations if the destination directory is
write protected. In this case bandwidth is also wasted.

rsync should skip files and print the appropriate error message immediately
after the server fails to open the (temp) destination file.


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https://bugzilla.samba.org/show_bug.cgi?id=6788


matt at mattmccutchen.net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
            Summary|rsync does not abort early  |Skip file transfer if
                   |but needlessly transfers    |destination file cannot be
                   |data if destination is write|opened for writing
                   |protected                   |




------- Comment #1 from matt at mattmccutchen.net  2010-03-17 03:11 CST -------
This is a known drawback of the current rsync protocol.  Fixing it would
require major changes to the protocol.  Since there is no correctness issue, I
would tend to consider this an enhancement request rather than a bug.

There were multiple Debian bugs about this.  I merged them all here:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=151568


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