Only New Files
(From here)
The issue might be caused by different user/group IDs on source and target servers. My case was similar, having all files transferred instead of only the modified/new ones. The solution was to use parameters -t (instead of -a), and -P (equivalent to --partial --progress):
rsync -h -v -r -P -t <source> <target>
```h
or shorter (thanks @Manngo);rsync -hvrPt
This transfers only new files, and files already existing but modified. Parameter -a does too much, like user and group ID sync, which in my case can not work as I have different users and groups on my source and target systems. Therefore with `-a` all my source and target files were always regarded as "different".
The parameters in detail:
<div class='csvtable'><table class='csv vert hpad'>
<thead>
<tr><th>Switch</th><th>Description</th></tr>
</thead>
<tbody>
<tr><td><code>-h</code></td><td>human readable numbers</td></tr>
<tr><td><code>-v</code></td><td>verbose</td></tr>
<tr><td><code>-r</code></td><td>recurse into directories</td></tr>
<tr><td><code>-P</code></td><td><code>--partial</code> (keep partially transferred files) + <code>--progress</code> (show progress during transfer)</td></tr>
<tr><td><code>-t</code></td><td>preserve modification times</td></tr>
</tbody>
</table></div>
# Resources
* [stackexchange](https://unix.stackexchange.com/questions/67539/how-to-rsync-only-new-files)