rsync occasionally produces error messages that may seem a little
cryptic. The one that seems to cause the most confusion is
"protocol version mismatch -- is your shell clean?".
This message is usually caused by your startup scripts or remote
shell facility producing unwanted garbage on the stream that
rsync is using for its transport. The way to diagnose this
problem is to run your remote shell like this:
ssh remotehost /bin/true > out.dat
then look at out.dat. If everything is working correctly then
out.dat should be a zero length file. If you are getting the
above error from rsync then you will probably find that out.dat
contains some text or data. Look at the contents and try to work
out what is producing it. The most common cause is incorrectly
configured shell startup scripts (such as .cshrc or .profile)
that contain output statements for non-interactive logins.
If you are having trouble debugging filter patterns, then try
specifying the -vv option. At this level of verbosity rsync will
show why each individual file is included or excluded.
