rsync

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=


Frequently Asked Questions

HP compile
Read-only file system
copies every file
is your shell clean
out of memory
    rsync and cron
    rsync: Command not found
    spaces in filenames
    stderr & stdout
    subscribe

HP compile


For HPUX apparently you need to add the option -Ae to the CFLAGS. Edit
the Makefile and change CFLAGS to:

 CFLAGS=-Ae -O

Read-only file system


if you get "Read-only file system" as an error when sending to a rsync
server then you probably forgot to set "read only = no" for that
module.

copies every file


Some people occasionally report that rsync copies every file when they 
expect it to copy only a small subset. In most cases the explanation
is that rsync is not in fact copying every file it is just trying
to update file permissions or ownership and this is failing for some
reason. rsync lists files with the -v option if it makes any change
to the file, including minor changes such as group changes.

If you think that rsync is erroneously copying every file then look
at the stats produced with -v and see if rsync is really sending all
the data. 



is your shell clean


The "is your shell clean" message and the "protocol mismatch"
message are usually caused by having some sort of program
in your .cshrc, .profile, .bashrc or equivalent file that
writes a message every time you connect. Data written
in this way corrupts the rsync data stream. rsync detects this
at startup and produces those error messages.

A good way to test this is something like:

	rsh remotemachine /bin/true > test.dat

you should get a file called test.dat created of 0 length. If
test.dat is not of zero length then your shell is not clean.
Look at the contents of test.dat to see what was sent. Look
at all the startup files on remotemachine to try and find the
problem.



out of memory


The usual reason for "out of memory" when running rsync is that you
are transferring a _very_ large number of files.  The size of the
files doesn't matter, only the total number of files.

As a rule of thumb you should expect rsync to consume about 100 bytes per
file in the file list. This happens because rsync builds a internal
file list structure containing all the vital details of each file. 
rsync needs to hold structure in memory because it is being constantly
traversed.

I do have a plan for how to rewrite rsync so that it consumes a fixed
(small) amount of memory no matter how many files are transferred, but
I haven't yet found a spare week of coding time to implement it!



rsync and cron


On some systems (notably SunOS4) cron supplies what looks like a
socket to rsync, so rsync thinks that stdin is a socket. This means
that if you start rsync with the --daemon switch from a cron job you
end up rsync thiking it has been started from inetd. The fix is simple
- just redirect stdin from /dev/null in your cron job.


rsync: Command not found


> rsync: Command not found

This error is produced when the remote shell is unable to locate the rsync
binary in your path. There are 3 possible solutions:

1) install rsync in a "standard" location that is in your remote path. 

2) modify your .cshrc, .bashrc etc on the remote machine to include the path
that rsync is in

3) use the --rsync-path option to explicitly specify the path on the
remote machine where rsync is installed

You may echo find the command:

	rsh samba 'echo $PATH'

for determining what your remote path is.



spaces in filenames


Jim wrote:
> This seems to imply rsync can't copy files with names containing
> spaces.  A couple quick greps through the man page suggests that
> this limitation isn't mentioned.

Short answer: rsync can handle filenames with spaces

Long answer: 

rsync handles spaces just like any other unix command line application.
Within the code spaces are treated just like any other character so
a filename with a space is no different from a filename with any
other character in it.

The problem of spaces is in the argv processing done to interpret the
command line. As with any other unix application you have to escape
spaces in some way on the command line or they will be used to
separate arguments. 

It is slightly trickier in rsync because rsync sends a command line
to the remote system to launch the peer copy of rsync. The command
line is interpreted by the remote shell and thus the spaces need
to arrive on the remote system escaped so that the shell doesn't
split such filenames into multiple arguments.

For example:

	rsync -av fjall:'a long filename' /tmp/

won't work because the remote shell gets an unquoted filename. Instead
you have to use:

	rsync -av fjall:'"a long filename"' /tmp/

or a similar construct (there are lots of varients that work).

As long as you know that the remote filenames on the command line
are interpreted by the remote shell then it all works fine. 

I should probably provide the above examples in the docs :-)

Cheers, Andrew



stderr & stdout


> Why does rsync produce some things on stdout and some on stderr?

All messages which originate from the remote computer are sent to stderr.
All informational messages from the local computer are sent to stdout.
All error messages from the local computer are sent to stderr.

There is a reason to this system, and it would be quite difficult to change.
The reason is that rsync uses a remote shell for execution. The remote
shell provides stderr/stdout. The stdout stream is used for the rsync 
protocol. Mixing error messages into this stdout stream would involve
lots of extra overhead and complexity in the protocol because each message
would need to be escaped, which means non-messages would need to be encoded
in some way. Instead rsync always sends remote messages to stderr. This means
they appear on stderr at the local computer. rsync can't intercept them.

If you have a problem with scripts or cron jobs that produce stderr then I
suggest you use your shell to redirect stderr to stdout. For example you
could do a cron line like this:

0 0 * * * /usr/local/bin/rsync -avz /foobar /foo 2>&1 > logfile

this would send both stderr and stdout to "logfile". The magic
bit is the "2>&1" which says to redirect stderr to stdout.




subscribe


> How to subscribe to rsync mailing list?

Send a email to listproc@samba.org with no subject and a
body of "subscribe rsync Your Name"

See http://lists.samba.org/ for more info.





=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=