app works when copied with tar, not with rsync

Matt McCutchen matt at
Sat Dec 29 21:33:12 GMT 2007

On Thu, 2007-12-27 at 17:52 -0500, Brian Poole wrote: 
> I'm experiencing a most unusual problem.. I am copying a directory
> from one server to another (both Solaris 10/SPARC). No applications
> are using the directory in question on either side while the copy is
> in progress. After the copy successfully completes (no errors or
> warnings), my user brings up the application (mix of binaries, java
> files, and Apache Tomcat servlets) contained in this directory on the
> new server. Or at least, they try to..
> If I use rsync to perform this copy (tested with 2.5.5 and 3.0.0pre7),
> the application logs an unusual Java error (reproduced near the
> bottom) and dies. Surely an application issue, right?
> Well, it turns out, that if I use GNU tar (and I must use GNU tar as
> the directory has very long file names) to copy the same set of files,
> the application works without issue after being copied... Hmm..

I can think of one potential difference between rsync and tar results
that you haven't mentioned: the order of entries within each directory.
You can see the order with "ls -U".  Some filesystems, such as ext2,
tend to leave directory entries in the order they were originally
created.  Others, such as reiserfs, seem to automatically sort the
entries in such a way that two directories containing the same names
always read in the same order.  On a filesystem of the first kind, tar
will tend to give you a destination with the same entry order as the
source, while rsync sorts the entries to some extent.

It is conceivable that your application needs the directory entries to
be in a certain order to work correctly.  (Of course, such a dependency
constitutes a bug.)  The way I can see this happening for a Java
application is if it uses a classpath entry of the form dir/* (to match
any number of jars in the directory) and multiple jars provide
identically named classes.  In my tests with Sun's Java 1.6.0_02 on
Linux, the application gets the class from the jar that comes first in
the directory; if rsync reorders the directory, the application may get
the wrong class.  If this is indeed the problem, there isn't much you
can do except report the bug and use tar in the meantime.


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