People use Eclipse. People use Windows. People use these tools together to develop code. I am not (typically) one of these people. My development environment is usually either Coda on the Mac or vim on the command line. But I do work with people using Eclipse on Windows, and while the code we’re building together is not platform specific, it does help if we all have the same capabilities. So when I added some functionality to our Apache ant deploy script to synchronize files on a remote server using rsync, the next step was, of course, getting it to work on Windows.

Allow me to walk through the configuration, step-by-step. The first thing was to create a target in my build.xml file which ant can use to synchronize files to the remote machine. Something like this:

<target name="rsync_remotehost" >
   <exec executable="rsync" dir="${cfg.someDir}">
        <arg line="-aOvz --chmod=g+w,Da+rX,Fa+r,F-X --exclude .svn . \
            ${rsync.user}@${rsync.server}:${rsync.dir}" />
    </exec>
</target>

So really, all that does is define a target which runs rsync inside a specified directory. The important aspects to note are the rsync parameters. For example this: -aOvz These are pretty standard options (a for archive, v for verbose, z does compression), except for the O. I wasn’t used to using this option, but it’s important for a very subtle reason. To explain, first a little background. Typically when I want to synchronize the entire contents of a directory with rsync, I would do this:

rsync -avz path/to/somedir user@remote.host:/some/remote/dir

But this doesn’t quite work in the Eclipse+Ant environment on Windows. The reason is because the variables holding the directory locations get represented in Windows path notation. (Imagine a C: at the beginning and all the directory slashes are backwards.) Rsync can’t handle this. It’s a Unix-based tool. It’s expecting a Unix-style path. So to get around this we set a dir attribute in the exec element which causes ant to change to that directory before execution. We also use a ‘.’ in the rsync argument line to specify that the source contents are this directory. This has an odd side effect: rsync attempts to set times on the corresponding directory at the remote location, which tends to fail. So we use the -O option to tell rsync not to set times on directories.

The other arguments given to rsync are for specifying more sane permissions on the remote files since Windows wanted to kill all permissions for group and world by default (--chmod=g+w,Da+rX,Fa+r,F-X) and for excluding our local Subversion files (--exclude .svn).

So that’s the ant target. Now to the interesting parts. First we have to get rsync installed on Windows. Cygwin makes this relatively easy. Download and install. Most options are pretty much good at the defaults, except watch out for this screen:

On this screen you need to add a couple of packages, both in the Net section: Net -> rsync and Net -> openssh. Just click once on each of those packages and it will add what you need. Finish up the installation by clicking on ‘Next’ and ‘Finish’.

Once Cygwin and Rsync is installed, there’s still a few more things we need to do in order to get it all to work together correctly. First, you need to add the path to Cygwin’s binaries to the Windows path so that system calls in Eclipse will find the Cygwin binaries. To do that, right-click on ‘My Computer’ and click ‘Properties’. Then click on the ‘Advanced’ tab and then the ‘Environment Variables’ button:

Next find the section on the bottom called ‘System variables’ and scroll down and double-click on the ‘Path’ line:

Insert the following at the end of the ‘Variable value’ line:

;%SystemDrive%\cygwin\bin

Lastly, you need to set up a public key so that when ant runs, it won’t hang waiting for you to input a password (which you can’t do inside Eclipse anyway). To do that, open up Cygwin – you should have a shortcut on your desktop. When it opens run:

ssh-keygen

Accept the defaults, don’t add a passphrase, just hit enter instead. When the command is done, it will have saved a public and private key for you. We want to upload those to our remote server, like so (you’ll be asked for your password, and possibly to accept the key for the remote host – type ‘yes’ to do so):

scp ~/.ssh/id_rsa.pub user@remote.host:~/

Next we need to place it somewhere special on the remote host (you’ll be asked for your remote password again):

ssh user@remote.host
install -dv ~/.ssh
chmod 0700 ~/.ssh
cat id_rsa.pub >> ~/.ssh/authorized_keys
rm id_rsa.pub
exit

Now, test the connection to make sure that you can connect without giving a password:

ssh user@remote.host

If all is good just exit and that should be it! The next time you open up Eclipse, it should be able to call rsync and run successfully through your Ant target!