I've two WordPress blogs running on a single server, so that they both have the same file system. Both blogs make use of the same template, which template is copied within each theme directory. Each time which i update the theme I have to copy within the new files to both theme sites.

Can you really have these two blog share a typical theme directory to ensure that I only have to modify one template folder?

Absolutely. Just make certain they have read use of that shared folder.

Then setup a symlink from each one of the theme folders. You need to do this with ln -s

If you cannot use symbolic links, after that you can setup a rewrite-rule, which redirects all demands from /wordpress-content/styles to love /var/www/shared/styles.

If you would like, I'm able to offer an example.

Another approach, if using source control (SVN, Git), is always to checkout the theme in to the two locations increase them.

You'll have a symlink link one theme folder to a different.

remove among the theme folders and employ ln like clubpenguin

ln -s <source> <dest>