Apache user on ISPconfig (SUSE 10)

[nox171]

Hi,
I'm installing Joomla on one of my ISPconfig's sites.

I'm following the guide Joomla CMS On An ISPConfig Server Within 10 Easy Steps

but when it says to change the permission to according apache to have access to the web folder I get stuck.

This is the command that the guide provide
( chown -R -v -f www-data:www-data web/* )
when I try to type it in, I receive an error:

chown: `www-data:www-data': invalid user

Do you know what is the right command for me?
I'm running ISPconfig under SUSE 10.0
I think my user for apache is different but I don't know which one I have to use...

Thanks