You mentioned that you are using the FTP Layer.
Perhaps this is the symptom that you have some permission restriction on your server and perhaps that the symbolic links is not allowed.
See video 6 and 7 to check that
www.jms2win.com/en/tutorial#jms12x-6
www.jms2win.com/en/tutorial#jms12x-7

You also mentioned that you have a value in "open_basedir".
Can you tell us which HTTP server is used (cPanel, Plesk, Direct Admin, ...)
I suspect that you are using Plesk ?
I also suspect that you tried creating a slave site into a subdomain or a domain.

Did you tried creating a slave site into a subdirect like in video 9
www.jms2win.com/en/tutorial/259
Sample values:

* Site ID = slave1
* Domain name = {site_url}/multisites/{site_id}
* Deploy directory = {site_dir}

Your are right I'm using plesk with Ubuntu 8.04.

Symbolic link are supported and are created.

I did only try to install in in the multisite subdirectory.
The creation of a new installation will perform now correctly. The way as you suggested with slave1.
But with using my template and I assume, the only difference to use the DB from the master instead doing an new installation, the slave will use the configuration.php from the master instead the one from the slave. This slave I named test.
I did compare every file in the test and slave1 directory an I can't see any abnormal differences. If I would know where the mapping to the slaves configuration.php is lying it would help.

You get the master website when the domain name is not correctly spelled.
So check that the domain name is correctly written in the list of slave site.
Perhaps you have to define the domain with WWW and without WWW
It is also case sensitive.
Normally a domain name should always be written in lower case.

JMS search for an exact matching.
Also ensure that the slave site was successfully defined (blue message and not a red message).

I'm still the same problem. I can not perform patch. I even turned the FTP layer and hoping everything works out. Unfortunately it did not happen.
shows me this message:
"JFolder:: create: Infinite loop detected
Unable to create destination
Error during installation of the file "administrator / defines.php"

One or more backup file is missing. The original file (s) CAN NOT BE restore "

I still do not understand why my patch for Joomla!1.5 is works and Joomla! 1.6 is No works! I want to use Joomla! 1.6/1.7 (now I have 1.6.6).

Here is my configuration server (I have PHP 5.3)

I tried to contact support hosting. She told me that the problem is that JMS MULTI-SITE in Joomla! 1.6/1.7 does not work well with the parent directory. When I installed my Joomla! JMS and Web hosting to put on a subdirectory, so I really going to PATCH.
In Joomla! 1.5 This problem is not.
Please repair or for advice on what to do with it.
I do not want to install web sub-directory such as www.example.com/test but normally like www.example.com.

I use the latest version of JMS MULTI-SITE, as well as Joomla! 1.6.6, template from JoomlArt - Teline IV T3v2 framework, FTP Layer enabled, SAFE MODE ON (read more about the SAFE MODE on my webhost)

Thank you very much

Which JMS version do you use ?
The patch for Joomla 1.5, 1.6 and 1.7 are different.
See the change history to know if your JMS version is compatible with the Joomla version that you expect.
www.jms2win.com/en/faq/change-history-v12x

As Joomla themselve does not provide any ascending compatiblity and joomla 1.6 is NOT compatible with Joomla 1.5 and that Joomla 1.7 is NOT compatible with Joomla 1.6 then we have to develop specific patches for each joomla version.

Joomla require to migrate their joomla environment because they are not compatible with earlier version.

JMS is working for Joomla 1.6 or 1.7 if you have the latest version (1.2.62)
You will have to uninstall all the patches installed in Joomla 1.5 before upgrading your Joomla version.
You will also have to check that all the extension that you have installed in your Joomla are compatible with your future joomla version

JMS 1.2.62 is compatible with Joomla 1.5.23, 1.6.6, 1.7.0

I still can not patch. I deleted the existing installation of joomla (unfinished site, but I saved it on localhost) + database and I install clean installation Joomla 1.7.0 (from Joomla.org). I tried everything turned on and off layer. Result still the same. I can not patch. JMS I have the latest version, ie 1.2.62.
I still do not understand why I'm going to J1.5 and J.17 Sun Always it was a clean install of Joomla.
I think there will be a real bug in the form of JMS that works with J1.7 wrong with the parent directory, because when I give it to the subdirectories, everything goes. I tried all the tips you here in this thread sounded, but unfortunately without result.