How can I prevent the vServer User from seeing everything of the whole server

I use the SSH Secure Shell for Workstations (SSH2 client), if I login per ftp, I can see everything of the whole server, including all root files on the whole server, how can I prevent that?

It is a big problem.

Many thanks in advance

Furthermore, how can I create subdomain, and install some programm, for example mail programm like squirrel under that subdomain?

when logging in over ssh you can see not all files, though one can scroll through most folders.
It is a charactaristic off ssh. One can do nothing with those files and never see sensitive information or write over them. It has been that way always.

subdomains: you can create a server and then create them either as subserver or as a top level server.

squirrel can be installed through the install scripts. or on GPL version, you can download it from their website, upload on your server and run the installationprocess described in their documentation.

many thanks, Ronald, I think I can set up a subserver for the sub domain, then use Iframe to include the /mail/index.php