<snip> "Multisite" means multiple sites installed on a single codebase. You have to have a base installation and that is where the VirtualHost will point. ? Nancy </snip>
Thank you Nancy The fault was not the base installation but the way I named the test multi site. example.com did not work, apparently because there is a web page on a domain called example.com but example1.ab and example2.xy did work well as a multi site on my home pc. It is a bit misleading in the Drupal.org tutorial which uses example.com in a number of places as examples for multi site installation.
So now it works on my home Fedora 16 box but I have no luck getting it to work on the ISP's remote centos shared server where I cannot access nor change httpd.conf, and /etc/hosts does not exist. Increasingly I find it a pity that apache has to be altered when the redirection and access could instead be through /sites.php which in this case seems to have no effect, or I am not understanding the instructions.
That sites.php in the /sites folder seems correct but Drupal seems to ignore it no matter what I put on the last line as per instructions. Whatever! It seems that http.conf and /etc/hosts has to be altered and I cannot find out how in cpanel or ssh on a shared server.
I wonder how others in similar situations have achieved multi sites on shared server? thanks Roger