Hello Lisa.Google search suggestionhttp://httpd.apache.org/docs/2.2/vhosts/#directivesDutch_Master's post at Linux Format Forums
The command in XAMPP for Linux is httpd -S
not apache -S
I have lost touch with all things Linux but you could try this at a command line and change directory to /opt/lampp/bin
and type sudo ./httpd -S
- until this is corrected by a more knowledgeable XAMPP Linux user.
As I said, if your error is not critical in your VirtualHosts containers then the first (default) VirtualHost will be served and is a good indication something is wrong somewhere - so you must have a small syntax error in one or all of your VirtualHosts containers - the httpd -S
command results may reveal the problem.
If the error is critical then the server will not start and only then it is time to look in the error log file for clues - the non critical errors will not be written to the error log file because the server did not stop with an error.