How to find error in apache2.conf?

Question

Apache HTTP Server

After installing Cobbler (On a clean machine. aptitude install cobbler) Apache stopped working (asks to specify ServerName) tried to specify (in apache2.conf) both local ip and localhost and ip on the local network, but then apache simply does not start (no error)
In service apache2 status
Starting Apache httpd web server apache2
Action 'start' failed.
in error.log writes configuration failed
Question 1: why is ServerName needed? And what is the best way to write? (there is no real name, only ip)
Question 2: where else can I see information about the error, and how can I catch it (do not replace include config-enable/*.conf with a list of all files and discard 1 one by one) ?

Answer 1

try running apache configtest (may be a little different in your distro)
and show your apache2.conf