Failed Apache2 start, no error log

Question

I would restart Apache2 but there comes an Error

$ sudo service apache2 start

Starting web server apache2

Action \'start\' failed.
The Apache error log may hav         


        

Answer 1

If we have no entries in log files then we can try to debug apache2 using this command:

$ apache2 -S

or

$ apache2 -e debug

Possible output:

[Fri Apr 05 04:04:59.682880 2019] [core:warn] [pid 11086] AH00111: Config variable ${APACHE_RUN_DIR} is not defined
apache2: Syntax error on line 80 of /etc/apache2/apache2.conf: DefaultRuntimeDir must be a valid directory, absolute or relative to ServerRoot