The httpd.conf file is a configuration file used by the Apache webserver. It contains information about settings and functions by this webserver. The file can be located in various places; this depends on the version of Apache and/or the operating system used. It can be commonly found here: /etc/httpd/httpd.conf

You can then edit this file with this command:

sudo nano /etc/httpd/httpd.conf

However, in case this file can not be found on the location indicated as above, you can perform this command:

httpd -V

The output of this command should reveal the location of httpd.conf on your Linux apache webserver.