Understanding Apache web server configuration files

Apache webserver reads its configuration files every time it's started. The configuration files are in plain text format, and Apache will need to restart every time there are changes in the configuration file for the changes to take effect.

Apache's primary configuration file location is set during compilation and is set differently between distributions. The configuration is usually split into multiple files for ease of management and separation of concern. It will then be called from the main configuration file using Include and IncludeOptional directives.

You can always check the location of the primary configuration file by running the Apache binary for your distribution with the -V option and then looking for the SERVER_CONFIG_FILE value.

$ apachectl -V
Server version: Apache/2.4.41 (Unix)
Server built:   Nov  9 2019 07:53:54
Server's Module Magic Number: 20120211:88
Server loaded:  APR 1.5.2, APR-UTIL 1.5.4
Compiled using: APR 1.5.2, APR-UTIL 1.5.4
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_FLOCK_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/usr"
 -D SUEXEC_BIN="/usr/bin/suexec"
 -D DEFAULT_PIDLOG="/private/var/run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/private/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

The location of Apache's main configuration file is different for most distributions, and they are also split differently. The following table lists how the configuration file is managed for different distributions:

Apart from using a different location for the main configuration file, different distributions also use different values for Apache configuration options.

The table below lists some of the default configuration values for Apache on different distributions.