Shortcuts
Run Apache in Docker (for testing)
$ docker run -dit --name my-apache-app -p 8090:80 -v "$PWD":/usr/local/apache2/htdocs/ httpd:2.4
Apachectl
$ sudo apachectl status
$ sudo apachectl start
$ sudo apachectl stop # sudden stop, drops current connections
$ sudo apachectl graceful-stop # serve whatever that's currently serving and then drops
$ sudo apachectl restart # parent doesn't get killed, only children gets killed
$ sudo apachectl graceful # similar to restart but graceful
$ sudo apachectl reload # reload apache
The above commands can be replaced with systemd counterparts:
$ sudo systemctl status apache2
$ sudo systemctl stop apache2
$ sudo systemctl restart apache2
Additionally, one can use httpd -k command,
$ sudo httpd -k restart
$ sudo httpd -k stop
$ sudo httpd -k graceful
Configuration location
Depends on the server and Linux, the configuration location varies. On Debian-based distro, the config file is either on:
$ /usr/local/apache2/conf/httpd.conf
$ /etc/apache2/apache2.conf
If none worked, an easier way to find out is:
$ apachectl -V
Which prints information about Apache and its configuration location.
Changes in the configuration can be tested by:
$ apachectl -t
Log files
Apache error log configurations are defined in the ErrorLog directive. Usually when inspecting the apache2.conf, you see something like,
ErrorLog ${APACHE_LOG_DIR}/error.log
The ${APACHE_LOG_DIR} is an Apache environment variable which is set in envvars file. Inspecting that should give exact address of log files.
Under Debian based distribution, the location is /var/log/apache2.
The LogLevel directive controls the verbosity of the log. Complete list is here. The default is warn.
To customize log for each virtual host, one can open /site-availables/*.conf file and define log directives. For example,
ErrorLog ${APACHE_LOG_DIR}/test-error.log
LogLevel info
CustomLog ${APACHE_LOG_DIR}/test-access.log combined
Apache directive
A directive is an instruction that tells Apache what to do. It is one per line. A list of all directive can be found here.
One important directive is DocumentRoot which determines the location that Apache serves files from,
DocumentRoot "/usr/local/apache2/docs/dummy-host2.example.com"
Apache configuration can be overriden in the .htaccess file making main Apache config needless. What confiugration can be overriden inside of .htaccess is determined by the main Apache config. Changes on .htaccess file is immediate, and do not require any reload or restart.
.htaccess in general are not recommended due to security complications and slowness since for each request, the file is read and apply the configuration.
Virtual hosting
Apache allows to server multiple domains from the same server. It is the concept used by the shared hosting platforms.
To list down all the configured virtual host:
$ apachetl -t -D DUMP_VHOSTS
Apache modules
There are two types of modules:
- Static: compiled into the Apache (included when compiling the program)
- Shared: dynamically loaded and do not require compilation, provides flexibility but slower
Modules have directives. To ensure Apache functions if a module is not present, it is a good idea to wrap the needed functionality in the IfModule syntax:
<IfModule mod_xyz.c>
</IfModule>
To get list of all modules,
$ apachectl -t -D DUMP_MODULES
On Debian modules are enabled and disabled by a2enmod and a2dismod which underneath creates and remove symlinks /etc/apache2/mods-enabled. All modules are available under /etc/apace2/mods-available.