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The Apache HTTP Server is an efficient, extensible web server. It is one of the most popular web servers used the Internet.


When updating between Apache versions, check the Upgrade guide.

USE flags

USE flags for www-servers/apache The Apache Web Server

apache2_modules_access_compat Group authorizations based on host (name or IP address). Available as a compatibility module with previous versions. local
apache2_modules_authn_core Provides core authentication capabilities common to all authentication providers (functionality provided by authn_alias in previous versions). local
apache2_modules_authz_core Provides core authorization capabilities to various authorization/authorization modules, such as authn_file and authz_user. local
apache2_modules_authz_dbd Provides authorization capabilities via SQL database so that authenticated users can be allowed or denied access to portions of the web site by group membership. local
apache2_modules_cache_disk Disk based storage module for the HTTP caching filter (similar to mem_cache in previous versions). local
apache2_modules_cache_socache Shared object cache (socache) based storage module for the HTTP caching filter. local
apache2_modules_http2 Enable http2/alpn module local
apache2_modules_lbmethod_bybusyness Pending request counting load balancer scheduler algorithm for proxy_balancer. local
apache2_modules_lbmethod_byrequests Request counting load balancer scheduler algorithm for proxy_balancer. local
apache2_modules_lbmethod_bytraffic Weighted traffic counting load balancer scheduler algorithm for proxy_balancer. local
apache2_modules_lbmethod_heartbeat Heartbeat traffic counting load balancer scheduler algorithm for proxy_balancer. local
apache2_modules_macro Macros for the Apache config file. local
apache2_modules_proxy_fcgi FCGI support module for mod_proxy. local
apache2_modules_proxy_html Module to rewrite links in html pages behind a reverse proxy local
apache2_modules_proxy_wstunnel Provides support for the tunnelling of web socket connections to a backend websockets server. local
apache2_modules_ratelimit Ratelimit module for transfer rate management local
apache2_modules_remoteip Remotip module for logging local
apache2_modules_slotmem_shm Slot-based shared memory provider. local
apache2_modules_socache_shmcb A shared object cache provider using a high-performance cyclic buffer inside a shared memory segment. local
apache2_modules_unixd Basic (required) security for Unix-family platforms. local
debug Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces global
doc Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally global
ldap Add LDAP support (Lightweight Directory Access Protocol) global
libressl Use dev-libs/libressl as SSL provider (might need ssl USE flag), packages should not depend on this USE flag global
selinux !!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur global
ssl Add support for Secure Socket Layer connections global
static Link in apache2 modules statically rather then plugins local
suexec Install suexec with apache local
threads Add threads support for various packages. Usually pthreads global


If you want to use the Apache event MPM, then add the following to make.conf:

FILE /etc/portage/make.confApache event MPM

If you want to use the Apache worker MPM, then add the following to make.conf:

FILE /etc/portage/make.confApache worker MPM

And, enable the Apache threads USE flag:

FILE /etc/portage/package.useApache threads support
www-servers/apache threads

Then emerge Apache:

root #emerge --ask www-servers/apache

Global support

Enabling the apache2 global USE flag provides support for Apache in other packages. This may cause www-servers/apache to be installed automatically if a package depending on Apache has been emerged.

FILE /etc/portage/make.confAdding Apache to system USE flags

After configuring USE variables, update the system so the changes take effect:

root #emerge --ask --changed-use --deep @world



There are two main files that configure Apache2's behavior on the system:

  • Gentoo's Apache2 init script configuration file /etc/conf.d/apache2
  • Apache2 server's conventional configuration file /etc/apache2/httpd.conf


The apache2 file located in /etc/conf.d is Gentoo's init script configuration file. The only active line in this file is the APACHE2_OPTS variable line:

FILE /etc/conf.d/apache2

This line defines options that will be interpreted by the various configuration files using the <IfDefine option-name> statement to activate or deactivate some part of the whole configuration. This will be returned to later in the article.


The httpd.conf file is Apache server's conventional configuration file. In fact this file is only an entry point for configuration. The whole configuration is split in many files in the /etc/apache2/ directory, that are assembled together using the Include directive. For example, the statement Include /etc/apache2/modules.d/*.conf, in httpd.conf, aims at including all the files in /etc/apache2/modules.d/ which name ends with .conf.

Taking into account what has been said in the subsection above, and as module configuration files (files in /etc/apache2/modules.d) almost always start with the <IfDefine module-name>, the content of one file inside /ect/apache2/modules.d, will ONLY be assembled with the rest of the configuration, if the matching option is set using a -D module-name flag in the APACHE2_OPTS variable in the /etc/conf.d/apache2 file. The 00_default_settings.conf configuration file is an exception to this rule as it doesn't start with an IfDefine statement and therefore is always included in the resulting configuration.


After a fresh install of an Apache server, the configuration resulting from the assemblage of the different configuration files is as follows. Start with the entry point /etc/apache2/httpd.conf.

This is only given for quick reference and to give an overall view. Users are strongly invited to review the comments included in the various files to understand the ins and out of the configuration. Please also refer to the Apache manual for an in depth understanding of Apache configuration.
FILE /etc/apache2/httpd.conf
ServerRoot "/usr/lib64/apache2"
#Module loaded unconditionally, assuming the USE flag is no unset in
# /etc/portage/make.conf or in /etc/portage/package.use
LoadModule actions_modulemodules/mod_actions.so
#other modules loaded that way : alias_module, auth_basic_module, authn_alias_module,
# authn_anon_module, authn_dbm_module, authn_default_module, authn_file_module, 
# authz_dbm_module, authz_default_module, authz_groupfile_module, authz_host_module, 
# authz_owner_module, authz_user_module, autoindex_module,  cgi_module,  cgid_module, 
# deflate_module, dir_module, env_module, expires_module, ext_filter_module, filter_module,
#  headers_module, include_module,  log_config_module, logio_module, mime_module,  
# mime_magic_module, negotiation_module, rewrite_module, setenvif_module, 
# speling_module,ssl_module, status_module, unique_id_module, usertrack_module, host_alias_module
#Modules loaded conditionally, assuming matching USE flag is not unset in
# /etc/portage/make.conf or in /etc/portage/package.use (flag to be set in )
LoadModule authnz_ldap_module modules/mod_authnz_ldap.so
#other modules loaded that way : cache_module, dav_module, dav_fs_module,
# dav_lock_module,disk_cache_module,  file_cache_module, info_module, ldap_module,
# mem_cache_module, userdir_module
User apache
Group apache
# Supplemental configuration
#this part is included via Include /etc/apache2/modules.d/*.conf 
#included from /etc/apache2/modules.d/00_default_settings.conf-------------v
#this is always included as there is not option to deactivate it.
Timeout 300
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 15
UseCanonicalName Off
AccessFileName .htaccess
ServerTokens Prod
TraceEnable off
ServerSignature On 
HostnameLookups Off
EnableMMAP On
EnableSendfile On
FileEtag INode MTime Size
ContentDigest Off
ErrorLog /var/log/apache2/error_log
LogLevel warn
<Directory />
	Options FollowSymLinks
	AllowOverride None
	Require all denied
<IfModule dir_module>
	DirectoryIndex index.html index.html.var
<FilesMatch "^\.ht">
	Require all denied
#included from 00_mod_info.conf--------------------------------------------v
<IfDefine INFO>
<Location /server-info>
	SetHandler server-info
	Require host
#included from 00_languages.conf
# Settings for hosting different languages.
	AddLanguage ca .ca
	AddLanguage zh-TW .zh-tw
	LanguagePriority en ca cs da de el eo es et fr he hr it ja ko ltz nl nn no pl pt pt-BR ru sv zh-CN zh-TW
	ForceLanguagePriority Prefer Fallback
	AddCharset us-ascii.ascii	.us-ascii
	AddCharset ISO-8859-1		.iso8859-1 .latin1
	AddCharset shift_jis		.shift_jis .sjis
#this part is included via Include /etc/apache2/vhosts.d/*.conf 
#from 00_default_ssl_vhost.conf-----------------------------------------------------vv
<IfDefine SSL>
		<IfModule ssl_module>
			Listen 443
			<VirtualHost _default_:443>
				ServerName localhost
				# this part is included via Include /etc/apache2/vhosts.d/default_vhost.include
				ServerAdmin root@localhost
				DocumentRoot "/var/www/localhost/htdocs"
				<Directory "/var/www/localhost/htdocs">
	   				Options Indexes FollowSymLinks
	   				AllowOverride All
	   				Require all granted
				<IfModule alias_module>
	   				ScriptAlias /cgi-bin/ "/var/www/localhost/cgi-bin/"
				<Directory "/var/www/localhost/cgi-bin">
	   				AllowOverride None
	   				Options None
	   				Require all granted
        			#end of Include ---------------------------^
				ErrorLog /var/log/apache2/ssl_error_log
				<IfModule log_config_module>
					TransferLog /var/log/apache2/ssl_access_log
				SSLEngine on
				SSLCertificateFile /etc/ssl/apache2/server.crt
				SSLCertificateKeyFile /etc/ssl/apache2/server.key
				<FilesMatch "\.(cgi|shtml|phtml|php)$">
					SSLOptions +StdEnvVars
				<Directory "/var/www/localhost/cgi-bin">
					SSLOptions +StdEnvVars
				<IfModule setenvif_module>
					BrowserMatch ".*MSIE.*" \
					nokeepalive ssl-unclean-shutdown \
					downgrade-1.0 force-response-1.0
				<IfModule log_config_module>
					CustomLog /var/log/apache2/ssl_request_log \
					"%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
#from 00_default_vhost.conf-------------------------------------------------------vv
	Listen 80
	NameVirtualHost *:80
	<VirtualHost *:80>
		ServerName localhost
		# this part is included via Include /etc/apache2/vhosts.d/default_vhost.include
		ServerAdmin root@localhost
		DocumentRoot "/var/www/localhost/htdocs"
		<Directory "/var/www/localhost/htdocs">
	   		Options Indexes FollowSymLinks
	   		AllowOverride All
	   		Require all granted
		<IfModule alias_module>
	   		ScriptAlias /cgi-bin/ "/var/www/localhost/cgi-bin/"
		<Directory "/var/www/localhost/cgi-bin">
	   		AllowOverride None
	   		Options None
	   		Require all granted
        	#end of Include -----------------------------------------------^
		<IfModule mpm_peruser_module>
			ServerEnvironment apache apache
# end of include ****************************************************************************************^^^

First sign of life

As visible in the initial configuration above, the pre-installed virtual host's DocumentRoot directory is /var/www/localhost/htdocs, its server name is localhost. In addition an index.html file is provided in the DocumentRoot directory, thus to check whether everything is correctly installed or not, point a browser to http://localhost/.

An "It works!" message should be printed on the page.

Out of the box, Firefox has a feature designed to help users who mis-typing URLs in the browser bar. If a URL fails to resolve, Firefox tries a couple of alterations of the URL to try find what the user 'might have' really intended, appending a .com or prefixing a www. to the host name portion of the URL to see if they resolve.

This feature, which was introduced in the early versions of Firefox, is somewhat annoying for developers. The feature means that when a server running on localhost fails to respond, Firefox decides to try localhost.com or www.localhost.com. This often resolves to a not found page.

To disable this feature:

  1. Enter about:config in the browser bar
  2. Click "I'll be careful" and enter the special configuration page
  3. Enter browser.fixup.alternate.enabled in the search box that appears
  4. Right click on the browser.fixup.alternate.enabled that appears in the filtered list below and choose toggle to set the value to false.

Enabling mod_security

Install www-apache/mod_security:

root #emerge --ask www-apache/mod_security

Enable the SECURITY module in the apache2 file's APACHE2_OPTS variable:

FILE /etc/conf.d/apache2Enabling the security module

Control this module by editing /etc/apache2/modules.d/79_modsecurity.conf and /etc/apache2/modules.d/80_modsecurity-crs.conf files, then restart Apache.

Enabling PHP support

Install PHP with the apache2 USE flag and enable the module:

With >=app-eselect/eselect-php-0.8.1, the APACHE2_OPTS variable changed to -D PHP instead of -D PHP5. This allows for future major versions to flow smoothly.
FILE /etc/conf.d/apache2Enabling the PHP module

Before testing if the PHP module works, check that the file /etc/apache2/modules.d/70_mod_php.conf exists and contains the following definition:

FILE /etc/apache2/modules.d/70_mod_php.confVerifying the PHP module will be loaded
<IfDefine PHP>
	# The mod_php.so symlink is controlled by
	# eselect-php. However, the module name changed from
	# php5_module to php7_module so we can't blindly load whatever
	# is there. Instead we let eselect-php manage a small
	# configuration file that loads the appropriate module.
	# This is relative to ServerRoot (see httpd.conf).
	Include ../../../var/lib/eselect-php/mod_php.conf
	# Tell apache that mod_php should handle PHP files.
	# NOTE: Avoiding AddHandler/AddType for security (bug
	# #538822). Please read the related news item!
	<FilesMatch "\.(php|php[57]|phtml)$">
		SetHandler application/x-httpd-php
	# PHP source files which are meant to be displayed as
	# syntax-highlighted source code.
	<FilesMatch "\.phps$">
		SetHandler application/x-httpd-php-source
	DirectoryIndex index.php index.phtml

If it does not exist create it.

To verify the PHP module works, create a test page:

FILE /var/www/localhost/htdocs/index.phpPHP test page
  <?php phpinfo(); ?>

Now, suppress or rename /var/www/localhost/htdocs/index.html and open the test page: http://localhost/

A table describing the PHP settings should be visible.

Modify PHP versions

To change the version of PHP handled by Apache, first list the available versions for the apache2 Server Application Programming Interface (SAPI):

root #eselect php list apache2
 [1]   php5.3
 [2]   php5.4 *
 [3]   php5.5

Change it to the version of choice:

root #eselect php set apache2 N

Substitute N in the example above to the requested number in the output of eselect php list apache2 as displayed earlier on.

Virtual hosts

For each virtual host, provide a DocumentRoot directory that is reachable and accessible by the Apache daemon. Add a virtual host configuration file (VirtualHost.conf) in the /etc/apache2/vhosts.d directory which uses this DocumentRoot and the virtual host server name. Do not forget to add an entry for this domain name in /etc/hosts.

To assign the apache user/group ownership on the virtual host files, use chown like in the following example:

root #chown apache:apache /var/www/sitename

Below are two example virtual host definitions, one for domainname1.com and one for domainname2.com. Notice the different DocumentRoot and ServerName directives even though the host itself (*:80) remains the same:

CODE Example virtual host definitions
<VirtualHost *:80>
    ServerAdmin email@site.com
    DocumentRoot /var/www/website1
    ServerName domainname1.com
<VirtualHost *:80>
    ServerAdmin email@site.com
    DocumentRoot /var/www/website2
    ServerName domainname2.com

It is recommended to provide an IP based virtual host definition as well. This allows the administrator to put up a message for users that try to reach a site through its IP address:

CODE IP-based virtual host
<VirtualHost *:80>
    ServerAdmin email@site.com
    DocumentRoot /var/www/html
    ServerName xxx.xxx.xxx.xxx

After inserting virtual hosts, the server needs to be (gracefully) restarted for the new sites to become active.

Enabling PHP through fcgid

Install www-apache/mod_fcgid and dev-lang/php. The PHP package requires cgi to be set as a USE flag:

root #emerge --ask www-apache/mod_fcgid dev-lang/php

Edit the mod_fcgid.conf file:

FILE /etc/apache2/modules.d/20_mod_fcgid.conf
<IfDefine FCGID>
LoadModule fcgid_module modules/mod_fcgid.so
SocketPath /var/run/fcgidsock
SharememPath /var/run/fcgid_shm
AddHandler php-fcgid .php
AddType application/x-httpd-php .php
Action php-fcgid /fcgid-bin/php-fcgid-wrapper
# max request 128mb
FcgidMaxRequestLen 134217728
<Location /fcgid-bin/>
        SetHandler fcgid-script
        Options +ExecCGI

Create the needed directory:

root #mkdir /var/www/localhost/htdocs/fcgid-bin

Symlink it for the PHP wrapper:

root #ln -s /usr/bin/php-cgi /var/www/localhost/htdocs/fcgid-bin/php-fcgid-wrapper

Enable the FCGID module:

FILE /etc/conf.d/apache2Enabling the fcgid module

Finally restart Apache and check the phpinfo() site created earlier. The value of Server API should be CGI/FastCGI

Enabling PHP-FPM through mod_proxy_fcgi in Apache 2.4

The following pre-requisites must be satisfied to enable PHP-FPM through mod_proxy_fcgi:

  • >= PHP 5.3
  • >= Apache 2.4

Furthermore, there are a few restrictions on the availability of functionality within Apache 2.4:

The following configuration will only work with Apache 2.4.10 and newer. It relies on the FilesMatch directive and be placed within the main server config or VirtualHosts. The location of the UNIX socket is determined by the listen directive in the php-fpm.conf configuration file, allowing for specifying separate pools per site or function.

In the following example, FilesMatch is placed within the PHP module config file of Apache:

FILE /etc/apache2/modules.d/70_mod_php.confUsing PHP-FPM (recommended for Apache 2.4.10 and newer)
<IfDefine PHP>
        <FilesMatch "\.php$">
                SetHandler "proxy:unix:/var/run/php-fpm/www.sock|fcgi://localhost"
	# Set it to handle the files
	<IfModule mod_mime.c>
		AddHandler application/x-httpd-php .php .php5 .phtml
		AddHandler application/x-httpd-php-source .phps
	DirectoryIndex index.php index.phtml

Or, you can use ProxPassMatch -- the only option if the Apache version is between 2.4.0 and 2.4.8, inclusive.

FILE /etc/apache2/modules.d/70_mod_php.confUsing PHP-FPM (recommended for Apache 2.4.8 and older)
<IfDefine PHP>
        # Send all requested PHP files to PHP-FPM via fcgi://PHP_FPM_LISTEN_ADDRESS:PHP_FPM_LISTEN_PORT/DOCUMENT_ROOT/$1
        ProxyPassMatch ^/(.*\.php)$ fcgi://$1
	# Set it to handle the files
	<IfModule mod_mime.c>
		AddHandler application/x-httpd-php .php .php5 .phtml
		AddHandler application/x-httpd-php-source .phps
	DirectoryIndex index.php index.phtml

By default the listen directive is not set to a socket. First create the directory for the socket file:

root #mkdir /var/run/php-fpm

Next, update the php-fpm.conf file as follows:

FILE php-fpm.confUpdating listen directive
; Set permissions for unix socket, if one is used. In Linux, read/write
; permissions must be set in order to allow connections from a web server. Many
; BSD-derived systems allow connections regardless of permissions.
; Default Values: user and group are set as the running user
;                 mode is set to 0666
listen.owner = nobody
listen.group = nobody
;listen.mode = 0666
 ; The address on which to accept FastCGI requests.
 ; Valid syntaxes are:
 ;   'ip.add.re.ss:port'    - to listen on a TCP socket to a specific address on
 ;                            a specific port;
 ;   'port'                 - to listen on a TCP socket to all addresses on a
 ;                            specific port;
 ;   '/path/to/unix/socket' - to listen on a unix socket.
 ; Note: This value is mandatory.
 ;listen =
listen = /var/run/php-fpm/www.sock

Then enable both the PHP and PROXY modules:

FILE /etc/conf.d/apache2Enabling PHP and proxy modules




Start the Apache server:

root #/etc/init.d/apache2 start

Add Apache to the default runlevel:

root #rc-update add apache2 default

Restart the Apache service:

root #/etc/init.d/apache2 restart

Reload Apache configuration files:

root #/etc/init.d/apache2 reload


Start the Apache server:

root #systemctl start apache2

Add Apache to the default runlevel:

root #systemctl enable apache2

Restart the Apache service:

root #systemctl restart apache2



The Apache server can be difficult to configure properly. Below are some resources that may be helpful when issues occur:


Verifying IP interfaces and ports on which Apache2 is running on and listening to:

root #netstat -tulpen | grep apache
tcp     0     0*     LISTEN     0     10932720     4544/apache2        
tcp     0     0*     LISTEN     0     10932716     4544/apache2        

Testing if a connection to a Apache server is working on localhost:

user $telnet localhost 80
Connected to localhost.
Escape character is '^]'.

Interrupt the connection test with Ctrl+c and Enter.

apr_sockaddr_info_get() failed for <System_Hostname>


apache2: apr_sockaddr_info_get() failed for System_Hostname


When this occurs, add the host name to the /etc/hosts file:

FILE /etc/hostsAdding a Hostname for Apache localhost System_Hostname

See also

  • Lighttpd - A fast, lightweight web server.
  • Nginx - A small, robust, and high-performance HTTP server and reverse proxy.

External resources