Apache HTTP Server

Related articles
XAMPP
/mod_perl
/mod_fcgid
/mod_gnutls
/mod_wsgi
The
Apache HTTP Server
, or Apache for short, is a very popular
web server
, developed by the Apache Software Foundation.
This article describes how to set up Apache and how to optionally integrate it with
PHP
.
Installation
Install
the
apache
package.
Configuration
Apache configuration files are located in
/etc/httpd/conf
. The main configuration file is
/etc/httpd/conf/httpd.conf
, which includes various other configuration files. The default configuration file should be fine for a simple setup. By default, it will serve the directory
/srv/http
to anyone who visits your website.
To run Apache,
start
httpd.service
. If everything is working correctly, visiting
http://localhost/
should display a simple index page.
For optional further configuration, see the following sections.
Advanced options
See the
full list of Apache configuration directives
and the
directive quick reference
.
These options in
/etc/httpd/conf/httpd.conf
might be interesting for you:
User http
For security reasons, as soon as Apache is started by the root user (directly or via startup scripts) it switches to this UID. The default user is
http
, which is created automatically during installation.
Listen 80
This is the port Apache will listen to. For Internet-access with router, you have to forward the port.
If you want to setup Apache for local development you may want it to be only accessible from your computer. Then change this line to
Listen 127.0.0.1:80
.
ServerAdmin you@example.com
This is the admin's email address which can be found on e.g. error pages.
DocumentRoot "/srv/http"
This is the directory where you should put your web pages.
Change it, if you want to, but do not forget to also change
<Directory "/srv/http">
to whatever you changed your
DocumentRoot
to, or you will likely get a
403 Error
(lack of privileges) when you try to access the new document root. Do not forget to change the
Require all denied
line to
Require all granted
, otherwise you will get a
403 Error
. Remember that the DocumentRoot directory and its parent folders must allow execution permission to others (can be set with
chmod o+x /path/to/DocumentRoot
), otherwise you will get a
403 Error
.
AllowOverride None
This directive in
<Directory>
sections causes Apache to completely ignore
.htaccess
files. Note that this is now the default for Apache 2.4, so you need to explicitly allow overrides if you plan to use
.htaccess
files. If you intend to use
mod_rewrite
or other settings in
.htaccess
files, you can allow which directives declared in that file can override server configuration. For more info refer to the
Apache documentation
.
Tip
If you have issues with your configuration you can have Apache check the configuration with:
apachectl configtest
More settings can be found in
/etc/httpd/conf/extra/httpd-default.conf
:
To turn off your server's signature:
ServerSignature Off
To hide server information like Apache and PHP versions:
ServerTokens Prod
User directories
User directories are available by default through
http://localhost/~yourusername/
and show the contents of
~/public_html
(this can be changed in
/etc/httpd/conf/extra/httpd-userdir.conf
).
If you do not want user directories to be available on the web, comment out the following line in
/etc/httpd/conf/httpd.conf
:
Include conf/extra/httpd-userdir.conf
Ensure that the Apache web server has sufficient permissions to traverse the user's home directory and access files within
~/public_html
. Directory traversal requires execute (
+x
) permission on each parent directory in the path, independent of the read (
r
) permissions on the target files.
The recommended method is to use
Access Control Lists
(ACLs) to grant access to the
http
user only:
$ setfacl -m u:http:x ~
$ setfacl -R -m u:http:rx ~/public_html
Avoid using world-executable permissions (e.g.
chmod o+x
), as this
weakens the security
of your home directory.
You also need to edit the configuration of the systemd service in the drop-in file
/etc/systemd/system/httpd.service.d/hardening.conf
[Service]
ProtectHome=no
Do a
daemon-reload
and
restart
httpd.service
to apply the changes. See also
Umask#Set the mask value
.
TLS
Warning
If you deploy
TLS
, be sure to follow
weakdh.org's guide
to prevent vulnerabilities. For more information see
Server-side TLS
.
Firstly
obtain a certificate
. If you own a public domain, you can use
Transport Layer Security#ACME clients
.
In
/etc/httpd/conf/httpd.conf
, uncomment the following three lines:
LoadModule ssl_module modules/mod_ssl.so
LoadModule socache_shmcb_module modules/mod_socache_shmcb.so
Include conf/extra/httpd-ssl.conf
If using
Certbot
(
certbot --apache
), the following line needs to be uncommented as well:
LoadModule rewrite_module modules/mod_rewrite.so
After obtaining a key and certificate, make sure the
SSLCertificateFile
and
SSLCertificateKeyFile
lines in
/etc/httpd/conf/extra/httpd-ssl.conf
point to the key and certificate. If a concatenated chain of CA certificates was also generated, add that filename against
SSLCertificateChainFile
.
Finally,
restart
httpd.service
to apply any changes.
Tip
Mozilla has a useful
SSL/TLS article
as well as an
automated tool
to help create a more secure configuration.
Virtual hosts
Note
You will need to add a separate
<VirtualHost *:443>
section for virtual host SSL support.
See
#Managing many virtual hosts
for an example file.
If you want to have more than one host, uncomment the following line in
/etc/httpd/conf/httpd.conf
:
Include conf/extra/httpd-vhosts.conf
In
/etc/httpd/conf/extra/httpd-vhosts.conf
set your virtual hosts. The default file contains an elaborate example that should help you get started.
To test the virtual hosts on your local machine, add the virtual names to your
/etc/hosts
file:
127.0.0.1 domainname1.dom 
127.0.0.1 domainname2.dom
Restart
httpd.service
to apply any changes.
Managing many virtual hosts
Note
Having your virtual servers separated into individual files is mandatory if you plan on using
certbot
to deploy TLS certificates. Having all your virtual servers listed in a single file (as it is by default) will result in certbot failing to deploy the certificates correctly
If you have a huge amount of virtual hosts, you may want to easily disable and enable them. It is recommended to create one configuration file per virtual host and store them all in one folder, eg:
/etc/httpd/conf/vhosts
.
First create the folder:
# mkdir /etc/httpd/conf/vhosts
Then place the single configuration files in it:
# nano /etc/httpd/conf/vhosts/domainname1.dom
# nano /etc/httpd/conf/vhosts/domainname2.dom
...
In the last step,
Include
the single configurations in your
/etc/httpd/conf/httpd.conf
:
#Enabled Vhosts:
Include conf/vhosts/domainname1.dom
Include conf/vhosts/domainname2.dom
You can enable and disable single virtual hosts by commenting or uncommenting them.
A very basic vhost file will look like this:
/etc/httpd/conf/vhosts/domainname1.dom
<VirtualHost *:80>
    ServerAdmin webmaster@domainname1.dom
    DocumentRoot "/home/user/http/domainname1.dom"
    ServerName domainname1.dom
    ServerAlias domainname1.dom
    ErrorLog "/var/log/httpd/domainname1.dom-error_log"
    CustomLog "/var/log/httpd/domainname1.dom-access_log" common

    <Directory "/home/user/http/domainname1.dom">
        Require all granted
    </Directory>
</VirtualHost>

<VirtualHost *:443>
    ServerAdmin webmaster@domainname1.dom
    DocumentRoot "/home/user/http/domainname1.dom"
    ServerName domainname1.dom:443
    ServerAlias domainname1.dom:443
    SSLEngine on
    SSLCertificateFile "/etc/httpd/conf/server.crt"
    SSLCertificateKeyFile "/etc/httpd/conf/server.key"
    ErrorLog "/var/log/httpd/domainname1.dom-error_log"
    CustomLog "/var/log/httpd/domainname1.dom-access_log" common

    <Directory "/home/user/http/domainname1.dom">
        Require all granted
    </Directory>
</VirtualHost>
Extensions
PHP
First
install PHP
, then follow one of the next three subsections below.  Finally, test the installation as described in the final subsection.
Using libphp
This method is probably the easiest, but is also the least scalable: it is suitable for a light request load. It also requires you to change the mpm module, which may cause problems with other extensions (e.g. it is not compatible with
#HTTP/2
).
Install
php-apache
.
Note
If you are using pinned old versions of PHP from AUR, then you should install corresponding pinned version of
php-apache
, i.e.
php56-apache
AUR
for
php56
AUR
.
In
/etc/httpd/conf/httpd.conf
, comment the line:
#LoadModule mpm_event_module modules/mod_mpm_event.so
and uncomment the line:
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
Note
The above is required, because
libphp.so
included with the package does not work with
mod_mpm_event
, but will only work with
mod_mpm_prefork
instead. (
FS#39218
)
Otherwise you will get the following error:
Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe.  You need to recompile PHP.
AH00013: Pre-configuration failed
httpd.service: control process exited, code=exited status=1
As an alternative, you can use
mod_proxy_fcgi
(see
#Using php-fpm and mod_proxy_fcgi
below).
To enable PHP, add these lines to
/etc/httpd/conf/httpd.conf
:
Place this at the end of the
LoadModule
list:
LoadModule php_module modules/libphp.so
AddHandler php-script .php
Place this at the end of the
Include
list:
Include conf/extra/php_module.conf
then
restart
httpd.service
.
Note
For AUR pinned version of PHP, substitute
php_module
,
libphp.so
and
php_module.conf
above accordingly. For example,
php5_module
,
libphp56.so
and
php56-module.conf
for
php56-apache
AUR
.
If you are unsure of the correct substitution, use
pacman -Ql phpXX-apache
to list the correct substitutions of
libphp.so
and
php_module.conf
, then use
nm /usr/lib/httpd/modules/libphpXX.so
to find the correct substitution of
php_module
.
Using apache2-mpm-worker and mod_fcgid
This method provides improved performance and memory usage when serving multiple requests.
Install
mod_fcgid
AUR
and
php-cgi
.
Create the needed directory and symlink it for the PHP wrapper:
# mkdir /srv/http/fcgid-bin
# ln -s /usr/bin/php-cgi /srv/http/fcgid-bin/php-fcgid-wrapper
Create
/etc/httpd/conf/extra/php-fcgid.conf
with the following content:
/etc/httpd/conf/extra/php-fcgid.conf
# Required modules: fcgid_module

<IfModule fcgid_module>
    AddHandler php-fcgid .php
    AddType application/x-httpd-php .php
    Action php-fcgid /fcgid-bin/php-fcgid-wrapper
    ScriptAlias /fcgid-bin/ /srv/http/fcgid-bin/
    SocketPath /var/run/httpd/fcgidsock
    SharememPath /var/run/httpd/fcgid_shm
        # If you don't allow bigger requests many applications may fail (such as WordPress login)
        FcgidMaxRequestLen 536870912
        # Path to php.ini – defaults to /etc/phpX/cgi
        DefaultInitEnv PHPRC=/etc/php/
        # Number of PHP children that will be launched. Leave undefined to let PHP decide.
        #DefaultInitEnv PHP_FCGI_CHILDREN 3
        # Maximum requests before a process is stopped and a new one is launched
        #DefaultInitEnv PHP_FCGI_MAX_REQUESTS 5000
    <Location /fcgid-bin/>
        SetHandler fcgid-script
        Options +ExecCGI
        Require all granted
    </Location>
</IfModule>
Edit
/etc/httpd/conf/httpd.conf
:
Uncomment the loading of the actions module:
LoadModule actions_module modules/mod_actions.so
Load the FCGID module
after
the loading of the unixd module (on which it is dependent) - you may wish to place this within the
<IfModule unixd_module>
block:
LoadModule fcgid_module modules/mod_fcgid.so
Ensure that the inclusion of the MPM configuration is uncommented (it is uncommented in the default installed version of this file):
Include conf/extra/httpd-mpm.conf
Add an inclusion of your new FCGID configuration:
Include conf/extra/php-fcgid.conf
Restart
httpd.service
.
Using php-fpm and mod_proxy_fcgi
This method provides "an alternative PHP FastCGI implementation with some additional features (mostly) useful for heavy-loaded sites"
[1]
.
Note
Unlike the widespread setup with ProxyPass, the proxy configuration with SetHandler respects other Apache directives like DirectoryIndex. This ensures a better compatibility with software designed for libphp, mod_fastcgi and mod_fcgid.
If you still want to try ProxyPass, experiment with a line like this:
ProxyPassMatch ^/(.*\.php(/.*)?)$ unix:/run/php-fpm/php-fpm.sock|fcgi://localhost/srv/http/$1
Install
php-fpm
.
Enable proxy modules:
/etc/httpd/conf/httpd.conf
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_fcgi_module modules/mod_proxy_fcgi.so
Create
/etc/httpd/conf/extra/php-fpm.conf
with the following content:
DirectoryIndex index.php index.html
<FilesMatch \.php$>
    SetHandler "proxy:unix:/run/php-fpm/php-fpm.sock|fcgi://localhost/"
</FilesMatch>
And include it at the bottom of
/etc/httpd/conf/httpd.conf
:
Include conf/extra/php-fpm.conf
Note
The pipe between
sock
and
fcgi
is not allowed to be surrounded by a space!
localhost
can be replaced by any string. More
here
You can configure PHP-FPM in
/etc/php/php-fpm.d/www.conf
, but the default setup should work fine.
Start
and
enable
php-fpm.service
, then
restart
httpd.service
.
Test whether PHP works
To test whether PHP was correctly configured, create a file called
test.php
in your Apache
DocumentRoot
directory (e.g.
/srv/http/
or
~<username>/public_html/
) with the following contents:
<?php phpinfo(); ?>
Then go to
http://localhost/test.php
or http://localhost/~<username>/test.php as appropriate.
HTTP/2
Note
While Apache supports unencrypted HTTP/2 over TCP (
h2c
), common browsers
do not
. Thus for use with the latter,
#TLS
must be enabled first.
If supporting clients do not use HTTP/2 instead of HTTP/1.1 and Mozilla's configuration generator (which already includes the
Protocols
line below) was used to setup
#TLS
, try
Include
ing
httpd-ssl.conf
after
the latter's output.
Ways to test include
curl -sI https://your.website
or use
http indicator
(supports both chromium based browsers and firefox based browsers).
To enable HTTP/2 over TLS support, uncomment the following line in
httpd.conf
:
LoadModule http2_module modules/mod_http2.so
And add the following line:
Protocols h2 http/1.1
To debug, you can set only the module rather than the entire server to
debug
or
info
:
<IfModule http2_module>
    LogLevel http2:info
</IfModule>
For more information – including extra HTTP/2 feature settings – see the
mod_http2
documentation.
Warning
The
http2_module
is incompatible with the
mpm_prefork_module
that old configurations widely use to setup PHP. Consider using
php-fpm
instead.
Troubleshooting
Apache Status and Logs
See the status of the Apache daemon with
systemctl
.
Apache logs can be found in
/var/log/httpd/
Error: PID file /run/httpd/httpd.pid not readable (yet?) after start
Comment out the
unique_id_module
line in
httpd.conf
:
#LoadModule unique_id_module modules/mod_unique_id.so
/run/httpd not being created at boot
If
systemd-tmpfiles --create
as the root user complains about "unsafe path transition", check ownership of your root directory.
ls -la /
chown root:root /
Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe.
If when loading
php_module
the
httpd.service
fails, you may get an error like this in the journal:
Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe.  You need to recompile PHP.
This is because PHP includes support for a module that is not threadsafe, and you are trying to use a threaded MPM. One solution to fix this is to use a non-threaded MPM. Try replacing
mpm_event_module
with
mpm_prefork_module
:
/etc/httpd/conf/httpd.conf
LoadModule mpm_event_module modules/mod_mpm_event.so
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
and
restart
httpd.service
.
Warning
Some other modules, like the
http2_module
, will disable themselves when
mpm_prefork
is active.
AH00534: httpd: Configuration error: No MPM loaded.
You might encounter this error after a recent upgrade. This is only the result of a recent change in
httpd.conf
that you might not have reproduced in your local configuration. To fix it, uncomment the following line:
/etc/httpd/conf/httpd.conf
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
and
restart
httpd.service
.
AH00072: make_sock: could not bind to address
This can be caused by multiple things. Most common issue being that something is already listening on a given port, check via
ss
that this is not happening:
# ss -lnp | grep -e :80 -e :443
If you get any output, stop the given service that's taking up the port or kill the runaway process that is causing the port to be bound, and try again.
Another issue could be that Apache is not starting as root for some reason - try starting it manually and see if you still get the AH0072 error.
# httpd -k start
Finally, you can also have an error with your configuration and you are listening twice on the given port. Following is an example of a bad configuration that will trigger this issue:
Listen 0.0.0.0:80
Listen [::]:80
AH01071: Got error 'Primary script unknown'
This can be caused by
ProtectHome=true
in the php-fpm systemd unit file if you are serving files in
/home
such as in a virtual host environment. You can disable this feature by
editing the php-fpm unit file
and
restarting
php-fpm.service
. Alternatively, move your document root.
Changing the max_execution_time in php.ini has no effect
If you changed the
max_execution_time
in
php.ini
to a value greater than 30 (seconds), you may still get a
503 Service Unavailable
response from Apache after 30 seconds. To solve this, add a
ProxyTimeout
directive to your http configuration right before the
<FilesMatch \.php$>
block:
/etc/httpd/conf/httpd.conf
ProxyTimeout 300
and
restart
httpd.service
.
PHP-FPM: errors are not being logged separately per virtual host
If you have multiple virtual hosts, it may be desirable to have each of them output their error logs to separate files (using the ErrorLog Apache directive). If this is not working for you, confirm that PHP-FPM is configured to log errors to syslog:
/etc/php/php-fpm.conf
error_log = syslog
It is also possible that the pool configuration is overriding it. Ensure the following line is commented out:
/etc/php/php-fpm.d/www.conf
;php_admin_value[error_log] = /var/log/fpm-php.www.log
See also
Apache Official Website
Apache documentation
Apache wiki
Apache documentation - Security Tips
Apache Wiki - Troubleshooting
Apache
on wiki.debian.org