Installing and Configuring FastCGI and PHP-FPM Using Debian 11 and PHP 7.4

mod_fcgid is an Apache module that uses the FastCGI protocol to provide an interface between Apache and Common Gateway Interface (CGI) programs. CGI helps a web server handle dynamic content generation and processing for scripting languages like PHP. This dynamic functionality is commonly used when running content management systems like WordPress on a LAMP stack.

This guide will show you how to install mod_fcgid and PHP-FPM on Debian 11. It also provides a basic configuration that uses socket based connections, instead of TCP. These steps will enable you to run PHP through mod_fcgid. Running PHP through mod_fcgid helps to reduce the amount of system resources used by forcing the web server to act as a proxy and only pass files ending with the .php file extension to PHP-FPM. Additionally, using PHP-FPM allows each virtual host to be configured to run PHP code as individual users.

This guide assumes that you are familiar and comfortable with setting up a LAMP stack on Debian 11. If you are new to Linux server administration, you may be interested in reading our Linux System Administration Basics guide.

Before You Begin

1. Complete the steps in the How to Install a LAMP Stack on Debian 11 guide. After completing the LAMP stack guide, you should have an Apache virtual hosts configuration for your own website. This guide will refer to the site as example.com.

   Note

   This guide’s examples use PHP version 7.4. When running commands related to PHP, ensure you replace any version numbers with your own system’s PHP version.

Install mod_fcgid and PHP-FPM

In this section, you will install the mod_fcgid and PHP-FPM modules on your Debian 10 Linode.

1. Update your system’s Apt repositories.

   sudo apt-get update && sudo apt-get upgrade --show-upgraded

2. Install mod_fcgid, PHP-FPM, and htop. You will need the htop command line utility in a later section of this guide.

   sudo apt-get install libapache2-mod-fcgid php-fpm htop

3. To load the mod_proxy and mod_proxy_fcgi modules, edit your main Apache configuration, and add the lines included in the example. Both modules are included by default in your Apache installation, but they must be explicitly loaded in order to use them. You will need these modules to proxy requests through mod_fcgid to your socket.

   File: /etc/apache2/apache2.conf

   1 2	LoadModule proxy_module /usr/lib/apache2/modules/mod_proxy.so LoadModule proxy_fcgi_module /usr/lib/apache2/modules/mod_proxy_fcgi.so

4. Verify that the configuration is correct:

   sudo apache2ctl configtest

5. Restart the Apache web server:

   sudo systemctl restart apache2

Configure Apache with PHP-FPM

You will now configure Apache to pass all requests for files with the .php extension to the PHP wrapper through FastCGI.

1. Configure PHP-FPM to use UNIX sockets instead of TCP. In this command, you will use grep to determine if the sockets are already being used. This command will search your php-fpm installation’s default pool configuration file for the setting:

   sudo grep -E '^\s*listen\s*=\s*[a-zA-Z/]+' /etc/php/7.4/fpm/pool.d/www.conf

   You should see the example output:

   listen = /run/php/php7.4-fpm.sock

   If you see the above output, skip to step 6, otherwise continue to the next step to manually configure your UNIX steps.

2. If no output is returned, you will need to edit your PHP pool configuration file by adding a listen setting with the address on which to accept FastCGI requests. Add the line in the example file.

   File: /etc/php/7.4/fpm/pool.d/www.conf

   1	listen = /var/run/php/php7.4-fpm.sock

3. If the listen.allowed_cclients = 127.0.0.1 is not already uncommented, do so now.

   File: /etc/php/7.4/fpm/pool.d/www.conf

   1	listen.allowed_clients = 127.0.0.1

4. Restart the php-fpm daemon for these changes to take effect.

   sudo systemctl restart php7.4-fpm

5. Update your default Apache configuration file with the following basic settings for mod_fcgid. You may consider changing these settings based on your own needs.

   File: /etc/apache2/apache2.conf

   1 2 3 4 5

   AddHandler fcgid-script .fcgi .php .fpl FcgidConnectTimeout 20 FcgidMaxRequestLen 268435456 FcgidMaxProcessesPerClass 10 FcgidIOTimeout 300

6. Check for configuration errors.

   sudo apache2ctl configtest

7. Edit your FastCGI module’s configuration file to add the settings in the example file. Some of the example settings may already be included in your configuration. Add the missing settings.

   File: /etc/apache2/mods-available/fcgid.conf

   1 2 3 4 5 6 7 8 9

   <IfModule mod_fcgid.c> FcgidConnectTimeout 20 AddType application/x-httpd-php .php AddHandler application/x-httpd-php .php Alias /php7-fcgi /usr/lib/cgi-bin/php7-fcgi <IfModule mod_mime.c> AddHandler fcgid-script .fcgi </IfModule> </IfModule>

8. Check for configuration errors.

   sudo apache2ctl configtest

9. If you received Syntax OK for steps 6 and 8, restart the Apache service.

   sudo systemctl restart apache2

10. Check if PHP is working by creating and accessing a page with phpinfo() displayed. The following command will create a new file info.php in /var/www/example.com/html/public_html/info.php. Replace example.com with your own domain’s root directory name.

    sudo echo "<?php phpinfo(); ?>" > /var/www/html/example.com/public_html/info.php

    Navigate to www.example.com/info.php to view your system’s information.

Configuring PHP Pools

PHP-FPM brings in the concept of pools. With pools, PHP-FPM can create and manage a pool of PHP processes to run PHP files from a site’s root directory. Each pool that is run by PHP-FPM can be run with separate user and group ID’s. Pools are a great way to provide more security when you are running multiple sites on one server. Running your site’s PHP scripts using dedicated user and group IDs means that no one user can execute scripts on all sites running on your Linode. In this section you will create a pool for the domain example.com which is owned by the user www-data.

1. Create a copy of your original pool file to use as the foundation for your example.com pool configuration.

   sudo cp /etc/php/7.4/fpm/pool.d/www.conf /etc/php/7.4/fpm/pool.d/example.com.conf

2. Edit the file to change the socket name, user and group, and socket listen address. Ensure that the listen address is different from the listen address that you set in the main PHP pool configuration file. You can append the name of your site as part of the file name, for example: listen = /var/run/php/php7.4-fpm_example.com.sock. Also, ensure that you comment out or replace any existing user and group and add your own user and group settings as shown in the example.

   File: /etc/php/7.4/fpm/pool.d/example.com.conf

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

   ; Start a new pool named 'www'. ; the variable $pool can be used in any directive and will be replaced by the ; pool name ('www' here) [example.com] ... ; Unix user/group of processes ; Note: The user is mandatory. If the group is not set, the default user's group ; will be used. user = www-data group = www-data ... listen = /var/run/php/php7.4-fpm_example.com.sock

3. Restart the php7.4-fpm process for the new pool to be created.

   sudo systemctl restart php7.4-fpm

4. Edit the virtual host file of example.com to use your new PHP-FPM pool. What you need to add or edit may differ depending on the current configuration of your virtual hosts file. The <IfModuel mod_fcgid.c> directive and its contents is what you should add to your file. Ensure you replace any instance of example.com with your own domain name.

   File: /etc/apache2/sites-available/example.com.conf

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

   <Directory /var/www/html/example.com/public_html> Require all granted </Directory> <VirtualHost *:80> ServerAdmin webmaster@example.com ServerName example.com ServerAlias www.example.com DocumentRoot /var/www/html/example.com/public_html ErrorLog /var/www/html/example.com/logs/error.log CustomLog /var/www/html/example.com/logs/access.log combined DirectoryIndex index.php <IfModule mod_fcgid.c> Options +ExecCGI FcgidConnectTimeout 20 AddType application/x-httpd-php .php AddHandler application/x-httpd-php .php Alias /php7-fcgi /usr/lib/cgi-bin/php7-fcgi ProxyPassMatch " ^/(.*\.php(/.*)?)$" "unix:/run/php/php7.4-fpm_example.com.sock|fcgi://localhost/var/www/html/example.com/public_html/" </IfModule> </VirtualHost>

5. Check the configuration file for errors.

   sudo apache2ctl configtest
   Note

   If Apache continues to use apache handler, then Pass use apache: a2enconf php7.4-fpm and a2dismod php7.4.

6. If there were no errors, restart Apache.

   sudo systemctl restart apache2

7. Use the command line tool top to verify that PHP-FPM is running the example.com pool as the www-data user and group. Replace `www-data with the user that you defined in your pool configuration file.

   top -c -u www-data

   Your output should display www-data as the user corresponding to the command that started the listed process php-fpm: pool example.com.

   PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
      1978 www-data  20   0    3492    164      0 S   0.0   0.0   0:00.10 /usr/bin/htcacheclean -d 120 -p /var/cache/apache2/mod_cache_disk +
     16234 www-data  20   0  207256  10348   4100 S   0.0   0.3   0:00.00 php-fpm: pool www
     16235 www-data  20   0  207256  10348   4100 S   0.0   0.3   0:00.00 php-fpm: pool www
     16255 www-data  20   0   52328   5748   3228 S   0.0   0.1   0:00.00 /usr/sbin/apache2 -k start