How to Install and Configure Memcached on CentOS 7

Memcached is a free, open-source, high-performance and distributed memory caching system used to speed up dynamic websites by caching data in RAM. Memcached also provides a library for different programming languages including, PHP, Perl, Ruby, and Python. Memcached is the only caching system available for free and used by many organizations including, YouTube, Facebook, Twitter, Reddit, Drupal and Zynga.

In this tutorial, we will show you how to install and configure Memcached on CentOS 7 server.

Requirements

• A cloud server running CentOS 7 with PHP and Apache installed.
• A root password configured on your server.

Getting Started

By default, SELinux is enabled in CentOS 8 server. So you will need to disable it first.

You can do this by editing /etc/selinux/config file:

# nano /etc/selinux/config

Change the following line:

SELINUX=disabled

Save and close the file. Then, restart your server to apply the changes.

Install Memcached

By default, Memcached is available in the CentOS 7 default repository. You can install it by just running the following command:

# yum install memcached -y

Once Memcached is installed, start the Memcached service and enable it to start after system reboot with the following command:

# systemctl start memcached
# systemctl enable memcached

You can now check the status of Memcached with the following command:

# systemctl status memcached

You should see the following output:

  ● memcached.service - Memcached
  Loaded: loaded (/usr/lib/systemd/system/memcached.service; disabled; vendor preset:
  disabled)
  Active: active (running) since Sat 2019-11-09 00:09:32 EST; 4s ago
  Main PID: 3450 (memcached)
  CGroup: /system.slice/memcached.service
  └─3450 /usr/bin/memcached -u memcached -p 11211 -m 64 -c 1024

  Nov 09 00:09:32 localhost.localdomain systemd[1]: Started Memcached.

Configure Memcached

By default, Memcached is configured to listen on port 11211 on all interface. So it is recommended to configure Memcached to listen on the local (127.0.0.1) interface only. This will protect your server from denial of service attacks. You can do it by editing the Memcached default configuration file /etc/sysconfig/memcached:

# nano /etc/sysconfig/memcached

Make the following changes:

  PORT="11211"
  USER="memcached"
  MAXCONN="1024"
  CACHESIZE="64"
  OPTIONS="-l 127.0.0.1"

Save and close the file when you are finished. Then, restart the Memcached service to apply the configuration changes:

 # systemctl restart memcached

Now, you can check the Memcached listening interface with the following command:

 # netstat -tulpn | grep :11211

You should see the following output:

tcp   0      0 127.0.0.1:11211      0.0.0.0:*        LISTEN      3598/memcached
udp   0      0 127.0.0.1:11211      0.0.0.0:*                    3598/memcached

You can also check the status of the Memcached server with the following command:

 # memcached-tool 127.0.0.1 stats

Install Memcached PHP Extension

If you want to use Memcached as a caching database for PHP-based applications. Then, you will need to install Memcached PHP extension on your server. You can install it with the following command:

 # yum install php-pecl-memcache -y

Once installed, restart the Apache web service to apply the changes:

 # systemctl restart httpd

Test Memcached PHP Extension

To test Memcached PHP extension, create an info.php file in Apache web root directory:

# nano /var/www/html/info.php

Add the following lines:

<?php
 phpinfo();
?>

Save and close the file when you are finished.

Next, create an Apache virtual host file with the following command:

 # nano /etc/httpd/conf.d/memcache.conf

Add the following lines:

ServerAdmin admin@yourdomain.com
DocumentRoot /var/www/html/
ServerName yourdomain.com
DirectoryIndex info.php

Options FollowSymLinks
AllowOverride All

ErrorLog /var/log/httpd/error_log
CustomLog /var/log/httpd/access_log common

Save and close the file when you are finished. Then, restart the Apache service to apply the changes:

 # systemctl restart httpd

Now, open your web browser and type the URL http://yourdomain.com. You should see the following screen:

The above page indicates that Memcached is installed with PHP support.

Conclusion

In the above tutorial, you learned how to install Memcached on CentOS 7 server. You can now easily cache your PHP-based application with Memcached.