How to Install Redis Cache Server on CentOS 7/6

Redis is an in-memory data structure store, used as a database server, cache, and message broker. It also provides a PHP module for communication between PHP script with the Redis server. Redis is written in C programming language.

This tutorial will help you with the installation of the Redis server along with PHP Redis PHP extensions on a CentOS 7/6 server.

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Step 1 – Prerequisites

First of all, log in to your server using shell access with the root account.

ssh root@remote

Redis packages are not available under default yum repositories. You need to enable EPEL yum repository on your server first. Execute below command to enable:

### CentOS/RHEL 7 
yum install epel-release

### CentOS/RHEL 6 
rpm -Uvh http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

Step 2 – Install Redis Server

Now, You can use the yum package manager to install the Redis server on a VPS. Execute command to install Redis on your systems:

yum install redis

After successfully installation start Redis service and enable auto-start on system reboot.

### CentOS/RHEL 7 
systemctl enable redis
systemctl start redis

### CentOS/RHEL 6 
chkconfig redis on
service redis restart

Redis server is up and running on your system.

Step 3 – Install Redis PHP extension

We assume you already have PHP installed on your system. You must have PHP pear package installed on your system.

yum install php-pear php-devel

Now, execute commands to enable Redis PHP extension on your CentOS server.

pecl install igbinary igbinary-devel redis

After that execute a command to verify Redis PHP extension is enabled:

php -m | grep redis

Redis server has been installed on your system along with the PHP extension.

Step 4 – Configure Redis as a Cache Server

Redis can be started without a configuration file using a built-in default configuration. But to make any extra parameter changes you can use its configuration file that is: /etc/redis/redis.conf. Edit the Redis configuration file in a text editor to make changes

vim /etc/redis/redis.conf

Update the following values in the Redis configuration file according to your requirement. You can increase the max memory limit as per available on your server.

maxmemory 256mb
maxmemory-policy allkeys-lru

The above configuration tells Redis to remove any key using the LRU algorithm when the max memory of 256mb is reached. Save the configuration file and restart the Redis service:

Step 5 – Test Connection to Redis Server

Use redis-cli tool to verify the connection between the Redis server and redis-cli.

redis-cli

127.0.0.1:6379> ping
PONG
127.0.0.1:6379>