Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 - 1000x, depending on your architecture. In this documentation, I will show how to install Varnish 4 on CentOS 6.

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For first installation install Varnish repository

sudo rpm --nosignature -i https://repo.varnish-cache.org/redhat/varnish-4.0.el6.rpm

Then install Varnish

sudo yum install varnish

Start Varnish service and configure it to start at boot

sudo service varnish start
sudo chkconfig varnish on

Reference: https://www.varnish-cache.org/installation/redhat