How to reveal Real IP Cloudflare using Ubuntu 18.04

Mod_cloudflare has a few software dependencies that need to be installed first:

# yum install libtool httpd-devel

Next, you should download the mod_cloudflare source to your server:

# wget https://raw.githubusercontent.com/cloudflare/mod_cloudflare/master/mod_cloudflare.c

Finally, install the module. Depending on your system, the command to run might be apxs or apxs2. So, run one of the below two commands. If you get a ‘Command not found’ when running one, try the other:

# apxs -a -i -c mod_cloudflare.c
# apxs2 -a -i -c mod_cloudflare.c

Source : https://www.cloudflare.com/technical-resources/#mod_cloudflare