How To Set Up Apache Virtual Hosts on CentOS 7 | DigitalOcean https://www.digitalocean.com/community/tutorials/how-to-set-up-apache-virtual-hosts-on-centos-7
How to troubleshoot DNS with dig and nslookup https://www.a2hosting.com/kb/getting-started-guide/internet-and-networking/troubleshooting-dns-with-dig-and-nslookup
Compare text files with TextWrangler – Uros Baric http://urosbaric.com/compare-files-with-textwrangler