If for whatever reason, you are stuck with the now EOL version of the CentOS operating system, you can no longer run yum upgrade successfully. Running yum upgrade in CentOS 6 will yield the following results:Setting up Upgrade ProcessYumRepo Error: All mirror URLs are not using ftp, http[s] or file.Eg. Invalid release/repo/arch combination/removing mirrorlist with no valid mirrors: /var/cache/yum/x86_64/6/base/mirrorlist.txtError: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please...