CentOS 7 is a free Linux distribution based on Red Hat Enterprise Linux (RHEL) 7. It was announced in 2014 with long-term 10-year support and significant improvements compared to the previous version - better system management, improved user interface, improved safety and many more.
The CentOS 7 distribution has a new system settings management system called "systemd" that replaces the old "init" system and provides improved system security support, including SELinux (Security-Enhanced Linux) and many other security tools.