Redhat authentication is launched by Redhat, a well-known manufacturer in the field of server systems. Red Hat certification is divided into three levels: basic RHCT (Red Hat officially cancelled the RHCT exam on January 1, 2011 and changed it to RHCSA), intermediate RHCE, and advanced RHCA. In addition, in 2005, Red Hat introduced a new advanced certification in the field of security: RHCSS。