I Use Centos5 as my Linux system operation. Default mono-core installed in centos is mono-core-1.2.4-2.el5.centos. This version is to old and I want to install or upgrade mono. This is a method how to install or upgrade mono in Centos5. Create a new repo config file. vim /etc/yum.repos.d/mono.repo and add the following text : [Mono]