[centos upgrade] Proper upgrade from CentOS 6 to CentOS 7

quote

redhat-upgrade-tool --force --network 7.0 --instrepo http://centos.communilink.net/7.3.1611/os/x86_64/

Use --force option to force upgrade

Reference : http://blog.hlogc.com/20160313/upgrade-from-centos-6-to-centos-7/


centos7 download address: http://mirrors.gigenet.com/ centos/7/isos/x86_64/
http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-Everything-1611.iso