1.yum update
?
2.yum install fedup
3.?fedup --network 21 --product=[workstation][server][cloud](如fedup --network 21 --product=server)
4.重启，选择“System Upgrade(fedup)”启动项
5.升级成功。
fedora21之fedora20升级到fedora21
原文：http://wiselyman.iteye.com/blog/2169166
