Change the --releasever= number if you want to upgrade to a different system release. Most people will want to upgrade to the latest stable release, which is 25, but if you're running Fedora 23, you might want to upgrade just to Fedora 24. You can also use 26 for upgrading to Branched or rawhide for upgrading to Rawhide (warning: those are not stable releases).
使用这个命令了吗?DNF system upgrade
官方wiki
其中表明: