根据https://github.com/1dot75cm/myrepo中Centos7
RHEL/CentOS 6/7 不包含 dnf 软件包，使用以下命令添加源：
yum-config-manager --add-repo=https://copr.fedoraproject.org/coprs/mosquito/myrepo/repo/epel-$(rpm -E %?rhel)/mosquito-myrepo-epel-$(rpm -E %?rhel).rep
执行这个的时候Could not fetch/save url https://copr.fedoraproject.org/coprs/mosquito/myrepo/repo/epel-7/mosquito-myrepo-epel-7.repo to file /etc/yum.repos.d/mosquito-myrepo-epel-7.repo: [Errno 14] HTTPS Error 404 - Not Found
yum install epel-release
执行后是Package epel-release-7-6.noarch already installed and latest version，说明我曾经已经安装了
yum localinstall http://li.nux.ro/download/nux/dextop/el$(rpm -E %rhel)/x86_64/nux-dextop-release-0-2.el$(rpm -E %rhel).nux.noarch.rpm http://download1.rpmfusion.org/nonfree/el/updates/$(rpm -E %rhel)/x86_64/rpmfusion-nonfree-release-$(rpm -E %rhel)-1.noarch.rpm http://download1.rpmfusion.org/free/el/updates/$(rpm -E %rhel)/x86_64/rpmfusion-free-release-$(rpm -E %rhel)-1.noarch.rpm
执行结果是Cannot open: http://download1.rpmfusion.org/nonfree/el/updates/7/x86_64/rpmfusion-nonfree-release-7-1.noarch.rpm. Skipping.
Cannot open: http://download1.rpmfusion.org/free/el/updates/7/x86_64/rpmfusion-free-release-7-1.noarch.rpm. Skipping.
