业务需求安装一个免费的ssl毫不犹豫想到了Let's Encrypt，于是yum 安装，但是这台机器上面遇到了怪事，没有可用的安装包，于是换了几次阿里，163，sohu源，换过cdn最终还是没能成功，照旧No package certbot available，呃呵，卸载重装epel-release.noarch，折腾了好久没解决。@H_502_3@

后来找到原因尴尬了这台服务器同事以前安装插件时候把CentOS-Epel.repo 设置成enabled=0以后就没改回来。@H_502_3@

yum update 不更新内核只更软件以下两个办法:@H_502_3@

1.@H_502_3@

yum –exclude=kernel* update@H_502_3@

2.@H_502_3@

vim /etc/yum.conf@H_502_3@

[main]@H_502_3@

最后面添加@H_502_3@

exclude=kernel*@H_502_3@

exclude=centos-release*@H_502_3@

@H_502_3@

更新repo源：@H_502_3@

1.cd /etc/yum.repos.d/@H_502_3@

2.mv CentOS-Base.repo CentOS-Base.repo.bak@H_502_3@

3.@H_502_3@

curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo@H_502_3@

或者@H_502_3@

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo@H_502_3@

@H_502_3@

mv Centos-7.repo CentOS-Base.repo@H_502_3@

yum clean all
@H_502_3@

yum makecache@H_502_3@