CentOs 7 YUM更新不起作用

我正在尝试执行操作，yum update并且所有镜像都失败并显示404。我将URL放入浏览器，并且错误是正确的，该URL不存在。YUM正在寻找镜子上不存在的包装。请参阅以下错误消息：

https://mirrors.lug.mtu.edu/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTPS Error 404 - Not Found
Trying other mirror.
http://mirror.oss.ou.edu/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
https://mirror.csclub.uwaterloo.ca/fedora/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTPS Error 404 - Not Found
Trying other mirror.
http://mirror.sfo12.us.leaseweb.net/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
http://mirror.math.princeton.edu/pub/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
http://kdeforge2.unl.edu/mirrors/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
https://muug.ca/mirror/fedora-epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTPS Error 404 - Not Found
Trying other mirror.
http://fedora.westmancom.com/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTP Error 404 - Not Found
Trying other mirror.
https://ca.mirror.babylon.network/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTPS Error 404 - Not Found
Trying other mirror.
https://mirror.chpc.utah.edu/pub/epel/7/x86_64/repodata/13b91b1efe2a1db71aa132d76383fdb5311887958a910548546d58a5856e2c5d-primary.sqlite.xz: [Errno 14] HTTPS Error 404 - Not Found
Trying other mirror.

我已经尝试运行yum clean all 该命令成功完成，但是它没有任何改变。我也尝试了以下方法：

rm -f /var/lib//rpm/__db*
rpm --rebuilddb

那也没有改变任何东西。

编辑/etc/yum.conf文件并添加

http_caching=packages

以下内容也适用：

yum clean all
yum makecache
yum update

我有一个很久没有更新的VM，yum makecache fast并且yum update为我工作了。

运行以下命令，yum安装成功完成：

yum clean all