解决方案

错误："Could not resolve proxy: https; Unknown error"

说明代理服务器的 /etc/sysconfig/rhn/up2date 配置文件中存在语法问题。

在 /etc/sysconfig/rhn/up2date 中，用户有以下代理条目：

httpProxy=https://www-my-proxy-name:80

当设置了 http 代理时，上面的行中有错字“https”。
此行的格式应如下所示：

httpProxy[comment]=HTTP proxy in host:port format, e.g. squid.example.com:3128

将 https 更改为 http，然后重试 yum 更新。

问题

执行时：

# yum update

出现以下错误：

One of the configured repositories failed (Unknown),
and yum doesn't have enough cached data to continue. At this point the only
safe thing yum can do is fail. There are a few ways to work "fix" this:
1. Contact the upstream for the repository and get them to fix the problem.
2. Reconfigure the baseurl/etc. for the repository, to point to a working
upstream. This is most often useful if you are using a newer
distribution release than is supported by the repository (and the
packages for the previous distribution release still work).
3. Run the command with the repository temporarily disabled
yum --disablerepo= ...
4. Disable the repository permanently, so yum won't use it by default. Yum
will then just ignore the repository until you permanently enable it
again or use --enablerepo for temporary usage:
yum-config-manager --disable 
or
subscription-manager repos --disable=
5. Configure the failing repository to be skipped, if it is unavailable.
Note that yum will try to contact the repo. when it runs most commands,
so will have to try and fail each time (and thus. yum will be much
slower). If it is a very temporary problem though, this is often a nice
compromise:
yum-config-manager --save --setopt=.skip_if_unavailable=true
failed to retrieve repodata/repomd.xml from ol7_x86_64_UEKR4
error was [Errno 14] curl#5 - "Could not resolve proxy: https; Unknown error

“无法解析代理：https；未知错误”