希望能尽快解决，不然工具用不了，买的课不就白买了

Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was

14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"

 One of the configured repositories failed (未知),

 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=<repoid> ...

     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 <repoid>

        or

            subscription-manager repos --disable=<repoid>

     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 be much

        slower). If it is a very temporary problem though, this is often a nice

        compromise:

            yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true

Cannot find a valid baseurl for repo: base/7/x86_64

按照视频输入systemctl start ntpd， 输出结果为 failed to start ntpd， unit is masked。 按照网上教程输入 systemctl unmask ntpd.service 无效。

ntpd status 为 masked，怎么解决

老师，我finalshell连接不上虚拟机，我虚拟机可以ping百度，主机可以ping虚拟机，虚拟机可以ping主机，相关服务是自动启用的，网络配置也没有问题，主机跟虚拟机的防火墙也关了但是还是会出现

java.net.ConnectException: Connection refused: connect

这个错误提示

在正式使用的时候，服务器的节点很多加上节点之间也有访问～不会也是每次都手动配置吧。在实际的项目里，增加节点都是怎么操作的？

#!/bin/awk -f  
{
     split($5,date,"-")
     if (date[2]=="1"){
        map_name_money[$1]+=$5
        if ($2=="0"){
            map_name_role[$1]="manager"
        }else{
            map_name_role[$1]="worker"
        }
    }
}
END{
   for (name in map_name_money){
       print name "\t" map_name_role[name] "\t" map_name_money[name]
   }
}

老师，我实在找不出哪里有错，执行不出来，就会出现下面的情况

但是复制教程代码就没有可以执行出来。

window10每次打开虚拟机都蓝屏咋办

老师，从你这下载的软件出现这个问题需要怎么解决？

老师可不可以理解为软连接是快捷方式

硬链接就是复制了一个文档

这个排序没看明白 听的不是太懂

ping  百度后  出现这种情况后是前边操作有问题吗

老师，什么情况下该使用软连接？什么情况下该使用硬链接？  谢谢