"Resolving timed out after 30553 milliseconds" error solution appears in yum execution under linux

One, there is a problem

An error message appears:

[root@xsnq ~] yum -y install wget
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=
x86_64&repo=os&infra=genclo error was 12: Timeout on http://mirrorlist.cento
s.org/?release=7&arch=x86_64&repo=os&infra=genclo:
 (28, 'Resolving timed out after 30553 milliseconds')

 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=<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

2. Reasons

The error message is that the resolution timed out , indicating the reason for the network connection.

The reasons for the connection failure may include:

1. DNS resolution failed
2. Bad signal
3. Network outage, etc.

Three, the solution

1. Modify resolv.conf

[root@localhost ~] vim /etc/resolv.conf

Add a nameserver:

It is best not to modify the nameserver, you can add the nameserver you want to use first in front of the other nameservers as the primary DNS.

nameserver 8.8.8.8                              更适合国外以及访问国外网站的用户使用
或者
nameserver 114.114.114.114                      更适合国内用户

So far the problem has been resolved (the modification will take effect immediately without any additional processing; if it is the modified ifcfg-eth file, the network card needs to be restarted to take effect)

Note: The reading is carried out according to the order of the nameserver in this file, and the following nameserver will be queried when the first nameserver does not respond

2. View dns

[root@localhost ~] cat /etc/resolv.conf

Expand

National DNS query: click here

References: IP.cn query network; https://ip.cn/dns.html

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