Questions

After installing centos7 (core), the NIC will not be enabled by default. This is a big pit, and the error is reported directly. this is an over optimization . Several developers/operation and maintenance personnel have installed centos7 (core) without SSH to connect to the server

The error is as follows:

Loaded plugins: fastestmirror
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; Unknown error"
http://mirror.centos.org/centos/7/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirror.centos.org; Unknown error"
Trying other mirror.

 One of the configured repositories failed (CentOS-7 - Base),
 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=base ...

     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 base
        or
            subscription-manager repos --disable=base

     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=base.skip_if_unavailable=true

failure: repodata/repomd.xml from base: [Errno 256] No more mirrors to try.
http://mirror.centos.org/centos/7/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirror.centos.org; Unknown error"
[root@localhost ~]#

Solutions

1. After the failure, first, check whether the network is unobstructed

ping www.baidu.com

#google dns
ping 8.8.8.8

There was no response to the above, so I remembered that I had set up a CentOS network card some time ago, and let it start automatically. The order is as follows

vi /etc/sysconfig/network-scripts/ifcfg-ens33

Modify the boot = yes in it

Boot=no (boot up the boot without starting the network card)
#Change to yes

Start network card

ifup ens33

View IP address

ip addr

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:63:c2:ca brd ff:ff:ff:ff:ff:ff
    inet 192.168.152.141/24 brd 192.168.152.255 scope global noprefixroute dynamic ens33
       valid_lft 1319sec preferred_lft 1319sec
    inet6 fe80::fdb9:c978:ff44:dbc5/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

The IP address of the virtual machine is 192.168.152.141

2. Update local cache:

yum makecache

[root@promote ~]# yum makecache
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.cn99.com
 * extras: mirrors.njupt.edu.cn
 * updates: mirrors.cn99.com
base                                                                                                                                     | 3.6 kB  00:00:00
extras                                                                                                                                   | 3.4 kB  00:00:00
updates                                                                                                                                  | 3.4 kB  00:00:00
(1/8): extras/7/x86_64/other_db                                                                                                          | 127 kB  00:00:00
(2/8): extras/7/x86_64/filelists_db                                                                                                      | 246 kB  00:00:00
(3/8): updates/7/x86_64/prestodelta                                                                                                      | 797 kB  00:00:00
(4/8): updates/7/x86_64/other_db                                                                                                         | 641 kB  00:00:00
(5/8): base/7/x86_64/other_db                                                                                                            | 2.6 MB  00:00:01
(6/8): base/7/x86_64/filelists_db                                                                                                        | 7.1 MB  00:00:02
(7/8): updates/7/x86_64/filelists_db                                                                                                     | 4.4 MB  00:00:03
extras/7/x86_64/prestodelta    FAILED
http://mirrors.njupt.edu.cn/centos/7.6.1810/extras/x86_64/repodata/5bfd3d5f07606011226e556e87d978ca1dfe51a63e18d793182900d5bbc702b5-prestodelta.xml.gz: [Errno 14] HTTP Error 302 - Found
Trying other mirror.
(8/8): extras/7/x86_64/prestodelta                                                                                                       |  65 kB  00:00:00
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