CentOS7.3yum安装MariaDB报错[Errno 256]

在yum安装MariaDB时出现下面这个错误提示，然后着手排查，先检查了/etc/yum.repo.d/下的配置文件，没有错误。

failure: repodata/repomd.xml from mariadb: [Errno 256] No more mirrors to try.
http://yum.mariadb.org/10.3/centos7-amd64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: yum.mariadb.org; 未知的错误"

我这个是云主机，刚想安装LNMP环境。我清理了yum缓存，重新生成缓存，结果也还没解决，还是一样显示上面错误。

然后，我又重新看了错误提示信息，看到下面字样，我就感觉是DNS解析问题了。

Trying other mirror.

查看 /etc/resolv.conf，显示为空，晕了，明明之前配置好了的，难怪yum出问题。然后修改为如下

[root@SERVER1 yum.repos.d]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 223.5.5.5
nameserver 8.8.8.8

清理缓存，重新生成缓存，已正常，问题已经解决

[root@SERVER1 yum.repos.d]# yum clean all
已加载插件：fastestmirror, langpacks
正在清理软件源： base extras mariadb updates
Cleaning up everything
[root@SERVER1 yum.repos.d]# yum makecache
已加载插件：fastestmirror, langpacks
base | 3.6 kB 00:00:00
extras | 3.4 kB 00:00:00
mariadb | 2.9 kB 00:00:00
updates | 3.4 kB 00:00:00
(1/15): base/7/x86_64/group_gz | 166 kB 00:00:00
(2/15): base/7/x86_64/primary_db | 5.9 MB 00:00:00
(3/15): base/7/x86_64/filelists_db | 6.9 MB 00:00:00
(4/15): extras/7/x86_64/prestodelta | 33 kB 00:00:00
(5/15): extras/7/x86_64/primary_db | 125 kB 00:00:00
(6/15): extras/7/x86_64/other_db | 83 kB 00:00:01
(7/15): mariadb/primary_db | 50 kB 00:00:01
(8/15): updates/7/x86_64/filelists_db | 637 kB 00:00:00
(9/15): updates/7/x86_64/prestodelta | 57 kB 00:00:00
(10/15): updates/7/x86_64/primary_db | 1.0 MB 00:00:00
(11/15): updates/7/x86_64/other_db | 55 kB 00:00:00
(12/15): mariadb/other_db | 7.3 kB 00:00:01
(13/15): extras/7/x86_64/filelists_db | 444 kB 00:00:07
(14/15): mariadb/filelists_db | 206 kB 00:00:19
(15/15): base/7/x86_64/other_db | 2.5 MB 00:00:21
Determining fastest mirrors
* base: 100.125.0.40
* extras: 100.125.0.40
* updates: 100.125.0.40
元数据缓存已建立