yum update 出错

: mirrors.163.com; Unknown error"
Trying other mirror.
yum-utils-1.1.31-52.el7.noarch FAILED
http://ap.stykers.moe/centos/7.7.1908/os/x86_64/Packages/yum-utils-1.1.31-52.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: ap.stykers.moe; Unknown error"
Trying other mirror.
lvm2-2.02.185-2.el7.x86_64.rpm FAILED
http://mirrors.neusoft.edu.cn/centos/7.7.1908/os/x86_64/Packages/lvm2-2.02.185-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.neusoft.edu.cn; Unknown error"
Trying other mirror.
lvm2-libs-2.02.185-2.el7.x86_6 FAILED
http://ftp.sjtu.edu.cn/centos/7.7.1908/os/x86_64/Packages/lvm2-libs-2.02.185-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: ftp.sjtu.edu.cn; Unknown error"
Trying other mirror.
python-chardet-2.2.1-3.el7.noa FAILED
http://ftp.sjtu.edu.cn/centos/7.7.1908/os/x86_64/Packages/python-chardet-2.2.1-3.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: ftp.sjtu.edu.cn; Unknown error"
Trying other mirror.
libxml2-python-2.9.1-6.el7_2.3 FAILED
http://centos.ustc.edu.cn/centos/7.7.1908/os/x86_64/Packages/libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: centos.ustc.edu.cn; Unknown error"
Trying other mirror.
python-kitchen-1.1.1-5.el7.noa FAILED
http://mirrors.aliyun.com/centos/7.7.1908/os/x86_64/Packages/python-kitchen-1.1.1-5.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
Trying other mirror.
device-mapper-1.02.158-2.el7.x FAILED
http://mirrors.neusoft.edu.cn/centos/7.7.1908/os/x86_64/Packages/device-mapper-1.02.158-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.neusoft.edu.cn; Unknown error"
Trying other mirror.
device-mapper-persistent-data- FAILED
http://mirrors.huaweicloud.com/centos/7.7.1908/os/x86_64/Packages/device-mapper-persistent-data-0.8.5-1.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.huaweicloud.com; Unknown error"
Trying other mirror.
device-mapper-event-libs-1.02. FAILED
http://mirrors.aliyun.com/centos/7.7.1908/os/x86_64/Packages/device-mapper-event-libs-1.02.158-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.aliyun.com; Unknown error"
Trying other mirror.
device-mapper-event-1.02.158-2 FAILED
http://mirrors.tuna.tsinghua.edu.cn/centos/7.7.1908/os/x86_64/Packages/device-mapper-event-1.02.158-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.tuna.tsinghua.edu.cn; Unknown error"
Trying other mirror.
device-mapper-libs-1.02.158-2. FAILED
http://mirrors.zju.edu.cn/centos/7.7.1908/os/x86_64/Packages/device-mapper-libs-1.02.158-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.zju.edu.cn; Unknown error"
Trying other mirror.
yum-utils-1.1.31-52.el7.noarch FAILED
http://mirror.jdcloud.com/centos/7.7.1908/os/x86_64/Packages/yum-utils-1.1.31-52.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: mirror.jdcloud.com; Unknown error"
Trying other mirror.
lvm2-2.02.185-2.el7.x86_64.rpm FAILED
http://mirrors.huaweicloud.com/centos/7.7.1908/os/x86_64/Packages/lvm2-2.02.185-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.huaweicloud.com; Unknown error"
Trying other mirror.
python-chardet-2.2.1-3.el7.noa FAILED
http://ap.stykers.moe/centos/7.7.1908/os/x86_64/Packages/python-chardet-2.2.1-3.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: ap.stykers.moe; Unknown error"
Trying other mirror.
lvm2-libs-2.02.185-2.el7.x86_6 FAILED
http://mirror.jdcloud.com/centos/7.7.1908/os/x86_64/Packages/lvm2-libs-2.02.185-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: mirror.jdcloud.com; Unknown error"
Trying other mirror.
python-kitchen-1.1.1-5.el7.noa FAILED
http://mirrors.neusoft.edu.cn/centos/7.7.1908/os/x86_64/Packages/python-kitchen-1.1.1-5.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.neusoft.edu.cn; Unknown error"
Trying other mirror.
device-mapper-1.02.158-2.el7.x FAILED
http://ap.stykers.moe/centos/7.7.1908/os/x86_64/Packages/device-mapper-1.02.158-2.el7.x86_64.rpm: [Errno 14] curl#6 - "Could not resolve host: ap.stykers.moe; Unknown error"
Trying other mirror.
yum-utils-1.1.31-52.el7.noarch FAILED
http://mirrors.zju.edu.cn/centos/7.7.1908/os/x86_64/Packages/yum-utils-1.1.31-52.el7.noarch.rpm: [Errno 14] curl#6 - "Could not resolve host: mirrors.zju.edu.cn; Unknown error"
Trying other mirror.

Error downloading packages:
  7:lvm2-libs-2.02.185-2.el7.x86_64: [Errno 256] No more mirrors to try.
  libxml2-python-2.9.1-6.el7_2.3.x86_64: [Errno 256] No more mirrors to try.
  device-mapper-persistent-data-0.8.5-1.el7.x86_64: [Errno 256] No more mirrors to try.
  python-kitchen-1.1.1-5.el7.noarch: [Errno 256] No more mirrors to try.
  yum-utils-1.1.31-52.el7.noarch: [Errno 256] No more mirrors to try.
  7:device-mapper-libs-1.02.158-2.el7.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-event-libs-1.02.158-2.el7.x86_64: [Errno 256] No more mirrors to try.
  7:device-mapper-1.02.158-2.el7.x86_64: [Errno 256] No more mirrors to try.
  7:lvm2-2.02.185-2.el7.x86_64: [Errno 256] No more mirrors to try.
  python-chardet-2.2.1-3.el7.noarch: [Errno 256] No more mirrors to try.

然后 ping 一下百度， 显示无法识别

[[email protected] etc]# ping www.baidu.com
ping: www.baidu.com: Name or service not known

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

下的BOOTPROTO 为 dhcp

重启网络 systemctl restart network

ping 百度 成功

再 yum update 成功

原文地址：https://www.cnblogs.com/Jomini/p/12026306.html