Linux-云平台主机新增DNS

一、环境说明

• IP是由DHCP获取的，由NetworkManager管理，要永久修改DNS，不能直接编辑 ifcfg-eth0 或 resolv.conf 文件（重启后会被覆盖）

[root@localhost  ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=dhcp
DEVICE=eth0
DHCPV6C=yes
IPV6INIT=yes
IPV6_AUTOCONF=no
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
[root@localhost  ~]# 
[root@localhost  ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
search cluster.local
nameserver 114.114.114.114
nameserver 8.8.8.8
[root@localhost  ~]#

二、解决方法

第一步：找到正确的连接名称
运行以下命令来列出所有 NetworkManager 连接：
nmcli connection show
或者使用简写：

nmcli c s
输出会是一个表格，其中 NAME 列下的就是你需要的连接名称。它很可能是 eth0、Wired connection 1、System eth0 或类似的名称。

# 1. 将当前DNS替换为新的列表（会覆盖原有的DNS）
sudo nmcli connection modify eth0 ipv4.dns "223.5.5.5 1.1.1.1"
# 或 2. 在原有DNS基础上追加新的DNS（保留原有的）
sudo nmcli connection modify eth0 +ipv4.dns "223.5.5.5"
sudo nmcli connection modify eth0 +ipv4.dns "1.1.1.1"

# 确保配置不被DHCP覆盖
sudo nmcli connection modify eth0 ipv4.ignore-auto-dns yes

# 重新激活连接使更改生效
sudo nmcli connection up eth0

三、实操

[root@localhost ~]# nmcli c s
NAME         UUID                                  TYPE      DEVICE 
System eth0  5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03  ethernet  eth0   
[root@localhost ~]# 
[root@localhost ~]# nmcli connection modify "System eth0" +ipv4.dns "110.123.2.5"
[root@localhost ~]# nmcli connection modify "System eth0" +ipv4.dns "110.123.74.253"
[root@localhost ~]# nmcli connection modify "System eth0" ipv4.ignore-auto-dns yes
[root@localhost ~]# nmcli connection up "System eth0"
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)

[root@localhost ~]# 
[root@localhost ~]# ping gng.cqff.hsip.gov.cn
PING gng.cqff.hsip.gov.cn (110.123.34.60) 56(84) bytes of data.
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=1 ttl=52 time=7.57 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=2 ttl=52 time=6.62 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=3 ttl=52 time=6.34 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=4 ttl=52 time=6.47 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=5 ttl=52 time=6.44 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=6 ttl=52 time=6.32 ms
64 bytes from 110.123.34.60 (110.123.34.60): icmp_seq=7 ttl=52 time=6.50 ms

^C
--- ggng.cq.hsip.gov.cn ping statistics ---
15 packets transmitted, 15 received, 0% packet loss, time 14021ms
rtt min/avg/max/mdev = 6.322/6.545/7.567/0.302 ms
[root@localhost ~]# 

四、配置后变化

[root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=dhcp
DEVICE=eth0
DHCPV6C=yes
IPV6INIT=yes
IPV6_AUTOCONF=no
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
PROXY_METHOD=none
BROWSER_ONLY=no
DNS1=110.123.2.5
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
DNS2=110.123.74.253
PEERDNS=no
[root@localhost ~]# 
[root@localhost ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 110.123.2.5
nameserver 110.123.74.253
[root@localhost ~]#