Detailed explanation of Cent0S 6.7 operations under the /etc/resolv.conf file

This article mainly introduces the solution to the problem of Cent0S 6.7 that modifying the DNS address directly under the /etc/resolv.conf file and restarting does not take effect. Friends in need can refer to

Setting the IP address under CentOS 6.7/Linux

1: Temporary modification:

1.1: Modify IP address # ifconfig eth0 192.168.2.104

1.2: Modify gateway Address# route add default gw 192.168.2.1 dev eth0

1.3: Modify DNS # echo "nameserver 192.168.2.1" >> /etc/resolv.conf // Consistent with the host’s DNS server

You can access the Internet at this time. The IP address for accessing the Internet is 192.168.2.104, and the gateway address is 192.168.2.1. However, this setting is temporary. Once the network card is restarted or the server is restarted, all operations except 1.3 will be restored. This method is only suitable for temporary IP modification. If you want to permanently modify the network card configuration file, you need to modify the corresponding file.

2: Permanent modification:

2.1: Modify IP address

Modify /etc/sysconfig/network-scripts /ifcfg-eth0 file, if there are multiple network cards, modify the corresponding network card

# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0               #网卡对应的设备别名
BOOTPROTO=static          #网卡获得ip地址的方式（默认为dhcp，表示自动获取）
HWADDR=08:00:27:F9:5B:B9  #网卡MAC地址（物理地址）
IPADDR=192.168.2.104       #IP地址
NETMASK=255.255.255.0     #子网掩码 
ONBOOT=yes              #系统启动时是否激活此设备

2.2: Modify the gateway address

Modify /etc/sysconfig/ network file

# vi /etc/sysconfig/network
NETWORKING=yes        #表示系统是否使用网络，no表示不能使用网络
HOSTNAME=doiido        #设置本机的主机名，要和/etc/hosts中设置的主机名相同
GATEWAY=192.168.100.1   #设置网关的IP地址

At this time, the IP address can be pinged, but the domain name cannot be pinged, so the DNS needs to be modified

2.3: Modify DNS

Modify the /etc/resolv.conf file

# vi /etc/resolv.conf
nameserver 192.168.2.1     #与主机DNS服务器保持一致
nameserver 114.144.114.114   #国内域名服务器

2.4: Restart the network card

# service network restart

is shutting down Interface eth0: [OK]

Close the loopback interface: [OK]

Pop up the loopback interface: [OK]

Pop up the interface eth0: [OK]

At this time, can the system access the Internet normally? It is possible under normal circumstances, but when I tried this in centos 6.7, I found that I could still only ping the IP address and could not access the domain name. I searched online

It turns out that directly modifying /etc/resolv.conf under Centos6.7 does not work. The dns settings must be added to /etc/sysconfig/network-scripts/ifcfg-eth0 at the end. Otherwise, after restarting, the dns-related information in the eth0 settings must be used to restore /etc/resolv.conf to its original state.

Open /etc/sysconfig/network-scripts/ifcfg-eth0 and add the DNS configuration in it

##

[root@localhost /]# vi /etc/sysconfig/network-scripts/ifcfg-eth0 
DEVICE=eth0
HWADDR=08:00:27:F9:5B:B9
TYPE=Ethernet
UUID=16b21d21-1ea0-4d4f-9d5d-4c164066cf15
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=static
IPADDR=192.168.2.104
NETMASK=255.255.255.0
GATEWAY=192.168.2.1
DNS1=192.168.2.1        #可选择与主机DNS保持一致，也可使用谷歌的8.8.8.8，根据实际情况切换
DNS2=114.144.114.114     #国内域名服务器
~

After saving and exiting, you can find / There is no need to set it in etc/resolv.conf at all. After service network restart, you can find that there are two DNS resolution IPs in /etc/resolv.conf. After configuring, restart the network, cat /etc/resolv.conf, you can see the following parameters:

[root@localhost /]# cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 192.168.2.1
nameserver 114.144.114.114

DNS resolution setting is successful. At this time, ping the domain name address again and you can ping successfully

It should be emphasized here that it is useless to directly modify the /etc/resolv.conf file. After the network service is restarted, it will be based on /etc/sysconfig/ network-scripts/ifcfg-eth0 to reload the configuration. If ifcfg-eth0 is not configured with DNS, resolv.conf will be flushed and become empty again.

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