The role of /etc/resolv.conf

Backstory:

Have we ever had such an experience: when we use a browser to surf the Internet, we can't get on, but QQ can get on it.Why?There is a problem with dns, one of the ways is to solve this problem by configuring /etc/resolv.conf.

What is it?

/etc/resolv.conf It is the DNS client configuration file, which is used to set the IP address and DNS domain name of the DNS server, and also contains the domain name search order of the host.This file is a configuration file used by resolvers (a library that resolves IP addresses from hostnames).

nameserver #Define the IP address of the DNS serverdomain #define the local domain namesearch #Define the search list of domain namessortlist #sort the returned domain names

An example of /etc/resolv.conf:

​domain test.comsearch www.test.com test.comnameserver 202.96.128.86nameserver 202.96.128.166​

The most important is the nameserver keyword. If the nameserver is not specified, the DNS server cannot be found. Other keywords are optional.

nameserver - Indicates that the host specified by this address is the domain name server when resolving the domain name.The domain name servers are queried in the order in which they appear in the file, and the following nameservers are queried only when the first nameserver does not respond.
domain Declare the domain name of the host.It is used by many programs, such as mail systems; it is also used when doing DNS queries for hosts that do not have a domain name.If there is no domain name, the hostname will be used, removing everything before the first dot ( .).
search Its multiple parameters specify the domain name search order.When querying a host without a domain name, the host will be looked up separately in the domain declared by search.
domain and search cannot coexist; if both exist, the latter will be used.
sortlist Allows specific sorting of the domain name results.Its argument is a net/mask pair, allowing any sort order

Priority: dns cache>hosts>dns service

Steps of DNS resolution:

1. Find /etc/hosts

2. Find the domain name according to the nameserver

3. If the domain name cannot be found on the nameserver, perform search completion and take 1~2 steps again

Recently encountered wget: unable to resolve host address `******'

Workaround: vim /etc/resolv.conf

Add nameserver 114.114.114.114

The ips that can usually be configured are:

114.114.114.114

119.29.29.29

223.5.5.5

Reference Analysis of the role of /etc/hosts and /etc/resolv.conf_Nick_9705's blog-CSDN blog

Reprint: /etc/What resolv.conf does - take a look