Which is the linux dns configuration file?

The linux dns configuration file is "/etc/resolv.conf". This configuration file is used to configure the DNS client. It contains the domain name search order of the host and the address of the DNS/server. Each line includes a keyword and one or more spaces separated parameters.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

Which is the linux dns configuration file?

In Linux, the configuration file of the DNS server is "/etc/resolv.conf".

/etc/resolv.conf file is used to configure the DNS client. It contains the domain name search order of the host and the address of the DNS/server. Each line includes a keyword and one or more space-separated parameters. .

Basic introduction to DNS:

1. Introduction to DNS

DNS (Domain Name System) means domain name resolution server. It is an application layer protocol. A service of the Internet. As a distributed database that maps domain names and IP addresses to each other, it can make people access the Internet more conveniently. The DNS service uses port 53 of TCP and UDP. TCP port 53 is used to connect to the DNS server, and UDP port 53 is used to resolve DNS. The length limit for each level of domain name is 63 characters, and the total length of the domain name cannot exceed 253 characters.

2. The role of DNS

Forward analysis: Find the corresponding IP address based on the domain name

Reverse analysis: Check the corresponding domain name based on the IP address

3. DNS domain name structure

1) The root domain

is located at the top level of the tree structure, and is represented by "."

2) Top-level domain

generally represents a type of organization or country region

3) Second-level domain

is used to indicate A specific organization within the top-level domain. The second-level domain names under the national top-level domain are uniformly managed by national departments. For example: .net.cn

. .edu.cn

. com.cn

4) Sub-domain/third-level domain

The domains at all levels created under the second-level domain are collectively called sub-domains. Each organization or user can freely apply to register their own domain name

5) Host

The host is located at the bottom of the domain name space and is a specific computer

Host name: www

                                                                                                                                                                                                                                                          # There is a many-to-one relationship between domain names and IP addresses. An IP address does not necessarily correspond to only one domain name, and a domain name can only correspond to one IP address

4. DNS server type

1 ) The main domain name server

is responsible for maintaining all domain name information in a region. It is the authoritative information source for all specific information, and the data can be modified. When building a primary domain name server, you need to create the address data file for the area you are responsible for.

2) Secondary domain name server

When the primary domain name server fails, shuts down, or is overloaded, the secondary domain name server provides domain name resolution services as a backup service. The resolution results provided from the domain name server are not determined by yourself, but come from the main domain name server. When building a secondary domain name server, you need to specify the location of the primary domain name server so that the server can automatically synchronize the region's address database.

3) Cache domain name server

Only provides the caching function of domain name resolution results. The purpose is to improve query speed and efficiency, but there is no domain name database. It fetches the result of each domain name server query from a remote server and caches it to respond to subsequent queries for the same information. Caching name servers are not authoritative servers because all information provided is indirect. When building a cache domain name server, you must set the root domain or specify other DNS servers as the resolution source.

4) Forwarding domain name server

is responsible for local queries of all non-local domain names. After the forwarding domain name server receives the query request, it searches it in its cache. If it cannot find it, it forwards the request to the specified domain name server in sequence until the result is found, otherwise it returns a result that cannot be mapped.

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