DNS domain name space

DNS Naming system , It's a tree growing upside down , That is to say, the root grows to the sky .

The management of domain name space is feudal , Is it royal land in the world , It's the root . The following top-level domain is the local king . Each organization is responsible for naming and managing the domains assigned to it and the sub domains under it , Manage the hostname and IP Mapping . The task of management and interpretation is through DNS Server , frequently-used DNS The server is BIND, It was originally DARPA Funded a graduate program at the University of Berkeley .
centos8 Installation on ：yum install bind bind-utils

When A The host wants to access B When it's on the mainframe , Inquire about DNS The path of the server is like this .
there A The host and B Hosts are all hosts or servers managed under the domain .

If the computer of an ordinary user wants to access a host , For example, the computer that accesses the Internet in the family , Or there is no domain management computer in the company （ Working group mode ） To access a host ,DNS The process of domain name resolution is like this ：

According to this parsing process , If the root server is down , Then domain name network access paralysis will occur .

DNS There are main types of 、 from 、 Cache and other types , The configuration file has a master configuration file 、 Regional data files, etc .
bind Master profile /etc/named.conf, The default content is as follows ：

// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS server as a caching only nameserver (as a localhost DNS resolver only). See /usr/share/doc/bind*/sample/ for example named configuration files.//  This shows that only localhost DNS resolver, So we have to change options {    //listen-on port 53 { 127.0.0.1; };    listen-on port 53 { any; };    listen-on-v6 port 53 { ::1; };    directory   "/var/named";    dump-file   "/var/named/data/cache_dump.db";    statistics-file "/var/named/data/named_stats.txt";    memstatistics-file "/var/named/data/named_mem_stats.txt";    secroots-file   "/var/named/data/named.secroots";    recursing-file  "/var/named/data/named.recursing";    //allow-query { localhost; };    allow-query     { any; };    recursion yes;    dnssec-enable yes;    //dnssec-validation yes;    dnssec-validation no;    managed-keys-directory "/var/named/dynamic";    pid-file "/run/named/named.pid";    session-keyfile "/run/named/session.key";    /* https://fedoraproject.org/wiki/Changes/CryptoPolicy */    include "/etc/crypto-policies/back-ends/bind.config";};logging {        channel default_debug {                file "data/named.run";                severity dynamic;        };};zone "." IN {    type hint;    file "named.ca";};//include "/etc/named.rfc1912.zones";include "/etc/named.mine.zones";include "/etc/named.root.key";

/var/named/├── data├── dynamic├── slaves├── named.ca├── named.empty├── named.localhost└── named.loopback

To be continued