Linux DNS 笔记

贡献者： addis

基本原理参考《30 张图解网络》系列教程
domain name system (DNS)
nslookup 域名 可以查看用于解析域名的服务器，在 ubuntu22.04 上会返回 127.0.0.53。这实际上是本机的 systemd-resolved
操作系统会使用 /etc/resolv.conf 文件中可以配置 linux 的 dns 服务器，但如果用了 systemd-resolved，该文件实际上是一个软链，自动生成，不建议修改。
如果使用 WSL 那么 /etc/resolv.conf 是由 windows 自动生成的，见开头的注释。
如果没用 resolved 的话，可以在该文件里面添加若干行类似 nameserver 8.8.8.8 的设置，其中 8.8.8.8 是 google 提供的 DNS 服务。
dig +trace +nodnssec 域名 可以看到每一个域名服务器的 ip 和详细信息。*.root-servers.net 是跟域名服务器，tld 是顶级域名（top level domain）服务器。顶级域名就是 .com，.net 这些
resolvectl query 域名 可以获取域名以及解析的信息

1. DNS record 的类型

A records map domain names to IPv4 addresses.
AAAA record is the IPv6 equivalent of an A record
CNAME Redirects a domain to a different domain
MX Provides the domain names of mail servers that receive emails on behalf of a domain
SOA Provides important details about a DNS zone; required for every DNS zone
TXT Provides any type of descriptive information in text format

Zone：DNS zones need an SOA。a 'zone' is an area of control over namespace. A zone can include a single domain name, one domain and many subdomains, or many domain names. In some cases, 'zone' is essentially equivalent with 'domain,' but this is not always true.
start of authority (SOA) record：stores important information about a domain or zone
A zone file is a plain text file stored in a DNS server that contains an actual representation of the zone and contains all the records for every domain within the zone.
A zone serial number is a version number for the SOA record
A DNS zone transfer is the process of sending DNS record data from a primary nameserver to a secondary nameserver.