一、熟悉dns的查询流程
- 查询本地DNS缓存：包括浏览器、操作系统、网关等。
- 向递归DNS服务器发起查询。
- 递归DNS服务器查询根域名服务器。
- 查询顶级域名服务器。
- 查询权威DNS服务器。
看个示例：
homework@whobotai-bj-jump:~$ dig +trace hangdaowangluo.com ; <<>> DiG 9.18.28-1~deb12u2-Debian <<>> +trace hangdaowangluo.com ;; global options: +cmd . 3 IN NS b.root-servers.net. . 3 IN NS j.root-servers.net. . 3 IN NS k.root-servers.net. . 3 IN NS g.root-servers.net. . 3 IN NS m.root-servers.net. . 3 IN NS i.root-servers.net. . 3 IN NS l.root-servers.net. . 3 IN NS a.root-servers.net. . 3 IN NS e.root-servers.net. . 3 IN NS c.root-servers.net. . 3 IN NS d.root-servers.net. . 3 IN NS f.root-servers.net. . 3 IN NS h.root-servers.net. ;; Received 433 bytes from 172.25.15.29#53(172.25.15.29) in 0 ms ## 返回根域名服务器，共13组 com. 172800 IN NS b.gtld-servers.net. com. 172800 IN NS g.gtld-servers.net. com. 172800 IN NS m.gtld-servers.net. com. 172800 IN NS c.gtld-servers.net. com. 172800 IN NS a.gtld-servers.net. com. 172800 IN NS e.gtld-servers.net. com. 172800 IN NS h.gtld-servers.net. com. 172800 IN NS d.gtld-servers.net. com. 172800 IN NS f.gtld-servers.net. com. 172800 IN NS k.gtld-servers.net. com. 172800 IN NS i.gtld-servers.net. com. 172800 IN NS j.gtld-servers.net. com. 172800 IN NS l.gtld-servers.net. com. 86400 IN DS 19718 13 2 8ACBB0CD28F41250A80A491389424D341522D946B0DA0C0291F2D3D7 71D7805A com. 86400 IN RRSIG DS 8 1 86400 20250625050000 20250612040000 53148 . azDsshVlQyq9Ix5feihYIM5Hw4SzD/YO0Stm/abvmjTL9VQM5o1/+Mk6 XRu2CPWrEIy8Y3E2Jc6tSFO9tYosid+jYowNJxf1aFj950MEsBIszgzg gvShTFcg7i/Lmf2RtCfpE2aGn4XFjiyutNOH6s25L2D1Qi4hGP68tmB4 +xN53eNhPMxbx6oPh7OsoZYS5aCPWxygNtY/kTICjRTOnbN0qzy7Fftq x6Esqj4pYe2rL0bd9L/DwF1ds0nnYNwdylY0NtLzcroFw64+HGMyDXHD vH0UK1nQ+F3EpTSuZ7tKWL4MYVFnZyHeGcDBjknGgqReZzFZFQ8OhUJ7 UDwDvw== ;; Received 1178 bytes from 202.12.27.33#53(m.root-servers.net) in 108 ms ## 从m.root-servers.net中返回顶级域名服务器 hangdaowangluo.com. 172800 IN NS dns11.hichina.com. hangdaowangluo.com. 172800 IN NS dns12.hichina.com. CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 900 IN NSEC3 1 1 0 - CK0Q3UDG8CEKKAE7RUKPGCT1DVSSH8LL NS SOA RRSIG DNSKEY NSEC3PARAM CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 900 IN RRSIG NSEC3 13 2 900 20250616002600 20250608231600 40097 com. v9YfYkAsxAUBAA/CYew7yh9jJry91qCO8ZCDjWQUXJryhWSAeEcQct2G eIuRkL6pvp2BWcyYktSqtorOuLkR2Q== QMCL7DFDLIA96DAA5LTI30LP0E3FSF3B.com. 900 IN NSEC3 1 1 0 - QMCLB0EE9F2UU6AN21S02HATCV0CO32A NS DS RRSIG QMCL7DFDLIA96DAA5LTI30LP0E3FSF3B.com. 900 IN RRSIG NSEC3 13 2 900 20250616003715 20250608232715 40097 com. n3W5mcRxmOJfpu5VMmytFJYgzrTrQAR1WAdbBezvVC4N70QfX/cJAHWA ofTflvULSIbTw1UO+t7rkO5+wps06w== ;; Received 764 bytes from 192.31.80.30#53(d.gtld-servers.net) in 164 ms ## 从顶级域名服务器d.gtld-servers.net中返回权威服务器。 hangdaowangluo.com. 600 IN A 47.94.240.36 ;; Received 63 bytes from 47.118.199.202#53(dns11.hichina.com) in 28 ms ## 从权威服务器dns11.hichina.com找到了域名的IP
二、常用命令
1、/usr/bin/resolvectl statistics
查询本地的缓存记录：