linux命令行學習-dig(DNS查詢器)
在web開發中。總要熟悉的就是http協議。而發起一個http開始前最先要經歷的一個過程就是DNS解析。簡單說就是域名怎樣終於解析到實際serverip的過程。
而在研究DNS解析和排除DNS解析類故障問題的時候一個強大的工具就是dig。
和他相應的有個比較傳統的命令nslookup,只是dig作為更新的命令,其強大而簡潔可定制的輸出也使得運維其開發者使用。
實例1(訪問server本地DNSserver查詢根域名server): ~#: dig
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>>
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39027
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 13
;; QUESTION SECTION:
;. IN NS
;; ANSWER SECTION:
. 85715
IN NS a.root-servers.net.
. 85715
IN NS l.root-servers.net.
. 85715
IN NS f.root-servers.net.
. 85715
IN NS d.root-servers.net.
. 85715
IN NS e.root-servers.net.
. 85715
IN NS b.root-servers.net.
. 85715
IN NS c.root-servers.net.
.
. 85715 IN NS k.root-servers.net.
. 85715 IN NS i.root-servers.net.
. 85715 IN NS j.root-servers.net.
. 85715 IN NS h.root-servers.net.
. 85715 IN NS g.root-servers.net.
實例2(百度首頁DNS解析): dig www.baidu.com
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> www.baidu.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15372
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.baidu.com.
;; ANSWER SECTION:
www.baidu.com. 641 IN CNAME www.a.shifen.com.
www.a.shifen.com. 110 IN A 180.97.33.107
www.a.shifen.com. 110 IN A 180.97.33.108
;; Query time: 1 msec
;; SERVER: 192.168.100.52#53(192.168.100.52)
;; WHEN: Wed Aug 13 22:33:59 2014
;; MSG SIZE rcvd: 90
實例3(制定使用google域名server解析百度首頁); dig @8.8.8.8 www.baidu.com
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> @8.8.8.8 www.baidu.com
; (1 server found)
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44033
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.baidu.com. IN
A
;; ANSWER SECTION:
www.baidu.com. 557
IN CNAME
www.a.shifen.com.
www.a.shifen.com. 299
IN A
180.76.3.151
;; Query time: 615 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Wed Aug 13 22:36:36 2014
;; MSG SIZE rcvd: 74
實例4(使用+trace選項查看從根域名server到終於解析到ip的過程): dig www.baidu.com +trace
. 84899
IN NS f.root-servers.net.
. 84899
IN NS d.root-servers.net.
. 84899
IN NS e.root-servers.net.
. 84899
IN NS b.root-servers.net.
. 84899
IN NS c.root-servers.net.
. 84899
IN NS m.root-servers.net.
. 84899
IN NS k.root-servers.net.
. 84899
IN NS i.root-servers.net.
. 84899
IN NS j.root-servers.net.
. 84899
IN NS h.root-servers.net.
. 84899
IN NS g.root-servers.net.
. 84899
IN NS a.root-servers.net.
. 84899
IN NS l.root-servers.net.
;; Received 509 bytes from 192.168.100.52#53(192.168.100.52) in 1 ms
說明:從本地DNSserver得到若幹各根域名server
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 j.gtld-servers.net.
com. 172800
IN NS i.gtld-servers.net.
com. 172800
IN NS k.gtld-servers.net.
com. 172800
IN NS b.gtld-servers.net.
com. 172800
IN NS m.gtld-servers.net.
com. 172800
IN NS f.gtld-servers.net.
com. 172800
IN NS g.gtld-servers.net.
com. 172800
IN NS c.gtld-servers.net.
com. 172800
IN NS d.gtld-servers.net.
com. 172800
IN NS l.gtld-servers.net.
;; Received 503 bytes from 192.5.5.241#53(f.root-servers.net) in 39 ms
說明:選取f.root-servers.net根域名server查詢com域名server
baidu.com. 172800
IN NS
dns.baidu.com.
baidu.com. 172800
IN NS
ns2.baidu.com.
baidu.com. 172800
IN NS
ns3.baidu.com.
baidu.com. 172800
IN NS
ns4.baidu.com.
baidu.com. 172800
IN NS
ns7.baidu.com.
;; Received 201 bytes from 192.5.6.30#53(a.gtld-servers.net) in 360 ms
說明:選取a.gtld-servers.net的com域名server解析baidu.com的域名server
www.baidu.com. 1200
IN CNAME
www.a.shifen.com.
a.shifen.com. 1200
IN NS
ns3.a.shifen.com.
a.shifen.com. 1200
IN NS
ns5.a.shifen.com.
a.shifen.com. 1200
IN NS
ns1.a.shifen.com.
a.shifen.com. 1200
IN NS
ns4.a.shifen.com.
a.shifen.com. 1200
IN NS
ns2.a.shifen.com.
;; Received 228 bytes from 202.108.22.220#53(dns.baidu.com) in 206 ms
說明:通過選擇訪問dns.baidu.com域名server解析到www.baidu.com作為www.a.shifen.com的別名;
於是我們再dig下www.a.shifen.com.
[[email protected] JakQuan]# dig www.a.shifen.com +short
180.97.33.108
180.97.33.107
linux命令行學習-dig(DNS查詢器)