A command output explained:
dig www.baidu.com
| <!--?xml version="1.0" encoding="UTF-8" standalone="no"?-->
# dig www.baidu.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6_7.4 <<>> www.baidu.com
;; global options: +cmd
#The above part is controlled by the +[no]cmd option, which displays information such as printing the version of the dig command
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54443
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 5, ADDITIONAL: 5
#The above part +[no]comment option control, display the overall situation of the answer
;; QUESTION SECTION:
;www.baidu.com. IN A
#The above part +[no]question option control, display query, default query A record
;; ANSWER SECTION:
www.baidu.com. 15 IN CNAME www.a.shifen.com.
www.a.shifen.com. 71 IN A 115.239.211.112 (Baidu IP)
www.a.shifen.com. 71 IN A 115.239.210.27 (Baidu IP)
#The above part +[no]answer option control, print the answer, the main record of the domain name
;; AUTHORITY SECTION:
a.shifen.com. 369 IN NS ns1.a.shifen.com.
a.shifen.com. 369 IN NS ns3.a.shifen.com.
a.shifen.com. 369 IN NS ns5.a.shifen.com.
a.shifen.com. 369 IN NS ns2.a.shifen.com.
a.shifen.com. 369 IN NS ns4.a.shifen.com.
#The above part +[no]authority option controls, showing which authoritative servers provide information for the response
;; ADDITIONAL SECTION:
ns1.a.shifen.com. 369 IN A 61.135.165.224
ns2.a.shifen.com. 369 IN A 180.149.133.241
ns3.a.shifen.com. 369 IN A 61.135.162.215
ns4.a.shifen.com. 369 IN A 115.239.210.176
ns5.a.shifen.com. 369 IN A 119.75.222.17
#以上部分+[no]additional选项控制，显示附加信息，主要是权威服务器IP
;; Query time: 0 msec
;; SERVER: 10.202.72.118#53(10.202.72.118)
;; WHEN: Tue Jan 5 10:38:01 2016
;; MSG SIZE rcvd: 260
#以上部分+[no]stats选项控制，显示请求过程的相关信息
|
二 常用方式：
1）获取域名对应IP的精简答案
dig www.baidu.com +short
2）查看各种记录情况
dig www.baidu.com CNAME
3）结合效果
dig www.baidu.com CNAME +short
4）查询大量域名的ip
dig -f /tmp/domain
5）追踪DNS解析
dig www.baidu.com +trace
6）查看ptr记录
dig -x 115.239.211.112