回顾系列:鸟哥的LINUX私房菜（服务器架设篇）:19 DNS

为了适应人类对文字的印象比数字高
1./etc/hosts
2.分布式,阶层式管理架构:DNS系统

DNS采用树型结构框架
完整主机名FQDN
一般顶级域名:.com,.org,.gov等
地区顶级层域名:.uk,.jp,.cn等
每上一层的DNS服务器所记录的信息,其实只有其下一层的主机名而已.
主机名追踪:dig +trace
[t@bjb0541 ~]$ cat /etc/services |grep domain
domain          53/tcp                          # name-domain server
domain          53/udp

DNS标记
    SOA:开始验证
    NS:域名服务器
    A:地址
    PTR:反解指向

客户端相关配置文件:
    /etc/hosts本地解析
    /etc/resolv.conf域名解析
    /etc/nsswitch.conf决定以上两个配置的解析顺序

解析常用命令:host,nslookup,dig,whois

服务器架设:
[root@192-168-174-42 ~]# yum install bind bind-chroot
配置文件:
    /etc/named.conf主配置文件
    /var/named数据库
    /etc/sysconfig/named额外参数
    /var/run/named PID文件

[root@192-168-174-42 ~]# cat /etc/named.conf
//
// named.conf
//
// 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.
//

options {
//      listen-on port 53 { 127.0.0.1; };
        listen-on port 53 { any; };//修改监听所有接口
        //listen-on-v6 port 53 { ::1; };
        directory "/var/named";//数据库目录
        dump-file "/var/named/data/cache_dump.db";//一些统计信息
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        //allow-query     { localhost; };
        allow-query     { any; };

        /*
         - If you are building an AUTHORITATIVE DNS server, do NOT enable recursion.
         - If you are building a RECURSIVE (caching) DNS server, you need to enable
           recursion.
         - If your recursive DNS server has a public IP address, you MUST enable access
           control to limit queries to your legitimate users. Failing to do so will
           cause your server to become part of large scale DNS amplification
           attacks. Implementing BCP38 within your network would greatly
           reduce such attack surface
        */
        recursion yes;//将自己视为客户端
                allow-recursion { localhost; 192.168.184.0/24; };
        forward only;
        forwarders {
                223.5.5.5;
                114.114.114.114;
        };
        dnssec-enable no;
        dnssec-validation no;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";

        pid-file "/run/named/named.pid";
        session-keyfile "/run/named/session.key";
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};
zone "skyovirt.com" IN {
        type master;
        file "named.skyovirt.com";
};
zone "192.168.184.in-addr.arpa" IN {
        type master;
        file "named.192.168.184";
};

include "/etc/named.rfc1912.zones";//默认读取
include "/etc/named.root.key"

[root@192-168-174-42 ~]# cat /var/named/named.skyovirt.com
$TTL 600
$ORIGIN skyovirt.com.
@ IN SOA  skyovirt.com. master.skyovirt.com. (
                                        0 ; serial
                                        3H ; refresh
                                        15M ; retry
                                        1W ; expire
                                        1D ) ; minimum
                                IN NS      skyovirt.com.
skyovirt.com. IN A       192.168.184.11
master.skyovirt.com. IN A       192.168.184.11
ovirthost18.skyovirt.com. IN A       192.168.184.18
ovirthost17.skyovirt.com. IN A       192.168.184.17
ovirthost15.skyovirt.com. IN A       192.168.184.15
ovirthost14.skyovirt.com. IN A       192.168.184.14
ovirthost13.skyovirt.com. IN A       192.168.184.13
ovirt.skyovirt.com. IN A       192.168.184.10
dns.skyovirt.com. IN CNAME   master.skyovirt.com.
[root@192-168-174-42 ~]#

[root@192-168-174-42 ~]# cat /var/named/named.192.168.184
$TTL 600
@ IN SOA  skyovirt.com. master.skyovirt.com. (
                                        0 ; serial
                                        1D ; refresh
                                        1H ; retry
                                        1W ; expire
                                        3H ) ; minimum
@ IN NS      master.skyovirt.com.
11 IN PTR master.skyovirt.com.
18 IN PTR ovirthost18.skyovirt.com.
10 IN PTR ovirt.skyovirt.

重启服务.

[root@192-168-174-42 ~]# service named restart
Redirecting to /bin/systemctl restart  named.service
[root@192-168-174-42 ~]# netstat -lntp |grep named
tcp        0      0 192.168.184.11:53       0.0.0.0:* LISTEN      10210/named
tcp        0      0 127.0.0.1:53            0.0.0.0:* LISTEN      10210/named
tcp        0      0 127.0.0.1:953           0.0.0.0:* LISTEN      10210/named
tcp6       0      0 ::1:53 :::* LISTEN      10210/named
tcp6       0      0 ::1:953 :::* LISTEN      10210/named
[root@192-168-174-42 ~]#

访问外网与自定义域名都OK

[root@192-168-174-42 ~]# dig ovirt.skyovirt.com

; <<>> DiG 9.9.4-RedHat-9.9.4-29.el7_2.2 <<>> ovirt.skyovirt.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30879
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;ovirt.skyovirt.com. IN A

;; ANSWER SECTION:
ovirt.skyovirt.com. 600 IN A       192.168.184.10

;; AUTHORITY SECTION:
skyovirt.com. 600 IN NS      skyovirt.com.

;; ADDITIONAL SECTION:
skyovirt.com. 600 IN A       192.168.184.11

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Mar 10 17:05:16 CST 2016
;; MSG SIZE rcvd: 93

[root@192-168-174-42 ~]# dig www.sky-mobi.com

; <<>> DiG 9.9.4-RedHat-9.9.4-29.el7_2.2 <<>> www.sky-mobi.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62581
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.sky-mobi.com. IN A

;; ANSWER SECTION:
www.sky-mobi.com. 200 IN A       111.1.17.157

;; Query time: 27 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Mar 10 17:05:27 CST 2016
;; MSG SIZE rcvd: 61