resolv.conf的关键字主要有四个，分别是： nameserver //定义DNS服务器的IP地址 domain //定义本地域名 search //定义域名的搜索列表 sortlist //对返回的域名进行排序 下面咱们给出一个/etc/resolv.conf的示例： domain 51osos.com search www.51osos.com 51osos.com nameserver 202.102.192.68 nameserver 202.102.192.69 最主要是nameserver关键字，若是没指定nameserver就找不到DNS服务器，其它关键字是可选的。 nameserver表示解析域名时使用该地址指定的主机为域名服务器。其中域名服务器是按照文件中出现的顺序来查询的,且只有当第一个nameserver没有反应时才查询下面的nameserver。 domain 声明主机的域名。不少程序用到它，如邮件系统；当为没有域名的主机进行DNS查询时，也要用到。若是没有域名，主机名将被使用，删除全部在第一个点( .)前面的内容。 search 它的多个参数指明域名查询顺序。当要查询没有域名的主机，主机将在由search声明的域中分别查找。 domain和search不能共存；若是同时存在，后面出现的将会被使用。 sortlist 容许将获得域名结果进行特定的排序。它的参数为网络/掩码对，容许任意的排列顺序。 “search domainname.com”表示当提供了一个不包括彻底域名的主机名时，在该主机名后添加domainname.com的后 缀；“nameserver”表示解析域名时使用该地址指定的主机为域名服务器。其中域名服务器是按照文件中出现的顺序来查询的。 其中domainname和search可同时存在，也可只有一个；nameserver可指定多个
前提准备：
一台centos7作服务器，两张网卡（桥接and仅主机），一台centos6作客户端，仅主机html
一、[root@centos7 ~]# yum install bind
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
Resolving Dependencies
Installed:
bind.x86_64 32:9.9.4-72.el7
Dependency Installed:
python-ply.noarch 0:3.4-11.el7
Complete!
二、[root@centos7 ~]# rpm -ql bind
/etc/logrotate.d/named
/etc/named
/etc/named.conf
/etc/named.iscdlv.key
/etc/named.rfc1912.zones
/etc/named.root.key
/etc/rndc.conf
/etc/rndc.key
/etc/rwtab.d/named
/etc/sysconfig/named
/run/named
/var/log/named.log
/var/named
/var/named/data
/var/named/dynamic
/var/named/named.ca
/var/named/named.empty
/var/named/named.localhost
/var/named/named.loopback
/var/named/slaves
三、[root@centos7 ~]# rpm -qa "bind*"
bind-libs-lite-9.9.4-72.el7.x86_64
bind-license-9.9.4-72.el7.noarch
bind-9.9.4-72.el7.x86_64
bind-libs-9.9.4-72.el7.x86_64
bind-utils-9.9.4-72.el7.x86_64
四、数据库存放于 /var/named 下 ，且系统默认named已安装，
五、查看named的状态且启动该服务：
[root@centos7 ~]# systemctl status named
● named.service - Berkeley Internet Name Domain (DNS)
Loaded: loaded (/usr/lib/systemd/system/named.service; disabled; vendor preset: disabled)
Active: inactive (dead)
[root@centos7 ~]# systemctl start named
[root@centos7 ~]#
六、查看IP，有IP便可上网
[root@centos7 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:87:73:17 brd ff:ff:ff:ff:ff:ff
inet 192.168.58.254/24 brd 192.168.58.255 scope global noprefixroute ens33
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe87:7317/64 scope link
valid_lft forever preferred_lft forever
3: ens37: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:87:73:21 brd ff:ff:ff:ff:ff:ff
inet 172.20.119.243/16 brd 172.20.255.255 scope global noprefixroute dynamic ens37
valid_lft 83928sec preferred_lft 83928sec
inet6 fe80::23ec:ee7:326a:3f9c/64 scope link noprefixroute
valid_lft forever preferred_lft foreverpython
七、编辑网卡配置文件,添加DNS1=192.168.58.254：
[root@Centos6 ~]# vim /etc/sysconfig/network-scripts/ifcfg-eth0
[root@Centos6 ~]# service network restart
Shutting down interface eth0: Device state: 3 (disconnected)
[ OK ]
Shutting down loopback interface: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: Active connection state: activating
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/6
state: activated
Connection activated
[ OK ]
八、咱们在客户端查看配置文件，会显示主机IP：
[root@Centos6 ~]# cat /etc/resolv.confweb
domain localdomain
search localdomain
nameserver 192.168.58.1
nameserver 192.168.58.254数据库
九、[root@Centos6 ~]# host www.qq.com
;; connection timed out; trying next origin
;; connection timed out; no servers could be reached
此时，咱们去修改配置文件：
十、[root@centos7 ~]# vim /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.
//
// See the BIND Administrator's Reference Manual (ARM) for details about the
// configuration located in /usr/share/doc/bind-{version}/Bv9ARM.htmlvim
options {
listen-on port 53 { localhost; };
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
recursing-file "/var/named/data/named.recursing";
secroots-file "/var/named/data/named.secroots";
allow-query { any; }; centos
/*
- 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
"/etc/named.conf" 61L, 1802C 缓存
十一、使其生效：
[root@centos7 ~]# rndc reload
server reload successful
十二、此时做为客户端，去访问百度，能通，以下：服务器
[root@Centos6 ~]# dig www.baidu.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.68.rc1.el6 <<>> www.baidu.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 60669 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 5, ADDITIONAL: 5 ;; QUESTION SECTION: ;www.baidu.com. IN A ;; ANSWER SECTION: www.baidu.com. 1200 IN CNAME www.a.shifen.com. www.a.shifen.com. 300 IN A 61.135.169.125 www.a.shifen.com. 300 IN A 61.135.169.121 ;; AUTHORITY SECTION: a.shifen.com. 1200 IN NS ns4.a.shifen.com. a.shifen.com. 1200 IN NS ns1.a.shifen.com. a.shifen.com. 1200 IN NS ns2.a.shifen.com. a.shifen.com. 1200 IN NS ns5.a.shifen.com. a.shifen.com. 1200 IN NS ns3.a.shifen.com. ;; ADDITIONAL SECTION: ns5.a.shifen.com. 1200 IN A 180.76.76.95 ns1.a.shifen.com. 1200 IN A 61.135.165.224 ns3.a.shifen.com. 1200 IN A 112.80.255.253 ns2.a.shifen.com. 1200 IN A 220.181.57.142 ns4.a.shifen.com. 1200 IN A 14.215.177.229 ;; Query time: 1018 msec ;; SERVER: 192.168.58.254#53(192.168.58.254) ;; WHEN: Thu Jan 31 19:09:55 2019 ;; MSG SIZE rcvd: 260
分析：此时做为客户端尽管无上外网功能，去ping百度可通，当把7的内网关闭，6没法访问外网，却能够访问7访问过的百度，这是7留下了缓存！当把7的缓存rndc flush 清除掉，6就没法再访问外网了，因此，7就叫只缓存服务器，只利用缓存去访问。网络
[root@centos7 ~]# vim /etc/named.conf
其中的 “ include "/etc/named.rfc1912.zones"; ” 专门存放域名的
查看：[root@centos7 ~]# vim /etc/named.rfc1912.zones
zone "localhost.localdomain" IN {
type master;
file "named.localhost";
allow-update { none; };
};dom
zone "localhost" IN {
type master;
file "named.localhost";
allow-update { none; };
};
zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa" IN {
type master;
file "named.loopback";
allow-update { none; };
};
zone "1.0.0.127.in-addr.arpa" IN {
type master;
file "named.loopback";
allow-update { none; };
};
zone "0.in-addr.arpa" IN {
type master;
file "named.empty";
allow-update { none; };
};
type master; file "magedu.com.zones";
}; 添加进去
[root@centos7 ~]# named-checkconf 来检查语法，无错不提示
[root@centos7 named]# ls
data dynamic named.ca named.empty named.localhost named.loopback slaves
[root@centos7 named]# cp -p named.localhost magedu.com.zone
[root@centos7 named]# id named
uid=25(named) gid=25(named) groups=25(named)
[root@centos7 named]# vim magedu.com.zone
$TTL 1D
@ IN SOA @ rname.invalid. (
0 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimum
NS @
A 127.0.0.1
AAAA :
"magedu.com.zone" 10L, 152C
咱们将其文件修改，变成下图所示：
$TTL 1D
@ IN SOA master admin.magedu.com. (
2019013120 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimun
NS master
master A 192.168.58.254
www CNAME websrv
websrv A 192.168.58.133
blog A 192.168.58.136
@ mx 10 mailsrv1
@ mx 20 mailsrv2
mailsrv1 A 192.168.58.137
mailsrv2 A 192.168.58.138
使用“ named-checkzone ” 来检查语法。
[root@centos7 ~]# rndc reload
server reload successful
[root@Centos6 ~]# cat /etc/resolv.conf
domain localdomain
nameserver 192.168.58.254
搜索结果以下：
[root@Centos6 ~]# dig www.magedu.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.68.rc1.el6 <<>> www.magedu.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15911
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 18
;; QUESTION SECTION:
;www.magedu.com. IN A
;; ANSWER SECTION:
www.magedu.com. 600 IN A 101.200.188.230
;; AUTHORITY SECTION:
magedu.com. 172154 IN NS ns2.alidns.com.
magedu.com. 172154 IN NS ns1.alidns.com.
咱们如今恢复网卡：ifconfig Eth1 up 再添加一个路由：route add default gw 192.168.58.100 (可随便写)ping www.baidu.com 可通但IP每次都不同，说明DNS服务能够作到均衡负载的功能。