redhat 7中DNS 服务器配置与测试

实例：
假设某单位所在的域“gztzy. org"内有三台主机,主机名分别为:jwc. gztzy.org,yds. gztzy.org和 cys.gztzy.org。其中 DNS服务器的地址为192.168.1.3。三台主机的IP地址为192.168.1.4,192.168.1.5和192.168.1.6。现要求 DNS服务器 dns.
gztzy.org可以解析三台主机名和IP地址的对应关系。
分析:根据前面的操作,首先建立主配置文件,设置可以解析的gztzy.org区域。然后建立“gztzy. org"区域文件,并在区域文件中设置SOA、NS 以及A资源记录。最后配置客户端。具体步骤如下:
**

一、配置DNS服务器的静态IP地址

**

[root@localhost 桌面]# vim /etc/sysconfig/network-scripts/ifcfg-eno16777736 
[root@localhost 桌面]# nmtui
[root@localhost 桌面]# systemctl restart network
[root@localhost 桌面]# ifconfig 
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.3  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::20c:29ff:fe80:3fb8  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:80:3f:b8  txqueuelen 1000  (Ethernet)
        RX packets 166  bytes 15574 (15.2 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 275  bytes 29706 (29.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Local Loopback)
        RX packets 539  bytes 48368 (47.2 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 539  bytes 48368 (47.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@localhost Desktop]# df -h
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   38G  2.9G   35G   8% /
devtmpfs               905M     0  905M   0% /dev
tmpfs                  914M  140K  914M   1% /dev/shm
tmpfs                  914M  8.9M  905M   1% /run
tmpfs                  914M     0  914M   0% /sys/fs/cgroup
/dev/sda1              497M  119M  379M  24% /boot
/dev/sr0               3.5G  3.5G     0 100% /run/media/root/RHEL-7.0 Server.x86_64
[root@localhost Desktop]# mkdir /mnt/cdrom && mount /dev/sr0 /mnt/cdrom
mount: /dev/sr0 is write-protected, mounting read-only
[root@localhost Desktop]# vim /etc/yum.repos.d/a.repo
[a]
name=welcome to redhatroom
baseurl=file:///mnt/cdrom
enabled=1
gpgcheck=0
[root@localhost Desktop]# yum install -y bind-chroot.x86_64 
[root@localhost Desktop]# systemctl status named
named.service - Berkeley Internet Name Domain (DNS)
   Loaded: loaded (/usr/lib/systemd/system/named.service; disabled)
   Active: inactive (dead)

[root@localhost Desktop]# systemctl start named
[root@localhost Desktop]# systemctl status named
named.service - Berkeley Internet Name Domain (DNS)
   Loaded: loaded (/usr/lib/systemd/system/named.service; disabled)
   Active: active (running) since Thu 2022-11-03 02:26:41 EDT; 1s ago
  Process: 14259 ExecStart=/usr/sbin/named -u named $OPTIONS (code=exited, status=0/SUCCESS)
  Process: 14258 ExecStartPre=/usr/sbin/named-checkconf -z /etc/named.conf (code=exited, status=0/SUCCESS)
 Main PID: 14261 (named)
   CGroup: /system.slice/named.service
           └─14261 /usr/sbin/named -u named

在Linux系统中，bind服务程序的名称为named。首先需要在/etc目录中找到该服务程序的主配置文件，然后把第11行和第19行的地址均修改为any，分别表示服务器上的所有IP地址均可提供DNS域名解析服务，以及允许所有人对本服务器发送DNS查询请求。

主配置文件（/etc/named.conf）：只有59行，而且在去除注释信息和空行之后，实际有效的参数仅有30行左右，这些参数用来定义bind服务程序的运行。

区域配置文件（/etc/named.rfc1912.zones）：用来保存域名和IP地址对应关系的所在位置。类似于图书的目录，对应着每个域和相应IP地址所在的具体位置，当需要查看或修改时，可根据这个位置找到相关文件。

数据配置文件目录（/var/named）：该目录用来保存域名和IP地址真实对应关系的数据配置文件。

[root@localhost named]# 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.
//

options {
    
    
        listen-on port 53 {
    
     any; };
        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";
        allow-query     {
    
     any; };

1、正向解析实现

[root@localhost named]# vim /etc/named.rfc1912.zones
zone "gztzy.org" IN {
    
    
        type master;
        file "gztzy.org";
        allow-update {
    
     none; };
};
[root@localhost named]# cd /var/named/
[root@localhost named]# ls
data  dynamic  named.ca  named.empty  named.localhost  named.loopback  slaves
[root@localhost named]# cp -a named.localhost gztzy.org
[root@localhost named]# vim gztzy.org 

$TTL 1D	#生存周期为1天
@	IN SOA	gztzy.org.	root.gztzy.org.	(
	#授权信息开始:	#DNS区域的地址	#域名管理员的邮箱(不要用@符号)
			0 ; serial	#更新序列号
			1D ; refresh	#更新时间
			1H ; retry	#重试延时
			1W ; expire	#失效时间
			3H ) ; minimum	#无效解析记录的缓存时间
	NS	dns.gztzy.org.	#域名服务器记录
dns	IN A	192.168.1.3	#地址记录( dns.gztzy.org.)
jwc	IN A	192.168.1.4	#地址记录( jwc.gztzy.org.)
yds	IN A	192.168.1.5	#地址记录( yds.gztzy.org.)
cys	IN A	192.168.1.6	#地址记录( cys.gztzy.org.)

在解析文件中，A记录类型表示将域名指向一个IPv4地址，而AAAA表示将域名指向一个IPv6地址。此外，还有8种记录类型.：

记录类型	作用
A	将域名指向一个IPV4地址
CNAME	将域名指向另外一个域名
AAAA	将域名指向一个IPV6地址
NS	将子域名指定其他DNS服务器解析
MX	将域名指向邮件服务器地址
SRV	记录提供特定的服务的服务器
TXT	文本内容一般为512字节，常作为反垃圾邮件的SPF记录
CAA	CA证书办法机构授权校验
显性URL	将域名重定向到另外一个地址
隐性URL	与显性URL类型，但是会隐藏真实目标地址

[root@localhost named]# named-checkconf				// 检查主配置文件语法或参数的错误。
[root@localhost named]# systemctl restart named
[root@localhost named]# systemctl status named
named.service - Berkeley Internet Name Domain (DNS)
   Loaded: loaded (/usr/lib/systemd/system/named.service; disabled)
   Active: active (running) since 一 2022-10-24 15:05:15 CST; 4s ago
  Process: 46529 ExecStop=/bin/sh -c /usr/sbin/rndc stop > /dev/null 2>&1 || /bin/kill -TERM $MAINPID (code=exited, status=0/SUCCESS)
  Process: 45686 ExecReload=/bin/sh -c /usr/sbin/rndc reload > /dev/null 2>&1 || /bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
  Process: 46539 ExecStart=/usr/sbin/named -u named $OPTIONS (code=exited, status=0/SUCCESS)
  Process: 46537 ExecStartPre=/usr/sbin/named-checkconf -z /etc/named.conf (code=exited, status=0/SUCCESS)
 Main PID: 46543 (named)
   CGroup: /system.slice/named.service
           └─46543 /usr/sbin/named -u named
[root@localhost named]# nslookup 
> jwc.gztzy.org
Server:		192.168.1.3
Address:	192.168.1.3#53

Name:	jwc.gztzy.org
Address: 192.168.1.4
> yds.gztzy.org
Server:		192.168.1.3
Address:	192.168.1.3#53

Name:	yds.gztzy.org
Address: 192.168.1.5
> cys.gztzy.org
Server:		192.168.1.3
Address:	192.168.1.3#53

Name:	cys.gztzy.org
Address: 192.168.1.6
> 

2、反向解析实现

编辑区域配置文件。反向解析是把IP地址解析成域名格式，因此在定义zone（区域）时应该要把IP地址反写，比如原来是192.168.1.0，反写后应该就是1.168.192，而且只需写出IP地址的网络位即可。把下列参数添加至正向解析参数的后面。

[root@localhost named]# vim /etc/named.rfc1912.zones 
zone "gztzy.org" IN {
    
    
        type master;
        file "gztzy.org";
        allow-update {
    
     none; };
};
zone "1.168.192.in-addr.arpa" IN {
    
    
        type master;
        file "192.168.1.arpa";
        allow-update {
    
     none; };
};
[root@localhost named]# ls
data  dynamic  gztzy.org  named.ca  named.empty  named.localhost  named.loopback  slaves
[root@localhost named]# cp -a named.loopback 192.168.1.arpa
[root@localhost named]# vim 192.168.1.arpa 
[root@localhost named]# named-checkconf 
[root@localhost named]# systemctl restart named
[root@localhost named]# systemctl status named
named.service - Berkeley Internet Name Domain (DNS)
   Loaded: loaded (/usr/lib/systemd/system/named.service; disabled)
   Active: active (running) since 一 2022-10-24 15:16:07 CST; 4s ago
  Process: 46787 ExecStop=/bin/sh -c /usr/sbin/rndc stop > /dev/null 2>&1 || /bin/kill -TERM $MAINPID (code=exited, status=0/SUCCESS)
  Process: 45686 ExecReload=/bin/sh -c /usr/sbin/rndc reload > /dev/null 2>&1 || /bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
  Process: 46797 ExecStart=/usr/sbin/named -u named $OPTIONS (code=exited, status=0/SUCCESS)
  Process: 46796 ExecStartPre=/usr/sbin/named-checkconf -z /etc/named.conf (code=exited, status=0/SUCCESS)
 Main PID: 46799 (named)
   CGroup: /system.slice/named.service
           └─46799 /usr/sbin/named -u named

检查测试结果

[root@localhost named]# nslookup 
> 192.168.1.3
Server:		192.168.1.3
Address:	192.168.1.3#53

3.1.168.192.in-addr.arpa	name = dns.gztzy.org.
> 192.168.1.4
Server:		192.168.1.3
Address:	192.168.1.3#53

4.1.168.192.in-addr.arpa	name = jwc.gztzy.org.
> 192.168.1.5
Server:		192.168.1.3
Address:	192.168.1.3#53

5.1.168.192.in-addr.arpa	name = yds.gztzy.org.
> 192.168.1.6
Server:		192.168.1.3
Address:	192.168.1.3#53

6.1.168.192.in-addr.arpa	name = cys.gztzy.org.
> exit

二、部署从服务器

作为重要的互联网基础设施服务，保证DNS域名解析服务的正常运转至关重要，只有这样才能提供稳定、快速且不间断的域名查询服务。在DNS域名解析服务中，从服务器可以从主服务器上获取指定的区域数据文件，从而起到备份解析记录与负载均衡的作用。因此，通过部署从服务器不仅可以减轻主服务器的负载压力，还可以提升用户的查询效率。

应用案例
为ip地址为192.168.1.3的DNS服务器配置从服务器，地址为192.168.1.20。
第1步：在主服务器的区域配置文件中允许该从服务器的更新请求，即修改allow-update {允许更新区域信息的主机地址;};参数，然后重启主服务器的DNS服务程序。

[root@localhost named]# vim /etc/named.rfc1912.zones 
 		zone "gztzy.org" IN {
    
    
        type master;
        file "gztzy.org";
        allow-update {
    
     192.168.1.20; };
};
zone "1.168.192.in-addr.arpa" IN {
    
    
        type master;
        file "192.168.1.arpa";
        allow-update {
    
     192.168.1.20; };
};

第2步：在主服务器上配置防火墙放行规则，让DNS协议流量可以被顺利传递
[root@localhost named]# firewall-config

第3步：在从服务器上安装bind-chroot软件包。修改配置文件，让从服务器也能够对外提供DNS服务，设置从服务器IP地址，测试其与主服务器的网络连通性。

[root@localhost 桌面]# yum install -y bind
[root@localhost 桌面]# ifconfig 
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.20  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::20c:29ff:fe44:2ec6  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:44:2e:c6  txqueuelen 1000  (Ethernet)
        RX packets 744  bytes 66179 (64.6 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2215  bytes 188465 (184.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@localhost named]# vim /etc/named.conf
options {
    
    
        listen-on port 53 {
    
     any; };
        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";
        allow-query     {
    
     any; };

[root@localhost 桌面]# ping 192.168.1.3 -c4       
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.228 ms
64 bytes from 192.168.1.3: icmp_seq=2 ttl=64 time=0.292 ms
64 bytes from 192.168.1.3: icmp_seq=3 ttl=64 time=1.25 ms
64 bytes from 192.168.1.3: icmp_seq=4 ttl=64 time=0.295 ms

--- 192.168.1.3 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3001ms
rtt min/avg/max/mdev = 0.228/0.516/1.252/0.426 ms

第4步：在从服务器中填写主服务器的IP地址与要抓取的区域信息，然后重启服务。注意此时的服务类型应该是slave（从），而不再是master（主）。masters参数后面应该为主服务器的IP地址，而且file参数后面定义的是同步数据配置文件后要保存到的位置，稍后可以在该目录内看到同步的文件。

[root@localhost named]# vim /etc/named.rfc1912.zones 
zone "gztzy.org." IN {
    
    
        type slave;
        masters {
    
    192.168.1.3; };
        file "slaves/gztzy.org.zones";
};
zone "1.168.192.in-addr.arpa" IN {
    
    
        type slave;
        masters {
    
    192.168.1.3; };
        file "slaves/192.168.1.arpa";
};
[root@localhost named]# named-checkconf 
[root@localhost named]# systemctl restart named
root@localhost named]# cd /var/named/slaves/
[root@localhost slaves]# ls
192.168.1.arpa  gztzy.org.zones

第5步：检验解析结果。当从服务器的DNS服务程序在重启后，一般就已经自动从主服务器上同步了数据配置文件，而且该文件默认会放置在区域配置文件中所定义的目录位置中。随后修改从服务器的网络参数，把DNS地址参数修改成192.168.1.20，这样即可使用从服务器自身提供的DNS域名解析服务。最后就可以使用nslookup命令顺利看到解析结果了

[root@localhost slaves]# nslookup 
> 192.168.1.3
Server:		192.168.1.20
Address:	192.168.1.20#53

3.1.168.192.in-addr.arpa	name = dns.gztzy.org.
> yds.gztzy.org
Server:		192.168.1.20
Address:	192.168.1.20#53

Name:	yds.gztzy.org
Address: 192.168.1.5
> exit