介绍

本指南将引导我们完成在CentOS 8/RHEL 8上配置BIND DNS服务器所需的步骤，在CentOS 8/RHEL 8上配置主/从绑定DNS设置。域名系统是用于计算机，服务的分层和分散式命名系统，或者连接到Internet或者专用网络的其他资源。 (维基百科)。它充当Internet的电话簿，因为它为具有关联的FQDN的每台计算机提供地址。

作为TCP/IP参考模型应用层的一部分，DNS在全世界计算机的日常运行中都非常重要。我们将在CentOS8上安装权威的BIND DNS主机和从机，并进行配置，例如添加PTR，A/AAAA记录。

在CentOS 8/RHEL 8上安装绑定DNS服务器

运行以下命令以在CentOS 8/RHEL 8 Linux服务器上安装Bind DNS服务器软件包。

$dnf -y install bind bind-utils vim
CentOS-8 - AppStream                                   1.3 kB/s | 4.3 kB     00:03    
CentOS-8 - Base                                        1.2 kB/s | 3.9 kB     00:03    
CentOS-8 - Extras                                      467  B/s | 1.5 kB     00:03    
Dependencies resolved

在此设置中，请保持SELinux处于强制模式。

$getenforce
Enforcing
THE REASON FOR THIS IS THAT  (Source: RedHat) 
SELinux helps mitigate the damage made by configuration mistakes. Domain Name System (DNS) servers often replicate information between each other in what is known as a zone transfer. Attackers can use zone transfers to update DNS servers with false information. When running the Berkeley Internet Name Domain (BIND) as a DNS server in Red Hat Enterprise Linux, even if an administrator forgets to limit which servers can perform a zone transfer, the default SELinux policy prevents zone files from being updated using zone transfers, by the BIND named daemon itself, and by other processes  (Source: RedHat).

在CentOS 8/RHEL 8上配置BIND DNS授权服务器

让我们配置BIND DNS授权服务器。打开配置文件/etc/named.conf。

我们的DNS服务器具有以下设置。theitroad.local区域(域名)192.168.154.0受管子网192.168.154.94从属服务器的IP 192.168.154.88主服务器的IP

这是named.conf配置文件。

$sudo 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 any since it is an authoritative DNS Publicly available. 
         listen-on-v6 port 53 { any; }; ## You can also set the same for IPv6
         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";
         secroots-file   "/var/named/data/named.secroots";
         recursing-file  "/var/named/data/named.recursing";
 ## Since this will be an authoritative Nameserver, allow query from any host 
        allow-query     { any; };          
        allow-transfer  {192.168.154.94; };     

/*

- 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 no; ## Following Advice from above.     
       dnssec-enable yes;     
       dnssec-validation yes;     
       managed-keys-directory "/var/named/dynamic";     
       pid-file "/run/named/named.pid";     
       session-keyfile "/run/named/session.key";     

/* https://fedoraproject.org/wiki/Changes/CryptoPolicy */    include "/etc/crypto-policies/back-ends/bind.config";
};
 

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

zone "." IN {
         type hint;
         file "named.ca";
};
include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

## Set your ZONE details as shown below for different domains. Set the forward and reverse details. You can set the names of files as you like
 
zone "theitroad.local" IN {
        type master;
        file "theitroad.forward";
        allow-update { none; };
};

## Make sure you follow the rule for reverse zone (154.168.192.in-addr.arpa). [If your IP is 192.168.10.10, It will be 10.168.192.in-addr.arpa]
 
zone "154.168.192.in-addr.arpa" IN {
        type master;
        file "theitroad.reverse";
        allow-update { none; };
};

主服务器192.168.154.88. 请注意，IP应该是公共IP，因为它是权威DNS服务器。

创建区域文件

在named.conf中设置文件后，我们必须创建区域文件并将所有我们希望添加的记录(例如A/AAAA，MX，PTR等)放置。在/var/named /目录中创建文件

$sudo vim /var/named/theitroad.forward

$TTL 86400
 @   IN  SOA     dns1.theitroad.local. root.theitroad.local. (
 # You can use any numerical values for serial number but it is recommended to use [YYYYMMDDnn]
         2019112201  ;Serial
         3600        ;Refresh
         1800        ;Retry
         604800      ;Expire
         86400       ;Minimum TTL
)
         # Set your Name Servers here
         IN  NS      dns1.theitroad.local.
         IN  NS      dns2.theitroad.local.
         # define Name Server's IP address
         IN  A       192.168.154.88
         # Set your Mail Exchanger (MX) Server here
         IN  MX 10   dns1.theitroad.local.

# Set each IP address of a hostname. Sample A records.
dns1     IN  A       192.168.154.88
dns2     IN  A       192.168.154.94
mail1    IN  A       192.168.154.97

为我们在named.conf配置文件中定义的同一域创建相应的反向记录。

$sudo vim /var/named/theitroad.reverse

$TTL 86400
 @   IN  SOA     dns1.theitroad.local. root.theitroad.local. (
         2019112201  ;Serial
         3600        ;Refresh
         1800        ;Retry
         604800      ;Expire
         86400       ;Minimum TTL
 )
         # Set Name Server
         IN  NS      dns1.theitroad.local.
## Set each IP address of a hostname. Sample PTR records.
88      IN  PTR     dns1.theitroad.local.
94      IN  PTR     dns2.theitroad.local.
97      IN  PTR     mail1.theitroad.local.

更改主服务器上的DNS设置

将新的DNS服务器设置为默认名称服务器。打开文件/etc/resolv.conf并添加以下行。确保更换IP以匹配环境。

$sudo vim /etc/resolv.conf  
nameserver 192.168.154.88

允许防火墙上的DNS服务

配置防火墙以允许dns服务。

sudo firewall-cmd --add-service=dns --permanent
sudo firewall-cmd --reload

检查配置是否正常，启动并启用绑定：

sudo named-checkconf
sudo systemctl start named
sudo systemctl enable named

我们已经完成了主绑定DNS服务器。让我们继续配置我们的从服务器。

配置从DNS服务器192.168.154.94

在从属服务器上，安装bind和bind-utils：

sudo dnf -y install bind bind-utils vim

配置从服务器。打开/etc/named.conf并进行相应的编辑

$sudo 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.html

options {
         listen-on port 53 { any; };
         listen-on-v6 port 53 { any; };
         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; }; ## Allows hosts to query Slave DNS
         allow-transfer { none; }; ## Disable zone transfer
          
          /* 
          - 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 
         */
## Since this is a slave, lets allow recursion.
    recursion yes;     
    dnssec-enable yes;     
    dnssec-validation yes;
/* Path to ISC DLV key */
     bindkeys-file "/etc/named.root.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";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

## Let us create zone definitions for both forward and reverse dns lookups.
# The files will be created automatically on the slave.

zone "theitroad.local" IN {
         type slave;
         file "slaves/theitroad.forward";
         masters { 192.168.154.88; }; ## Master server it is receiving DNS Records from
};

zone  "154.168.192.in-addr.arpa" IN {
         type slave;
         file "slaves/theitroad.reverse";
         masters { 192.168.154.88; }; ## Master server it is receiving DNS Records from
};

更改从服务器上的DNS设置

将新的DNS服务器(主服务器和从属服务器)设置为默认名称服务器。打开文件/etc/resolv.conf并添加以下行。确保更换IP以匹配环境

$sudo vim /etc/resolv.conf
nameserver 192.168.154.88
nameserver 192.168.154.94

检查配置是否正常，启动并启用绑定：

sudo named-checkconf
sudo systemctl start named
sudo systemctl enable named

检查/var/named/slaves目录是否已从主服务器传输了区域文件

$ll /var/named/slaves/
total 12
-rw-r--r-- 1 named named 480 Nov 23 14:16 theitroad.forward
-rw-r--r-- 1 named named 492 Nov 23 14:45 theitroad.reverse

证明我们的DNS有效

测试我们的DNS服务器是否解析。我们将使用Windows计算机测试BIND DNS服务器。

如下所示更改窗口的网络详细信息。让DNS反映新DNS服务器。

打开PowerShell或者命令提示符，执行nslookup并测试我们的DNS服务。

我们的BIND DNS可以使用！！如果我们在Linux客户端计算机上执行操作，请编辑/etc/hosts文件以更改DNS配置设置。