Linux下DNS缓存服务器的搭建
CentOS 6.10搭建本地DNS缓存服务器
系统环境
1 [root@test ~]# cat /etc/redhat-release 2 CentOS release 6.10 (Final) 3 [root@test ~]# uname -r 4 2.6.32-754.el6.x86_64 5 [root@test ~]# getenforce 6 Disabled 7 [root@test ~]# /etc/init.d/iptables stop
安装DNS服务包
1 [root@test ~]# yum -y install bind bind-libs bind-utils
修改配置文件
bind DNS服务的主配置文件是/etc/named.conf，默认情况下是已经启用了本地缓存功能。不过为了加快查询速度和解决一些报错，通常情况下我们还需要一些调整。
1 [root@test ~]# cat /etc/named.conf 2 // 3 // named.conf 4 // 5 // Provided by Red Hat bind package to configure the ISC BIND named(8) DNS 6 // server as a caching only nameserver (as a localhost DNS resolver only). 7 // 8 // See /usr/share/doc/bind*/sample/ for example named configuration files. 9 // 10 11 options { 12 listen-on port 53 { any; }; 13 // listen-on-v6 port 53 { ::1; }; 14 directory "/var/named"; 15 dump-file "/var/named/data/cache_dump.db"; 16 statistics-file "/var/named/data/named_stats.txt"; 17 memstatistics-file "/var/named/data/named_mem_stats.txt"; 18 allow-query { any; }; 19 recursion yes; 20 forworders { 114.114.114.114; 8.8.8.8; }; 21 dnssec-enable no; 22 dnssec-validation yes; 23 24 /* Path to ISC DLV key */ 25 bindkeys-file "/etc/named.iscdlv.key"; 26 27 managed-keys-directory "/var/named/dynamic"; 28 }; 29 30 logging { 31 channel default_debug { 32 file "data/named.run"; 33 severity dynamic; 34 }; 35 }; 36 37 zone "." IN { 38 type hint; 39 file "named.ca"; 40 }; 41 42 include "/etc/named.rfc1912.zones"; 43 include "/etc/named.root.key";
此时已完成了一个本地缓存服务器的配置。
测试本地缓存服务器
1 [root@test ~]# ip a 2 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 3 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 4 inet 127.0.0.1/8 scope host lo 5 inet6 ::1/128 scope host 6 valid_lft forever preferred_lft forever 7 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 8 link/ether 00:0c:29:18:98:2b brd ff:ff:ff:ff:ff:ff 9 inet 10.0.0.77/24 brd 10.0.0.255 scope global eth0 10 inet6 fe80::20c:29ff:fe18:982b/64 scope link 11 valid_lft forever preferred_lft forever 12 13 [root@test ~]# cat /etc/resolv.conf 14 nameserver 10.0.0.77 15 16 [root@test ~]# nslookup 17 > www.baidu.com 18 Server: 10.0.0.77 19 Address: 10.0.0.77#53 20 21 Non-authoritative answer: 22 www.baidu.com canonical name = www.a.shifen.com. 23 Name: www.a.shifen.com 24 Address: 115.239.210.27 25 Name: www.a.shifen.com 26 Address: 115.239.211.112 27 [root@test ~]# ping baidu.com 28 PING baidu.com (220.181.57.216) 56(84) bytes of data. 29 64 bytes from 220.181.57.216: icmp_seq=1 ttl=128 time=30.5 ms 30 64 bytes from 220.181.57.216: icmp_seq=2 ttl=128 time=30.9 ms
禁用IPv6解析
1）注释主配置文件的IPv6选项
2）修改/etc/sysconfig/named文件
OPTIONS=”whatever” 改为 OPTIONS=”-4″
# 注意OPTIONS选项的值可以是：whatever、-4、-6中的一个
禁用dnssec功能
为什么禁用？
1 Dec 20 14:52:22 test named[2159]: error (insecurity proof failed) resolving 'in-addr.arpa/DNSKEY/IN': 114.114.114.114#53 2 Dec 20 14:52:22 test named[2159]: validating @0x7fc654456820: 123.in-addr.arpa SOA: got insecure response; parent indicates it should be secure 3 Dec 20 14:52:22 test named[2159]: error (no valid RRSIG) resolving '125.123.in-addr.arpa/DS/IN': 114.114.114.114#53 4 Dec 20 14:52:22 test named[2159]: validating @0x7fc6544574b0: 123.in-addr.arpa DNSKEY: got insecure response; parent indicates it should be secure
dnssec功能会对解析结果进行验证，是否为权威解答，不是就会报错，虽然不影响使用，但是看着不爽。
怎么禁用？
修改主配置文件
1 # vim /etc/named.conf 2 dnssec-enable no; 3 dnssec-validation no;
创建本地DNS服务器，解析本地DNS记录
我们只需要在上面的DNS缓存服务器上增加个zone区域文件即可。
1 # vim /etc/named.rfc1912.zones 2 # 最后面加上这个zone 3 zone "test" IN { 4 type master; 5 file "test.zone"; 6 allow-update { none; }; 7 };
# 创建对应的test.zone文件（配置解析记录）
1 [root@test ~]# cp -a /var/named/named.localhost /var/named/test.zone
把要解析的记录写进该文件
重启DNS服务即可
listen与query项出于安全考虑，也可以将any设置为192.168.1.0/24这样的格式；
dump-file项需要注意的是默认情况下dns本地缓存数据都是存放在内存中，只有在使用rndc dumpdb -all 时才会将内存中的数据保存在本地盘中，保存的路径就是该项配置的名称；
启用forwarders查询会减少本地流量的浪费，直接从转发的服务器上查询的结果返回；
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