一、背景介绍
在日常工作中，为解决内网域名解析问题，时长会配置DNS服务来提供解析。这时DNS服务就起到了为所有内部服务提供连通的基础，变得非常重要了。所以在服务启动后还是应该考虑服务的高可用和数据的完整性。
网友有很多LVS+Keepalived+Bind的负载均衡高可用的解决方案，非常不错。不过自建DNS常用在公司内部平台之间的调用，所以负载均衡的意义并不是太大。当然，高可用还是需要保证的。本文章介绍通过Keepalived+Bind实现高可用主从同步DNS服务
二、基础环境
Master DNS：10.61.100.51
Slave DNS：10.61.100.52
VIP：10.61.100.50
三、bind配置
3.1、安装bind（主从）
# yum install bind bind-chroot 安装包的作用就不做过多的介绍了
安装完成后会生成下面的文件
[root@ip-10-61-100-51 ~]# ll /var/named/chroot/ 总用量 20 drwxr-x--- 2 root named 4096 7月 11 16:55 dev drwxr-x--- 5 root named 4096 7月 11 19:31 etc drwxr-xr-x 2 root root 4096 7月 11 19:31 lib64 drwxr-xr-x 3 root root 4096 7月 11 16:55 usr drwxr-x--- 6 root named 4096 7月 11 16:55 var [root@ip-10-61-100-51 ~]# ll /etc/named.conf -rw-r----- 1 root named 1311 7月 11 17:39 /etc/named.conf 其中/etc/named.conf其实就是/var/named/chroot/etc/named.conf，在启动后会在/var/named/chroot/etc生成相关配置文件。
3.2、创建named.conf配置文件（主从都要配置，从配置在下面给出）
vim /etc/named.conf
options {
directory "/var/named";
listen-on { any; };
version "[wowoohr-1.0]";
forwarders { 202.96.209.5;
114.114.114.114;
};
recursion yes;
allow-query {0.0.0.0/0;};
};
logging{
channel default_log {
file "/etc/log/dns-default.log" versions 10 size 1m;
severity info;
};
channel lamer_log {
file "/etc/log/dns-lamer.log" versions 3 size 1m;
severity info;
print-severity yes;
print-time yes;
print-category yes;
};
channel query_log {
file "/etc/log/dns-query.log" versions 10 size 10m;
severity info;
};
channel security_log {
file "/etc/log/dns-security.log" versions 3 size 1m;
severity info;
print-severity yes;
print-time yes;
print-category yes;
};
category lame-servers { lamer_log; };
category security { security_log; };
category queries { query_log; };
category default { default_log; };
};
zone "." {
type hint;
file "/etc/named.root";
};
zone "myshebao.com" {
type master;
file "/etc/master/test.com.zone ";
allow-transfer { 10.61.100.52; };
};
3.3、创建named.root配置文件（主从都要配置且配置一样，故从配置不在给出）
[root@ip-10-61-100-51 etc]# cat named.root ; This file holds the information on root name servers needed to ; initialize cache of Internet domain name servers ; ; This file is made available by InterNIC ; under anonymous FTP as ; file /domain/named.root ; on server FTP.INTERNIC.NET ; -OR- RS.INTERNIC.NET ; ; last update: Jan 29, 2004 ; related version of root zone: 2004012900 ; ; ; formerly NS.INTERNIC.NET ; . 3600000 IN NS A.ROOT-SERVERS.NET. A.ROOT-SERVERS.NET. 3600000 A 198.41.0.4 ; ; formerly NS1.ISI.EDU ; . 3600000 NS B.ROOT-SERVERS.NET. B.ROOT-SERVERS.NET. 3600000 A 192.228.79.201 ; ; formerly C.PSI.NET ; . 3600000 NS C.ROOT-SERVERS.NET. C.ROOT-SERVERS.NET. 3600000 A 192.33.4.12 ; ; formerly TERP.UMD.EDU ; . 3600000 NS D.ROOT-SERVERS.NET. D.ROOT-SERVERS.NET. 3600000 A 128.8.10.90 ; ; formerly NS.NASA.GOV ; . 3600000 NS E.ROOT-SERVERS.NET. E.ROOT-SERVERS.NET. 3600000 A 192.203.230.10 ; ; formerly NS.ISC.ORG ; . 3600000 NS F.ROOT-SERVERS.NET. F.ROOT-SERVERS.NET. 3600000 A 192.5.5.241 ; ; formerly NS.NIC.DDN.MIL ; . 3600000 NS G.ROOT-SERVERS.NET. G.ROOT-SERVERS.NET. 3600000 A 192.112.36.4 . 3600000 NS E.ROOT-SERVERS.NET. E.ROOT-SERVERS.NET. 3600000 A 192.203.230.10 ; ; formerly NS.ISC.ORG ; . 3600000 NS F.ROOT-SERVERS.NET. F.ROOT-SERVERS.NET. 3600000 A 192.5.5.241 ; ; formerly NS.NIC.DDN.MIL ; . 3600000 NS G.ROOT-SERVERS.NET. G.ROOT-SERVERS.NET. 3600000 A 192.112.36.4 ; ; formerly AOS.ARL.ARMY.MIL ; . 3600000 NS H.ROOT-SERVERS.NET. H.ROOT-SERVERS.NET. 3600000 A 128.63.2.53 ; ; formerly NIC.NORDU.NET ; . 3600000 NS I.ROOT-SERVERS.NET. I.ROOT-SERVERS.NET. 3600000 A 192.36.148.17 ; ; operated by VeriSign, Inc. ; . 3600000 NS J.ROOT-SERVERS.NET. J.ROOT-SERVERS.NET. 3600000 A 192.58.128.30 ; ; operated by RIPE NCC ; . 3600000 NS K.ROOT-SERVERS.NET. K.ROOT-SERVERS.NET. 3600000 A 193.0.14.129 ; ; operated by ICANN ; . 3600000 NS L.ROOT-SERVERS.NET. L.ROOT-SERVERS.NET. 3600000 A 198.32.64.12 ; ; operated by WIDE ; . 3600000 NS M.ROOT-SERVERS.NET. M.ROOT-SERVERS.NET. 3600000 A 202.12.27.33 ; End of File
3.4、根据配置文件创建相关目录（主配置）
[root@ip-10-61-100-51 etc]# cd /var/named/chroot/etc/ [root@ip-10-61-100-51 etc]# mkdir log master [root@ip-10-61-100-51 etc]# chown named:named log/ -R
3.5、创建zone区域文件（主配置）
[root@ip-10-61-100-51 etc]# vim master/test.com.zone $TTL 1D @ IN SOA ns1.test.com. yull.test.com. ( 2017071104 ; serial 1D ; refresh 1H ; retry 1W ; expire 3H ) ; minimum IN NS ns1.test.com. IN NS ns2.test.com. ns1 IN A 10.61.100.51 ns2 IN A 10.61.100.52 redis IN A 10.61.100.51 db IN A 10.61.100.53
3.6、启动named服务（主配置）
# service named start
3.7、从服务器named.conf配置。注意从服务器也需要named.root文件
[root@ip-10-61-100-52 ~]# cat /etc/named.conf
options {
directory "/var/named";
listen-on { any; };
version "[wowoohr-1.0]";
forwarders { 202.96.209.5;
114.114.114.114;
};
recursion yes;
allow-query {0.0.0.0/0;};
};
logging{
channel default_log {
file "/etc/log/dns-default.log" versions 10 size 1m;
severity info;
};
channel lamer_log {
file "/etc/log/dns-lamer.log" versions 3 size 1m;
severity info;
print-severity yes;
print-time yes;
print-category yes;
};
channel query_log {
file "/etc/log/dns-query.log" versions 10 size 10m;
severity info;
};
channel security_log {
file "/etc/log/dns-security.log" versions 3 size 1m;
severity info;
print-severity yes;
print-time yes;
print-category yes;
};
category lame-servers { lamer_log; };
category security { security_log; };
category queries { query_log; };
category default { default_log; };
};
zone "." {
type hint;
file "/etc/named.root";
};
zone "myshebao.com" {
type slave;
file "/etc/slave/test.com.zone";
masters {
10.61.100.51;
};
allow-transfer { none; };
};
3.8、创建相关目录文件（从）
[root@ip-10-61-100-52 etc]# cd /var/named/chroot/etc/ [root@ip-10-61-100-52 etc]# mkdir log slave [root@ip-10-61-100-52 etc]# chown named:named log/ -R
3.9、启动named服务（从）
# service named start
如成功配置，则会在从的/var/named/chroot/etc/slave下同步test.com.zone配置文件。
四、Keepalived高可用配置
4.1、安装Keepalived（主从）
# yum -y install keepalived
4.2、修改配置文件
设计思路：
当 Master 与 Slave 均运作正常时, Master负责服务，Slave负责Standby；
当 Master 挂掉，Slave 正常时, Slave接管服务；
当 Master 恢复正常，恢复Master身份
然后依次循环。需要注意的是修改数据只能在Master修改。
[root@ip-10-61-100-51 etc]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 192.168.200.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_dns {
script "/etc/keepalived/scripts/dns_check.sh"
interval 2
}
vrrp_instance V_DNS {
state MASTER
interface eth0
virtual_router_id 153
priority 100 #从服务器修改为80
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
chk_dns
}
virtual_ipaddress {
10.61.100.50
}
notify_master /etc/keepalived/scripts/dns_master.sh
notify_backup /etc/keepalived/scripts/dns_backup.sh
notify_fault /etc/keepalived/scripts/dns_fault.sh
notify_stop /etc/keepalived/scripts/dns_stop.sh
}
上述中的脚本因为Keepalived在转换状态时会依照状态来呼叫：
通过dns_check.sh来检测服务可用性
当进入Master状态时会呼叫notify_master
当进入Backup状态时会呼叫notify_backup
当发现异常情况时进入Fault状态呼叫notify_fault
当Keepalived程序终止时则呼叫notify_stop
4.3、编辑相关脚本（主从）
# vim /etc/keepalived/scripts/dns_check.sh #!/bin/bash ALIVE=`netstat -ntpl |grep "53"` if [ $? == 0 ];then exit 0 else exit 1 fi
# vim /etc/keepalived/scripts/dns_master.sh LOGFILE="/var/log/keepalived-dns-state.log" echo "[master]" >> $LOGFILE date >> $LOGFILE echo "Being master...." >> $LOGFILE 2>&1 echo "Run reload cmd ..." >> $LOGFILE service named reload >> $LOGFILE 2>&1
# vim /etc/keepalived/scripts/dns_backup.sh LOGFILE="/var/log/keepalived-dns-state.log" echo "[backup]" >> $LOGFILE date >> $LOGFILE service named reload >> $LOGFILE 2>&1 echo "Being slave...." >> $LOGFILE 2>&1
# vim /etc/keepalived/scripts/dns_fault.sh #!/bin/bash LOGFILE=/var/log/keepalived-dns-state.log echo "[fault]" >> $LOGFILE date >> $LOGFILE
# vim /etc/keepalived/scripts/dns_stop.sh #!/bin/bash LOGFILE=/var/log/keepalived-dns-state.log echo "[stop]" >> $LOGFILE date >> $LOGFILE
4.4、给脚本都加上可执行权限：
# sudo chmod +x /etc/keepalived/scripts/*.sh
4.5、启动Keepalived服务
# service keepalived start
五、验证
[root@ip-10-61-100-51 etc]# netstat -ntpl |grep 53 tcp 0 0 10.61.100.50:53 0.0.0.0:* LISTEN 12314/named tcp 0 0 10.61.100.51:53 0.0.0.0:* LISTEN 12314/named tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 12314/named tcp 0 0 127.0.0.1:953 0.0.0.0:* LISTEN 12314/named tcp 0 0 ::1:953 :::* LISTEN 12314/named
[root@ip-10-61-100-52 ~]# vim /etc/keepalived/scripts/dns_stop.sh [root@ip-10-61-100-52 ~]# netstat -ntpl |grep 53 tcp 0 0 10.61.100.52:53 0.0.0.0:* LISTEN 8220/named tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 8220/named tcp 0 0 127.0.0.1:953 0.0.0.0:* LISTEN 8220/named tcp 0 0 ::1:953 :::* LISTEN 8220/named
可以看到VIP已经绑定在Master上，同时可以模拟Master挂掉。VIP会自动漂移到Slave上，带Master恢复后，会再次回到Master上，保证服务可用性。