DNSmasq是一个小巧且方便地用于配置DNS和DHCP的工具，适用于小型网络。它提供了DNS功能和可选择的DHCP功能可以取代dhcpd(DHCPD服务配置)和bind等服务，配置起来更简单，更适用于虚拟化和大数据环境的部署。
dhcp服务
其中一些关键的配置如下,配置文件/etc/dnsmasq.conf 中的注释已经给出了非常详细的解释。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | # 服务监听的网络接口地址 # If you want dnsmasq to listen for DHCP and DNS requests only on # specified interfaces (and the loopback) give the name of the # interface (eg eth0) here. # Repeat the line for more than one interface. #interface= # Or you can specify which interface _not_ to listen on #except-interface= # Or which to listen on by address (remember to include 127.0.0.1 if # you use this.) listen-address=192.168.1.132,127.0.0.1 # dhcp动态分配的地址范围 # Uncomment this to enable the integrated DHCP server, you need # to supply the range of addresses available for lease and optionally a lease time dhcp-range=192.168.1.50,192.168.1.150,48h # dhcp服务的静态绑定 # Always set the name and ipaddr of the host with hardware address # dhcp-host=00:0C:29:5E:F2:6F,192.168.1.201 # dhcp-host=00:0C:29:5E:F2:6F,192.168.1.201,infinite 无限租期 dhcp-host=00:0C:29:5E:F2:6F,192.168.1.201,os02 dhcp-host=00:0C:29:15:63:CF,192.168.1.202,os03 # 设置默认租期 # Set the limit on DHCP leases, the default is 150 #dhcp-lease-max=150 # 租期保存在下面文件 # The DHCP server needs somewhere on disk to keep its lease database. # This defaults to a sane location, but if you want to change it, use # the line below. #dhcp-leasefile=/var/lib/dnsmasq/dnsmasq.leases # 通过/etc/hosts来分配对应的hostname # Enable the address given for "judge" in /etc/hosts # to be given to a machine presenting the name "judge" when # it asks for a DHCP lease. #dhcp-host=judge # 忽略下面MAC地址的DHCP请求 # Never offer DHCP service to a machine whose ethernet # address is 11:22:33:44:55:66 #dhcp-host=11:22:33:44:55:66,ignore # dhcp所在的domain # Set the domain for dnsmasq. this is optional, but if it is set, it # does the following things. # 1) Allows DHCP hosts to have fully qualified domain names, as long # as the domain part matches this setting. # 2) Sets the "domain" DHCP option thereby potentially setting the # domain of all systems configured by DHCP # 3) Provides the domain part for "expand-hosts" domain=debugo.com # 设置默认路由出口 # dhcp-option遵循RFC 2132（Options and BOOTP Vendor Extensions),可以通过dnsmasq --help dhcp来查看具体的配置 # 很多高级的配置，如iSCSI连接配置等同样可以由RFC 2132定义的dhcp-option中给出。 # option 3为default route # Override the default route supplied by dnsmasq, which assumes the # router is the same machine as the one running dnsmasq. dhcp-option=3,192.168.0.1 # 设置NTP Server.这是使用option name而非选项名来进行设置 # Set the NTP time server addresses to 192.168.0.4 and 10.10.0.5 #dhcp-option=option:ntp-server,192.168.0.4,10.10.0.5 |
注意:当为某一MAC地址同时静态分配主机名和IP时，如果写到两条dhcp-host选项里（如下所示），则只会生效后面的一条。正确的选项写法如上配置。
1 2 | dhcp-host=00:0C:29:5E:F2:6F,192.168.1.201 dhcp-host=00:0C:29:5E:F2:6F,os02 |
重新启动客户端网卡。由于之前测试中客户端网卡已经申请了DHCP租期。所以这里需要修改租期文件，让客户端重新获得IP和hostname。
1 2 3 | [root@server] vim /var/lib/dnsmasq/dnsmasq.leases 1400240493 00:0c:29:5e:f2:6f 192.168.1.143 os02 * 1400240498 00:0c:29:15:63:cf 192.168.1.52 os01 * |
启动dnsmasq服务（server的IP为192.168.1.132）
1 | [root@server]dnsmasq |
下面在客户端进行测试：
# 确保网络接口配置使用dhcp方式
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | [root@localhost] cat /etc/sysconfig/network-scripts/ifcfg-eth1 DEVICE="eth1" BOOTPROTO=dhcp IPV6INIT=no NM_CONTROLLED=no ONBOOT="yes" TYPE="Ethernet" # 重启网络服务 [root@localhost] service network restart Shutting down interface eth0: [ OK ] Shutting down loopback interface: [ OK ] Bringing up loopback interface: [ OK ] Bringing up interface eth0: Determining IP information for eth1... done. # 检查IP地址 [ OK ] [root@os03] ifconfig eth1 Link encap:Ethernet HWaddr 00:0C:29:15:63:D9 inet addr:192.168.1.202 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe15:63d9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:251 errors:0 dropped:0 overruns:0 frame:0 TX packets:43 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:36077 (35.2 KiB) TX bytes:4598 (4.4 KiB) ...... # 检查默认路由 [root@os03] route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth1 |
配置DNS服务
dnsmasq能够缓存外部DNS记录，同时提供本地DNS解析或者作为外部DNS的代理，即dnsmasq会首先查找/etc/hosts等本地解析文件，然后再查找/etc/resolv.conf等外部nameserver配置文件中定义的外部DNS。所以说dnsmasq是一个很不错的DNS中继。DNS配置同样写入dnsmasq.conf配置文件里。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | #
本地解析文件 #
If you don't want dnsmasq to read /etc/hosts, uncomment the following line. #no-hosts #
or if you want it to read another file, as well as /etc/hosts, use this. #addn-hosts=/etc/banner_add_hosts #
Set this (and domain: see below) if you want to have a domain #
automatically added to simple names in a hosts-file. #
例如，/etc/hosts中的os01将扩展成os01.debugo.com expand-hosts #
Add local-only domains here, queries in these domains are answered #
from /etc/hosts or DHCP only. local=/debugo.com/ #
强制使用完整的解析名 #
Never forward plain names (without a dot or domain part) domain-needed #
添加额外的上级DNS主机（nameserver）配置文件 #
Change this line if you want dns to get its upstream servers from #
somewhere other that /etc/resolv.conf #resolv-file= #
不使用上级DNS主机配置文件(/etc/resolv.conf和resolv-file） #
If you don't want dnsmasq to read /etc/resolv.conf or any other #
file, getting its servers from this file instead (see below), then #
uncomment this. no-resolv #
相应的，可以为特定的域名指定解析它的nameserver。一般是其他的内部DNS name server #
Add other name servers here, with domain specs if they are for #
non-public domains. #
server=/myserver.com/192.168.0.1 #
设置DNS缓存大小（单位：DNS解析条数） #Set
the size of dnsmasq's cache. The default is 150 names. Setting the cache size to zero disables caching. cache-size=500 #
关于log的几个选项 #
For debugging purposes, log each DNS query as it passes through #
dnsmasq. log-queries #
Log lots of extra information about DHCP transactions. #log-dhcp #
Log to this syslog facility or file. (defaults to DAEMON) log-facility=/var/log/dnsmasq.log #
异步log，缓解阻塞，提高性能。 #
Enable asynchronous logging and optionally set the limit on the number of lines which will be queued by dnsmasq #
when writing to the syslog is slow. #
Dnsmasq can log asynchronously: this allows it to continue functioning without being blocked by syslog,
#
and allows syslog to use dnsmasq for DNS queries without risking deadlock. If the queue of log-lines becomes
#
full, dnsmasq will log the overflow, and the number of messages lost. #
The default queue length is 5, a sane value would be 5-25, and a maximum limit of 100 is imposed. log-async=20 #
指定domain的IP地址 #
Add domains which you want to force to an IP address here. #
The example below send any host in doubleclick.net to a local #
webserver. address=/doubleclick.net/127.0.0.1 address=/.phobos.apple.com/202.175.5.114 |
配置完成后重启dnsmasq，然后在客户端测试：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | [root@os03]nslookup
os01.debugo.com Server:192.168.1.132 Address:192.168.1.132#53 Name:os01.debugo.com Address:192.168.1.132 [root@os03]nslookup
os02.debugo.com Server:192.168.1.132 Address:192.168.1.132#53 Name:os02.debugo.com Address:192.168.1.201 [root@os03]nslookup
doubleclick.net Server:192.168.1.132 Address:192.168.1.132#53 Name:doubleclick.net Address:127.0.0.1 #注意，由于address选项解析为127.0.0.1，而非server的192.168.1.132地址。 [root@os03]nslookup
a1.phobos.apple.com Server:192.168.1.132 Address:192.168.1.132#53 Name:a1.phobos.apple.com Address:202.175.5.114 |
^^