DNSmasq – 配置DNS和DHCP

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。

# 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。

[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

[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。

#
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：

[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

来源： http://blog.csdn.net/nosodeep/article/details/45971705

来自为知笔记(Wiz)