Difference between revisions of "Dnsmasq (简体中文)"

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  # chattr +i /etc/resolv.conf
 
  # chattr +i /etc/resolv.conf
  
===== More than three nameservers =====
+
===== 三个以上域名服务器 =====
  
A limitation in the way Linux handles DNS queries is that there can only be a maximum of three nameservers used in {{ic|resolv.conf}}. As a workaround, you can make localhost the only nameserver in {{ic|resolv.conf}}, and then create a separate {{ic|resolv-file}} for your external nameservers. First, create a new resolv file for dnsmasq:
+
Linux 处理 DNS 请求时有个限制,在 {{ic|resolv.conf}} 中最多只能配置三个域名服务器(nameserver)。As a workaround, you can make localhost the only nameserver in {{ic|resolv.conf}}, and then create a separate {{ic|resolv-file}} for your external nameservers. First, create a new resolv file for dnsmasq:
  
 
{{hc|/etc/resolv.dnsmasq.conf|
 
{{hc|/etc/resolv.dnsmasq.conf|

Revision as of 12:38, 31 May 2015

翻译状态: 本文是英文页面 Dnsmasq翻译,最后翻译时间:2015-05-31,点击这里可以查看翻译后英文页面的改动。

Dnsmasq 提供 DNS 缓存和 DHCP 服务功能。作为域名解析服务器(DNS),dnsmasq可以通过缓存 DNS 请求来提高对访问过的网址的连接速度。作为DHCP 服务器,dnsmasq 可以用于为局域网电脑分配内网ip地址和提供路由。DNS和DHCP两个功能可以同时或分别单独实现。dnsmasq轻量且易配置,适用于个人用户或少于50台主机的网络。此外它还自带了一个 PXE 服务器。

安装

官方仓库安装 dnsmasq

DNS 缓存设置

要在单台电脑上以守护进程方式启动dnsmasq做DNS缓存服务器,编辑/etc/dnsmasq.conf,添加监听地址:

listen-address=127.0.0.1

如果用此主机为局域网提供默认 DNS,请用为该主机绑定固定 IP 地址,设置:

listen-address=192.168.x.x

这种情况建议配置静态IP。

DNS 地址文件

Merge-arrows-2.pngThis article or section is a candidate for merging with resolv.conf.Merge-arrows-2.png

Notes: 主题相同。本文或本节候选与resolv.conf合并。此处绝大部分功能可以在原生的/etc/resolvconf.conf文件中通过配置name_serversname_servers_append选项实现。 (Discuss in Talk:Dnsmasq (简体中文)#)

在配置好dnsmasq后,你需要编辑/etc/resolv.conf让DHCP客户端首先将本地地址(localhost)加入 DNS 文件(/etc/resolv.conf),然后再通过其他DNS服务器解析地址。配置好DHCP客户端后需要重新启动网络来使设置生效。

resolv.conf

One option is a pure resolv.conf configuration. To do this, just make the first nameserver in /etc/resolv.conf point to localhost:

/etc/resolv.conf
nameserver 127.0.0.1
# External nameservers
...

Now DNS queries will be resolved first with dnsmasq, only checking external servers if dnsmasq cannot resolve the query. dhcpcd, unfortunately, tends to overwrite /etc/resolv.conf by default, so if you use DHCP it is a good idea to protect /etc/resolv.conf. To do this, append nohook resolv.conf to the dhcpcd config file:

/etc/dhcpcd.conf
...
nohook resolv.conf

It is also possible to write protect your resolv.conf:

# chattr +i /etc/resolv.conf
三个以上域名服务器

Linux 处理 DNS 请求时有个限制,在 resolv.conf 中最多只能配置三个域名服务器(nameserver)。As a workaround, you can make localhost the only nameserver in resolv.conf, and then create a separate resolv-file for your external nameservers. First, create a new resolv file for dnsmasq:

/etc/resolv.dnsmasq.conf
# Google's nameservers, for example
nameserver 8.8.8.8
nameserver 8.8.4.4

And then edit /etc/dnsmasq.conf to use your new resolv file:

/etc/dnsmasq.conf
...
resolv-file=/etc/resolv.dnsmasq.conf
...

使用dhcpcd

dhcpcd 可以是通过创建(或编辑)/etc/resolv.conf.head文件或 /etc/resolv.conf.tail文件来指定dns服务器,使/etc/resolv.conf不会被每次都被dhcpcd重写

echo "nameserver 127.0.0.1" > /etc/resolv.conf.head #设置dns服务器为127.0.0.1

使用dhclient

要使用 dhclient, 取消 /etc/dhclient.conf 文件中如下行的注释:

prepend domain-name-servers 127.0.0.1;

使用NetworkManager

Networkmanager 可以靠自身配置文件的设置项启动 dnsmasq 。在 NetworkManager.conf 文件的 [main] 节段添加 dns=dnsmasq 配置语句,然后禁用由 systemd 启动的 dnsmasq.service:

/etc/NetworkManager/NetworkManager.conf
[main]
plugins=keyfile
dns=dnsmasq

可以在 /etc/NetworkManager/dnsmasq.d/ 目录下为 dnsmasq 创建自定义配置文件。例如,调整 DNS 缓存大小(保存在内存中):

/etc/NetworkManager/dnsmasq.d/cache
cache-size=1000

dnsmasqNetworkManager 启动后,此目录下配置文件中的配置将取代默认配置。

Tip: This method can allow you to enable custom DNS settings on particular domains. For instance: server=/example1.com/exemple2.com/xx.xxx.xxx.x change the first DNS address to xx.xxx.xxx.xx while browsing only the following websites example1.com, example2.com. This method is preferred to a global DNS configuration when using particular DNS nameservers which lack of speed, stability, privacy and security.

IPv6

Enabling dnsmasq in NetworkManager may break IPv6-only DNS lookups (i.e. dig -6 [hostname]) which would otherwise work. In order to resolve this, creating the following file will configure dnsmasq to also listen to the IPv6 loopback:

/etc/NetworkManager/dnsmasq.d/ipv6_listen.conf
listen-address=::1

In addition, dnsmasq also does not prioritize upstream IPv6 DNS. Unfortunately NetworkManager does not do this (Ubuntu Bug). A workaround would be to disable IPv4 DNS in the NetworkManager config, assuming one exists

其他方式

Another option is in NetworkManagers' settings (usually by right-clicking the applet) and entering settings manually. Setting up will depending on the type of front-end used; the process usually involves right-clicking on the applet, editing (or creating) a profile, and then choosing DHCP type as 'Automatic (specify addresses).' The DNS addresses will need to be entered and are usually in this form: 127.0.0.1, DNS-server-one, ....

DHCP 服务器设置

dnsmasq默认关闭DHCP功能,如果该主机需要为局域网中的其他设备提供IP和路由,应该对dnsmasq 配置文件(/etc/dnsmasq.conf)必要的配置如下:

# Only listen to routers' LAN NIC.  Doing so opens up tcp/udp port 53 to
# localhost and udp port 67 to world:
interface=<LAN-NIC>

# dnsmasq will open tcp/udp port 53 and udp port 67 to world to help with
# dynamic interfaces (assigning dynamic ips). Dnsmasq will discard world
# requests to them, but the paranoid might like to close them and let the 
# kernel handle them:
bind-interfaces

# Dynamic range of IPs to make available to LAN pc
dhcp-range=192.168.111.50,192.168.111.100,12h

# If you’d like to have dnsmasq assign static IPs, bind the LAN computer's
# NIC MAC address:
dhcp-host=aa:bb:cc:dd:ee:ff,192.168.111.50

启动守护进程

现在我们启动它:

# systemctl start dnsmasq

要让dnsmasq开机启动:

# systemctl enable dnsmasq

查看dnsmasq是否启动正常,检查 /var/log/messages.log 日志文件。

你需要重启 network 这样 dhcpd 会重新建立 /etc/resolv.conf

# /etc/rc.d/network restart

现在让我们测试一下 DNS 查询然后测量响应时间:

$ dig archlinux.org | grep "Query time"

Query time 应该会减少。

并且如果你移除 grep,你可以看到使用的服务器(Query time 下一行),现在它应该是 localhost 也就是 127.0.0.1。

测试

DNS 缓存

要测试查询速度,请访问一个 dnsmasq 启动后没有访问过的网站,执行 (dig (位于 dnsutils 软件包):

$ dig archlinux.org | grep "Query time"

再次运行命令,因为使用了缓存,查询时间应该大大缩短。

DHCP 服务器

从一个连接到使用了 dnsmasq 的计算机的计算机,配置它使用 DHCP 自动获取 IP 地址,然后尝试连接到你平时使用的网络。

小技巧

避免 OpenDNS 重定向 Google 请求

要避免 OpenDNS 重定向所有 Google 请求到他们自己的搜索服务器,添加以下内容到 /etc/dnsmasq.conf

server=/www.google.com/X.X.X.X

用你的 ISP 的 DNS 服务器/路由器的 IP 替代 X.X.X.X 。

查看租约

cat /var/lib/misc/dnsmasq.leases

添加自定义域

It is possible to add a custom domain to hosts in your (local) network:

local=/home.lan/
domain=home.lan

In this example it is possible to ping a host/device (e.g. defined in your hosts file) as hostname.home.lan.

Uncomment expand-hosts to add the custom domain to hosts entries:

expand-hosts

Without this setting, you'll have to add the domain to entries of /etc/hosts.