Difference between revisions of "Dnsmasq"

From ArchWiki
Jump to: navigation, search
(Change category to Domain Name System.)
m (NetworkManager)
Line 70: Line 70:
  
 
if [[ ! $(grep 127.0.0.1 /etc/resolv.conf) ]]; then
 
if [[ ! $(grep 127.0.0.1 /etc/resolv.conf) ]]; then
   sed -i ’1s|^|nameserver 127.0.0.1\n|/etc/resolv.conf
+
   sed -i `1s|^|nameserver 127.0.0.1\n|` /etc/resolv.conf
 
fi</nowiki>}}
 
fi</nowiki>}}
  

Revision as of 20:08, 13 August 2012

dnsmasq provides services as a DNS cacher and a DHCP server. As a Domain Name Server (DNS), it can cache DNS queries to improve connection speed to previously visited sites. As a DHCP server, dnsmasq can be used to provide internal IP addresses and routes to computers on a LAN. Either or both of these services can be implemented. dnsmasq is considered to be lightweight and easy to configure; it is designed for personal computer use or for use on a network with less than 50 computers.

Installing

Install dnsmasq from the official repositories.

DHCP Server Setup

The dnsmasq configuration file needs to be configured (/etc/dnsmasq.conf). Here are the important settings:

# 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

DNS Cache Setup

To set up dnsmasq as a DNS caching daemon on a single computer edit /etc/dnsmasq.conf and uncomment the localhost listening address:

listen-address=127.0.0.1

To use this computer to act as a default DNS specify the fixed IP address of the network:

listen-address=<192.168.1.1>  # Example IP

DHCP Setup

After configuring dnsmasq, the DHCP client will need to prepend the localhost address to the known DNS addresses file (/etc/resolv.conf) - this sends all queries to dnsmasq before trying to resolve them to an external DNS. After the DHCP client is configured the network will need to be restarted for changes to take effect.

dhcpcd

dhcpcd has the ability to prepend or append nameservers to /etc/resolv.conf by creating (or editing) the /etc/resolv.conf.head and /etc/resolv.conf.tail files respectively:

echo "nameserver 127.0.0.1" > /etc/resolv.conf.head

dhclient

For dhclient, uncomment in /etc/dhclient.conf:

prepend domain-name-servers 127.0.0.1;

NetworkManager

Since the upgrade of NetworkManager to 0.7, Arch Linux now calls dhcpcd directly instead of the common default with dhclient. Because of the arguments set with dhcpcd, it no longer sources the /etc/resolv.conf.head, and /etc/resolv.conf.tail settings for insertion of name servers. Several options are available.

The first option would be to add a script to the NetworkManager dispatcher to prepend localhost to resolv.conf:

/etc/NetworkManager/dispatcher.d/localhost-prepend
#!/bin/bash                                       
# Prepend localhost to resolv.conf for dnsmasq

if [[ ! $(grep 127.0.0.1 /etc/resolv.conf) ]]; then
  sed -i `1s|^|nameserver 127.0.0.1\n|` /etc/resolv.conf
fi

and make it executable:

# chmod +x /etc/NetworkManager/dispatcher.d/localhost-prepend

The second option be to go into 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, ....

Lastly, NetworkManager with dhclient can be used (networkmanager-dhclientAUR).

Start the Daemon

To have dnsmasq to load upon startup, add it to the daemons array in /etc/rc.conf:

DAEMONS=(... dnsmasq network ...)

To stand dnsmasq immediately:

$ rc.d start dnsmasq

To see if dnsmasq started properly, check the log; dnsmasq sends its messages to /var/log/messages.log. The network will also need to be restarted so the the DHCP client can create a new /etc/resolv.conf.

Test

DNS Caching

To do a lookup speed test choose a website that has not been visited since dnsmasq has been started (dig is part of the dnsutils package):

$ dig archlinux.org | grep "Query time"

Running the command again will use the cached DNS IP and result in a faster lookup time if dnsmasq is setup correctly.

DHCP Server

From a computer that is connected to the one with dnsmasq on it, configure it to use DHCP for automatic IP address assignment, then attempt to log into the network normally.

Tips

Prevent OpenDNS Redirecting Google Queries

To prevent OpenDNS from redirecting all Google queries to their own search server, add to /etc/dnsmasq.conf:

server=/www.google.com/<ISP DNS IP>

View leases

cat /var/lib/misc/dnsmasq.leases