# dnsmasq

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 speeds to previously visited sites, and 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. It also comes with a PXE server.

## Installation

Install dnsmasq from the official repositories.

## DNS Cache Setup

To set up dnsmasq as a DNS caching daemon on a single computer edit `/etc/dnsmasq.conf` and uncomment the `listen-address` directive, adding in the localhost IP address:

    listen-address=127.0.0.1

To use this computer to listen on it's LAN IP address for other computers on the network:

    listen-address=192.168.1.1    # Example IP

It is recommended that you use a static LAN ip in this case.

### DNS Addresses File

After configuring dnsmasq the DHCP client will need to prepend the localhost address to the known DNS addresses in `/etc/resolv.conf`. This causes all queries to be sent to dnsmasq before trying to resolve them with an external DNS. After the DHCP client is configured the network will need to be restarted for changes to take effect.

#### 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

##### More than three nameservers

A limitation the way Linux handles DNS queries is that there can only be a maximum of three nameservers used in `resolv.conf`. 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
    ...

#### 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

NetworkManager has the ability to start dnsmasq from its configuration file. Add the option `dns=dnsmasq` to `NetworkManager.conf` in the `[main]` section then disable the `dnsmasq.service` from being loaded by systemd:

    /etc/NetworkManager/NetworkManager.conf

    [main]
    plugins=keyfile
    dns=dnsmasq

Custom configurations can be created for dnsmasq by creating configuration files in `/etc/NetworkManager/dnsmasq.d/`. For example, to change the size of the DNS cache (which is stored in RAM):

    /etc/NetworkManager/dnsmasq.d/cache

    cache-size=1000

When dnsmasq is started by `NetworkManager`, the config file in this directory is used instead of the default config file.

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.

##### Other methods

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 server setup

By default dnsmasq has the DHCP functionality turned off, if you want to use it you must turn it on in (`/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

## Start the daemon

To have dnsmasq to load upon startup:

    # systemctl enable dnsmasq

To start dnsmasq immediately:

    # systemctl start dnsmasq

To see if dnsmasq started properly, check the system's journal:

    $ journalctl -u dnsmasq

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:

    # dig archlinux.org | grep "Query time" ;; Query time: 18 msec
    # dig archlinux.org | grep "Query time" ;; Query time: 2 msec

### 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 and tricks

### 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

### Adding a custom domain

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.

Category:

- Domain Name System