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.
- 1 Installation
- 2 Configuration
- 3 DNS cache setup
- 4 DHCP server setup
- 5 TFTP server setup
- 6 PXE setup
- 7 Start the daemon
- 8 Tips and tricks
- 9 See also
To configure dnsmasq, you need to edit
/etc/dnsmasq.conf. The file contains extensive comments explaining its options.
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:
To use this computer to listen on its 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.
Multiple ip address settings:
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.
One option is a pure
resolv.conf configuration. To do this, just make the first nameserver in
/etc/resolv.conf point to localhost:
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.
/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:
... nohook resolv.conf
It is also possible to write protect your resolv.conf:
# chattr +i /etc/resolv.conf
More than three nameservers
A limitation in 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:
# Google's nameservers, for example nameserver 220.127.116.11 nameserver 18.104.22.168
And then edit
/etc/dnsmasq.conf to use your new resolv file:
... resolv-file=/etc/resolv.dnsmasq.conf ...
dhcpcd has the ability to prepend or append nameservers to
/etc/resolv.conf by creating (or editing) the
/etc/resolv.conf.tail files respectively:
echo "nameserver 127.0.0.1" > /etc/resolv.conf.head
prepend domain-name-servers 127.0.0.1;
DNS requests can be sped up by caching previous requests locally for subsequent lookup. NetworkManager has a plugin to enable DNS caching using dnsmasq, but it is not enabled in the default configuration.
/etc/NetworkManager/NetworkManager.conf and change the
dns in the
[main] ... dns=dnsmasq
Now restart NetworkManager or reboot. NetworkManager will automatically start dnsmasq and add 127.0.0.1 to
/etc/resolv.conf. The actual DNS servers can be found in
/run/NetworkManager/dnsmasq.conf. You can verify dnsmasq is being used by doing the same DNS lookup twice with
$ dig example.com that can be installed with and verifying the server and query times.
Usage with libvirt
Network-manager think if there is one running libvirt that he run this before. To fix conflicts between other dnsmasq, eg: used in libvirt, you must run it externally.
We do not want change our resolv.conf automaticly.
[main] ... dns=none
We put it manually here.
The interface to bind and bind it even if there is second dnsmasq runned on computer.
This start service if interface is up. This service can start only once before stop which will be initiate by systemd on restart/shutdown.
#!/bin/sh if [ -n "$2" ] && [ "$2" = "up" ]; then # $INTERFACE is up systemctl start NetworkManager-dnsmasq.service fi
[Unit] Description=A lightweight DHCP and caching DNS server After=network.target Documentation=man:dnsmasq(8) [Service] Type=dbus BusName=uk.org.thekelleys.dnsmasq ExecStartPre=/usr/bin/dnsmasq --test ExecStart=/usr/bin/dnsmasq -k --enable-dbus --user=dnsmasq --pid-file --conf-dir=/etc/NetworkManager/dnsmasq.d/ ExecReload=/bin/kill -HUP $MAINPID
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):
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:
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
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, ....
To do a lookup speed test choose a website that has not been visited since dnsmasq has been started (dig is part of thepackage):
$ 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 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
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.
TFTP server setup
Create a directory for TFTP root (e.g.
/srv/tftp) to put transferable files in.
To use dnsmasq's TFTP secure mode chown TFTP root and all files in it to
Enable TFTP in
enable-tftp tftp-root=/srv/tftp tftp-secure
PXE requires DHCP and TFTP servers, both functions can be provided by dnsmasq.
- set up TFTP server and DHCP server
- copy and configure a PXE compatible bootloader (e.g. PXELINUX) on TFTP root
- enable PXE in
To simply send one file:
To send a file depending on client architecture:
pxe-service=x86PC, "PXELINUX (BIOS)", "bios/lpxelinux" pxe-service=X86-64_EFI, "PXELINUX (EFI)", "efi64/syslinux.efi"
dhcp-match=set:efi-x86_64,option:client-arch,7 dhcp-match=set:efi-x86_64,option:client-arch,9 dhcp-match=set:efi-x86,option:client-arch,6 dhcp-match=set:bios,option:client-arch,0 dhcp-boot=tag:efi-x86_64,"efi64/syslinux.efi" dhcp-boot=tag:efi-x86,"efi32/syslinux.efi" dhcp-boot=tag:bios,"bios/lpxelinux.0"
The rest is up to the bootloader.
Start the daemon
To see if dnsmasq started properly, check the system's journal:
$ journalctl -u dnsmasq
The network will also need to be restarted so the DHCP client can create a new
Tips and tricks
Prevent OpenDNS redirecting Google queries
To prevent OpenDNS from redirecting all Google queries to their own search server, add to
server=/www.google.com/<ISP DNS IP>
$ cat /var/lib/misc/dnsmasq.leases
Adding a custom domain
It is possible to add a custom domain to hosts in your (local) network:
In this example it is possible to ping a host/device (e.g. defined in your hosts file) as
expand-hosts to add the custom domain to hosts entries:
Without this setting, you'll have to add the domain to entries of /etc/hosts.
In some cases, such as when operating a captive portal, it can be useful to resolve specific domains names to a hard-coded set of addresses. This is done with the
Furthermore, it's possible to return a specific address for all domain names that are not answered from
/etc/hosts or DHCP by using a special wildcard:
More than one instance
If we want two or more dnsmasq servers works per interface(s).
To do this staticly, server per interface, use
bind-interface options. This enforce start second dnsmasq.
In this case we can exclude per interface and bind any others: