Difference between revisions of "Dnsmasq"

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(DNS cache setup: rename heading to #Caching DNS server)
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The network will also need to be restarted so the DHCP client can create a new {{ic|/etc/resolv.conf}}.
 
The network will also need to be restarted so the DHCP client can create a new {{ic|/etc/resolv.conf}}.
  
== Caching DNS server ==
+
== Server setup ==
 +
 
 +
=== Caching DNS server ===
  
 
To set up dnsmasq as a DNS caching daemon on a single computer edit {{ic|/etc/dnsmasq.conf}} and uncomment the {{ic|listen-address}} directive, adding in the localhost IP address:
 
To set up dnsmasq as a DNS caching daemon on a single computer edit {{ic|/etc/dnsmasq.conf}} and uncomment the {{ic|listen-address}} directive, adding in the localhost IP address:
Line 73: Line 75:
 
See {{man|8|dnsmasq}} for more options you might want to use.
 
See {{man|8|dnsmasq}} for more options you might want to use.
  
=== DNS addresses file ===
+
==== DNS addresses file ====
  
 
{{Merge|resolv.conf|Same topic. Also note that most of this can also be done natively in {{ic|/etc/resolvconf.conf}} using the {{ic|name_servers}} and {{ic|name_servers_append}} options.}}
 
{{Merge|resolv.conf|Same topic. Also note that most of this can also be done natively in {{ic|/etc/resolvconf.conf}} using the {{ic|name_servers}} and {{ic|name_servers_append}} options.}}
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After configuring dnsmasq, the DHCP client will need to prepend the localhost address to the known DNS addresses in {{ic|/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.
 
After configuring dnsmasq, the DHCP client will need to prepend the localhost address to the known DNS addresses in {{ic|/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.
  
==== openresolv ====
+
===== openresolv =====
  
 
If your network manager supports [[openresolv]], instead of directly altering {{ic|/etc/resolv.conf}}, you can use ''openresolv'' to generate configuration files for dnsmasq. [https://roy.marples.name/projects/openresolv/config]
 
If your network manager supports [[openresolv]], instead of directly altering {{ic|/etc/resolv.conf}}, you can use ''openresolv'' to generate configuration files for dnsmasq. [https://roy.marples.name/projects/openresolv/config]
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  resolv-file=/etc/dnsmasq-resolv.conf
 
  resolv-file=/etc/dnsmasq-resolv.conf
  
==== resolv.conf ====
+
===== resolv.conf =====
  
 
One option is a pure {{ic|resolv.conf}} configuration. To do this, just make the first nameserver in {{ic|/etc/resolv.conf}} point to localhost:
 
One option is a pure {{ic|resolv.conf}} configuration. To do this, just make the first nameserver in {{ic|/etc/resolv.conf}} point to localhost:
Line 123: Line 125:
 
  # chattr +i /etc/resolv.conf
 
  # chattr +i /etc/resolv.conf
  
===== More than three nameservers =====
+
====== 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 {{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:
 
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:
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}}
 
}}
  
==== dhcpcd ====
+
===== dhcpcd =====
  
 
{{Remove|dhcpcd supports [[#openresolv]].}}
 
{{Remove|dhcpcd supports [[#openresolv]].}}
Line 149: Line 151:
 
  echo "nameserver 127.0.0.1" > /etc/resolv.conf.head
 
  echo "nameserver 127.0.0.1" > /etc/resolv.conf.head
  
==== dhclient ====
+
===== dhclient =====
  
 
For {{Pkg|dhclient}}, uncomment in {{ic|/etc/dhclient.conf}}:
 
For {{Pkg|dhclient}}, uncomment in {{ic|/etc/dhclient.conf}}:
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  prepend domain-name-servers 127.0.0.1;
 
  prepend domain-name-servers 127.0.0.1;
  
=== NetworkManager ===
+
==== NetworkManager ====
 +
 
 
{{Move|NetworkManager#Enable DNS Caching|NetworkManager configuration belongs to [[NetworkManager]].}}
 
{{Move|NetworkManager#Enable DNS Caching|NetworkManager configuration belongs to [[NetworkManager]].}}
  
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Now restart NetworkManager or reboot. NetworkManager will automatically start dnsmasq and add 127.0.0.1 to {{ic|/etc/resolv.conf}}. The actual DNS servers can be found in {{ic|/run/NetworkManager/resolv.conf}}. You can verify dnsmasq is being used by doing the same DNS lookup twice with {{ic|$ drill example.com}} and verifying the server and query times.
 
Now restart NetworkManager or reboot. NetworkManager will automatically start dnsmasq and add 127.0.0.1 to {{ic|/etc/resolv.conf}}. The actual DNS servers can be found in {{ic|/run/NetworkManager/resolv.conf}}. You can verify dnsmasq is being used by doing the same DNS lookup twice with {{ic|$ drill example.com}} and verifying the server and query times.
  
==== Custom configuration ====
+
===== Custom configuration =====
  
 
Custom configurations can be created for ''dnsmasq'' by creating configuration files in {{ic|/etc/NetworkManager/dnsmasq.d/}}. For example, to change the size of the DNS cache (which is stored in RAM):
 
Custom configurations can be created for ''dnsmasq'' by creating configuration files in {{ic|/etc/NetworkManager/dnsmasq.d/}}. For example, to change the size of the DNS cache (which is stored in RAM):
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}}
 
}}
  
==== IPv6 ====
+
===== IPv6 =====
  
 
Enabling {{ic|dnsmasq}} in NetworkManager may break IPv6-only DNS lookups (i.e. {{ic|drill -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:
 
Enabling {{ic|dnsmasq}} in NetworkManager may break IPv6-only DNS lookups (i.e. {{ic|drill -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:
Line 187: Line 190:
 
In addition, {{ic|dnsmasq}} also does not prioritize upstream IPv6 DNS. Unfortunately NetworkManager does not do this ([https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/936712 Ubuntu Bug]). A workaround would be to disable IPv4 DNS in the NetworkManager config, assuming one exists
 
In addition, {{ic|dnsmasq}} also does not prioritize upstream IPv6 DNS. Unfortunately NetworkManager does not do this ([https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/936712 Ubuntu Bug]). A workaround would be to disable IPv4 DNS in the NetworkManager config, assuming one exists
  
==== Other methods ====
+
===== 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: {{ic|127.0.0.1, DNS-server-one, ...}}.
 
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: {{ic|127.0.0.1, DNS-server-one, ...}}.
  
=== Test ===
+
==== Test ====
  
 
To do a lookup speed test choose a website that has not been visited since dnsmasq has been started (''drill'' is part of the {{Pkg|ldns}} package):
 
To do a lookup speed test choose a website that has not been visited since dnsmasq has been started (''drill'' is part of the {{Pkg|ldns}} package):
Line 206: Line 209:
 
;; Query time: 2 msec
 
;; Query time: 2 msec
 
}}
 
}}
 
== Server setup ==
 
  
 
=== DNS server ===
 
=== DNS server ===

Revision as of 12:00, 20 June 2018

dnsmasq provides a local DNS server, a DHCP server with support for DHCPv6 and PXE, and a TFTP server. It is designed to be lightweight and have a small footprint, suitable for resource constrained routers and firewalls. dnsmasq can also be configured to cache DNS queries for improved DNS lookup speeds to previously visited sites.

Installation

Install the dnsmasq package.

Configuration

Merge-arrows-2.pngThis article or section is a candidate for merging with #Server setup.Merge-arrows-2.png

Notes: dnsmasq can be configured to do many things, there is no generic configuration that would apply to all use cases. (Discuss in Talk:Dnsmasq#)

To configure dnsmasq, you need to edit /etc/dnsmasq.conf. The file contains extensive comments explaining its options. For all available options see dnsmasq(8).

Warning: dnsmasq by default enables its DNS server. If you do not require it, you need to explicitly disable it by setting DNS port to 0:
/etc/dnsmasq.conf
port=0
Tip: To check configuration file(s) syntax, execute:
$ dnsmasq --test

Start the daemon

Start/enable dnsmasq.service.

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

$ journalctl -u dnsmasq.service

The network will also need to be restarted so the DHCP client can create a new /etc/resolv.conf.

Server setup

Caching DNS server

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=::1,127.0.0.1

To use this computer to listen on its LAN IP address for other computers on the network. It is recommended that you use a static LAN IP in this case.

listen-address=192.168.1.1    # Example IP

Set the number of cached domain names with cache-size=size (the default is 150) and optionally disable caching of "no such domain" responces with no-negcache:

cache-size=1000
no-negcache

To validate DNSSEC set the option dnssec and load the DNSSEC trust anchors provided by the dnsmasq package:

dnssec
conf-file=/usr/share/dnsmasq/trust-anchors.conf

See dnsmasq(8) for more options you might want to use.

DNS addresses file

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

Notes: Same topic. Also note that most of this can also be done natively in /etc/resolvconf.conf using the name_servers and name_servers_append options. (Discuss in Talk:Dnsmasq#)

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.

openresolv

If your network manager supports openresolv, instead of directly altering /etc/resolv.conf, you can use openresolv to generate configuration files for dnsmasq. [1]

Edit /etc/resolvconf.conf and add the loopback addresses as name servers, and configure openresolv to write out dnsmasq configuration:

/etc/resolvconf.conf
# Use the local name server
name_servers="::1 127.0.0.1"

# Write out dnsmasq extended configuration and resolv files
dnsmasq_conf=/etc/dnsmasq-openresolv.conf
dnsmasq_resolv=/etc/dnsmasq-resolv.conf

Run resolvconf -u so that the configuration files get created. If the files do not exist dnsmasq.service will fail to start.

Edit dnsmasq's configuration file to use openresolv's generated configuration:

# Read configuration generated by openresolv
conf-file=/etc/dnsmasq-openresolv.conf
resolv-file=/etc/dnsmasq-resolv.conf
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 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:

/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

Tango-edit-cut.pngThis section is being considered for removal.Tango-edit-cut.png

Reason: dhcpcd supports #openresolv. (Discuss in Talk:Dnsmasq#)
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

Tango-go-next.pngThis article or section is a candidate for moving to NetworkManager#Enable DNS Caching.Tango-go-next.png

Notes: NetworkManager configuration belongs to NetworkManager. (Discuss in Talk:Dnsmasq#)
NetworkManager has a plugin to enable DNS using dnsmasq. The advantages of this setup is that DNS lookups will be cached, shortening resolve times, and DNS lookups of VPN hosts will be routed to the relevant VPN's DNS servers (especially useful if you are connected to more than one VPN).

Make sure dnsmasq has been installed, but has been disabled. Then, create /etc/NetworkManager/conf.d/dns.conf and add the following to it:

/etc/NetworkManager/conf.d/dns.conf
[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/resolv.conf. You can verify dnsmasq is being used by doing the same DNS lookup twice with $ drill example.com and verifying the server and query times.

Custom configuration

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.conf
cache-size=1000
IPv6

Enabling dnsmasq in NetworkManager may break IPv6-only DNS lookups (i.e. drill -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

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, ....

Test

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

$ drill 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:

$ drill archlinux.org | grep "Query time"
;; Query time: 18 msec
$ drill archlinux.org | grep "Query time"
;; Query time: 2 msec

DNS server

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Add instructions. (Discuss in Talk:Dnsmasq#)

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 /etc/hosts file) as hostname.home.lan.

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

expand-hosts

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

DHCP server

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Add instructions for IPv6 and router advertisement. (Discuss in Talk:Dnsmasq#)

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

# Optionally set a domain name
domain=example.com

# Set default gateway
dhcp-option=3,192.168.1.1

# Set DNS servers to announce
dhcp-option=6,8.8.8.8,8.8.4.4

# Dynamic range of IPs to make available to LAN PC and the lease time. 
# Ideally set the lease time to 5m only at first to test everything works okay before you set long-lasting records.
dhcp-range=192.168.111.50,192.168.111.100,12h

# If you’d like to have dnsmasq assign static IPs to some clients, bind the LAN computers
# NIC MAC addresses:
dhcp-host=aa:bb:cc:dd:ee:ff,192.168.111.50
dhcp-host=aa:bb:cc:ff:dd:ee,192.168.111.51

See dnsmasq(8) for more options.

Test

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.

If you inspect the /var/lib/misc/dnsmasq.leases file on the server, you should be able to see the lease.

TFTP server

dnsmasq has built-in TFTP server.

To use it, create a directory for TFTP root (e.g. /srv/tftp) to put transferable files in.

For increased security it is advised to use dnsmasq's TFTP secure mode. In secure mode only files owned by the dnsmasq user will be served over TFTP. You will need to chown TFTP root and all files in it to dnsmasq user to use this feature.

Enable TFTP in dnsmasq.conf:

/etc/dnsmasq.conf
enable-tftp
tftp-root=/srv/tftp
tftp-secure

See dnsmasq(8) for more options.

PXE server

PXE requires DHCP and TFTP servers, both functions can be provided by dnsmasq.

Tip: dnsmasq can add PXE booting options to a network with an already running DHCP server:
/etc/dnsmasq.conf
interface=enp0s0
bind-dynamic
dhcp-range=192.168.0.1,proxy
  1. set up #TFTP server and #DHCP server
  2. copy and configure a PXE compatible bootloader (e.g. PXELINUX) on TFTP root
  3. enable PXE in /etc/dnsmasq.conf:
Note:
  • file paths are relative to TFTP root
  • if the file has a .0 suffix, you must exclude the suffix in pxe-service options

To simply send one file:

dhcp-boot=lpxelinux.0

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"
Note: In case pxe-service does not work (especially for UEFI-based clients), combination of dhcp-match and dhcp-boot can be used. See RFC4578 for more client-arch numbers for use with dhcp boot protocol.
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"

See dnsmasq(8) for more options.

The rest is up to the bootloader.

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>

Override addresses

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 address config:

address=/example.com/1.2.3.4

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:

address=/#/1.2.3.4

More than one instance

If we want two or more dnsmasq servers works per interface(s).

Static

To do this staticly, server per interface, use interface and bind-interface options. This enforce start second dnsmasq.

Dynamic

In this case we can exclude per interface and bind any others:

except-interface=lo
bind-dynamic
Note: This is default in libvirt.

See also