Difference between revisions of "Unbound"

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(Everyone should know how to install with pacman, and it's just silly to only show how to install the dependency anyway.)
(Roothints systemd timer: This would restart unbound before the download completes. Besides, services should not restart each other.)
 
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[[Category:Domain Name System]]
 
[[Category:Domain Name System]]
Unbound is a validating, recursive, and caching DNS resolver.
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[[ja:Unbound]]
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[[zh-cn:Unbound]]
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{{Related articles start}}
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{{Related|DNSSEC}}
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{{Related|BIND}}
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{{Related|DNSCrypt}}
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{{Related|dnsmasq}}
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{{Related|Pdnsd}}
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{{Related articles end}}
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[https://unbound.net/ Unbound] is a validating, recursive, and caching DNS resolver. According to [[Wikipedia:Unbound (DNS Server)]], "Unbound has supplanted the Berkeley Internet Name Domain ([[BIND]]) as the default, base-system name server in several open source projects, where it is perceived as smaller, more modern, and more secure for most applications."
  
==Installation==
+
== Installation ==
  
Install {{Pkg|unbound}}, and {{Pkg|expat}} which is dependency for [[DNSSEC]]:
+
[[Install]] the {{Pkg|unbound}} package.
  
==Pre-configuration==
+
Additionally, the {{Pkg|expat}} package is required for [[DNSSEC]] validation.
  
For querying a host that is not cached as an address the resolver needs to start at the top of the server tree and query the root servers to know where to go for the top level domain for the address being queried.  Therefore it is necessary to put a "root hints" file into the unbound config directory. The simplest way to do this is to run the command:
+
== Configuration ==
  
{{ic|wget ftp://FTP.INTERNIC.NET/domain/named.cache -O /etc/unbound/root.hints}}
+
A default configuration is already included at{{ic|/etc/unbound/unbound.conf}}. Additionally, there is a commented sample configuration file with other available options located at {{ic|/etc/unbound/unbound.conf.example}}. The following sections highlight different settings for the configuration file. See {{ic|man unbound.conf}} for other settings and more details.
  
It is a good idea to run this every six months or so in order to make sure the list of root servers is up to date. This can be done manually or by setting up a cron job for the task.
+
Unless otherwise specified, any options listed in this section are to be placed under the {{ic|server}} section in the configuration like so:
  
If you are going to use DNSSEC then you will need the root server trust key anchor in the file root.key which you can place in a directory owned by user unbound.  
+
{{hc|/etc/unbound/unbound.conf|
 +
server:
 +
  ...
 +
  ''setting'': ''value''
 +
  ...
 +
}}
  
mkdir /etc/unbound/keys
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=== Access control ===
chown unbound:unbound /etc/unbound/keys
+
  
Then create the file root.key and place it in this directory [/etc/unbound/keys/] and make sure the file root.key is owned by user unbound as below.
+
You can specify the interfaces to answer queries from by IP address. To listen on ''localhost'', use the default setting:
  
The line below is the 2010 trust anchor for the root zone, and this line is the only line in the file root.key. You can independently verify the root zone anchor by going to the IANA.org Index of /root-anchors.
+
interface: 127.0.0.1
  
. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5
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To listen on all interfaces, use the following:
  
Once the file is created make unbound the owner:
+
interface: 0.0.0.0
  
{{ic|# chown unbound:unbound /etc/unbound/keys/root.key}}
+
To control which systems can access the server by IP address, use the {{ic|access-control}} option:
  
 +
access-control: ''subnet'' ''action''
  
If you will want logging for unbound then create a log file which can also be in the same directory, but you can choose any location. One way is then to do as root:
+
For example:
  
  # touch /etc/unbound/unbound.log
+
  access-control: 192.168.1.0/24 allow
# chown unbound:unbound /etc/unbound/unbound.log
+
  
Then you can include the logging parameter when you set up the main unbound.conf file as below.
+
''action'' can be one of {{ic|deny}} (drop message), {{ic|refuse}} (polite error reply), {{ic|allow}} (recursive ok), or {{ic|allow_snoop}} (recursive and nonrecursive ok). By default everything is refused except for localhost.
  
==Basic configuration==
+
=== Root hints ===
  
===Unbound configuration===
+
For querying a host that is not cached as an address the resolver needs to start at the top of the server tree and query the root servers to know where to go for the top level domain for the address being queried. Unbound comes with default builtin hints, but it is good practice to use a root-hints file since the builtin hints may become outdated.
  
Unbound is easy to configure. In the directory /etc/unbound/ there is a sample config file [unbound.conf.example] which can be copied to /etc/unbound/unbound.conf and with the adjustments to the file for your own needs it is enough to run on both IPv4 and IPv6 without access restrictions. Once copied to unbound.conf and then uncomment lines or add in lines as needed.
+
First point ''unbound'' to the {{ic|root.hints}} file:
  
For the case where you want the unbound server to listen to requests from the machine that it is running on then make sure that the line defining which address it is going to listen on is included:
+
root-hints: "/etc/unbound/root.hints"
  
interface: 127.0.0.1
+
Then, put a ''root hints'' file into the ''unbound'' configuration directory. The simplest way to do this is to run the command:
  
It is also important to include a line to point to the root.hints file that was prepared before editing the unbound.conf file:
+
{{bc|<nowiki># curl -o /etc/unbound/root.hints https://www.internic.net/domain/named.cache</nowiki>}}
  
root-hints: "/etc/unbound/root.hints"
+
It is a good idea to update {{ic|root.hints}} every six months or so in order to make sure the list of root servers is up to date. This can be done manually or by using [[Systemd/Timers]]. See [[#Roothints systemd timer]] for an example.
 +
 
 +
=== Local DNS server ===
 +
 
 +
If you want to use ''unbound'' as your local DNS server, set your nameserver to {{ic|127.0.0.1}} in your [[resolv.conf]]. You will want to have your nameserver be [[Resolv.conf#Preserve_DNS_settings|preserved]].
 +
 
 +
{{Tip|1=A simple way to do this is to install the {{pkg|openresolv}} package and uncomment the line containing {{ic|1=name_servers=127.0.0.1}} in {{ic|/etc/resolvconf.conf}}. Then run {{ic|resolvconf -u}} to generate {{ic|/etc/resolv.conf}}.}}
 +
 
 +
See [[Resolv.conf#Testing]] on how to test your settings.
 +
 
 +
Check specifically that the server being used is {{ic|127.0.0.1}} after making permanent changes to [[resolv.conf]].
 +
 
 +
=== DNSSEC validation ===
 +
 
 +
''unbound'' automatically copies the root server trust key anchor file from {{ic|/etc/trusted-key.key}} to {{ic|/etc/unbound/trusted-key.key}}. To use DNSSEC validation, point ''unbound'' to this file by adding the following setting:
 +
 
 +
trust-anchor-file: trusted-key.key
 +
 
 +
Also make sure that if a general [[#Forwarding queries|forward]] to a DNS server has been set, then comment them out; otherwise, DNS queries will fail. DNSSEC validation will only be done if the DNS server being queried supports it.
 +
 
 +
{{Note|Including DNSSEC checking significantly increases DNS lookup times for initial lookups. Once an address is cached locally, then the lookup is virtually instantaneous.}}
 +
 
 +
To test if DNSSEC is working, use ''drill'':
 +
 
 +
$ drill sigfail.verteiltesysteme.net
 +
$ drill sigok.verteiltesysteme.net
 +
 
 +
The first command should give an {{ic|rcode}} of {{ic|SERVFAIL}}. The second should give an {{ic|rcode}} of {{ic|NOERROR}}.
 +
 
 +
=== Forwarding queries ===
 +
 
 +
{{Tip|Unbound can be used with [[DNSCrypt]] by setting up forwarding. See [[DNSCrypt#Example: configuration for Unbound]].}}
 +
 
 +
If you have a local network which you wish to have DNS queries for and there is a local DNS server that you would like to forward queries to then you should include this line:
  
If you have a local network which you wish to have dns queries for and there is a local dns server that you would like to forward queries to then you should include the line: private-address for say the 10. or 192.168. networks as:  
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private-address: ''local_subnet/subnet_mask''
  
{{ic|private-address: 10.0.0.0/24}}
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For example:
  
or
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private-address: 10.0.0.0/24
  
{{ic|private-address: 192.168.0.0/16}}
+
{{Note|You can use private-address to protect against DNS Rebind attacks. Therefore you may enable RFC1918 networks (10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16 fd00::/8 fe80::/10). Unbound may enable this feature by default in future releases.}}  
  
To include a local dns server for both forward and reverse local addresses a set of lines similar to these below is necessary with a forward and reverse lookup (choose the ip address of the server providing dns for the local network accordingly by changing 10.0.0.1 in the lines below):
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To include a local DNS server for both forward and reverse local addresses a set of lines similar to these below is necessary with a forward and reverse lookup (choose the IP address of the server providing DNS for the local network accordingly by changing 10.0.0.1 in the lines below):
  
 
  local-zone: "10.in-addr.arpa." transparent
 
  local-zone: "10.in-addr.arpa." transparent
Line 67: Line 113:
 
  forward-zone:
 
  forward-zone:
 
  name: "mynetwork.com."
 
  name: "mynetwork.com."
  forward-addr: 10.0.0.1       # Home DNS
+
  forward-addr: 10.0.0.1
  
 
  forward-zone:
 
  forward-zone:
Line 73: Line 119:
 
  forward-addr: 10.0.0.1
 
  forward-addr: 10.0.0.1
  
Note that there is a difference between forward zones and stub zones - stub zones will only work when connected to an authoritative dns server directly. This would work for lookups from a bind dns server if it is providing authoritative dns - but if you are referring queries to an unbound server in which internal lookups are forwarded on to another dns server, then defining the referral as a stub zone in the machine here won't work. In that case it is necessary to define a forward zone as above, since forward zones can have daisy chain lookups onward to other dns servers. i.e. forward zones can refer queries to recursive dns servers. This distinction is important as you don't get any error messages indicating what the problem is if you use a stub zone inappropriately.
+
{{Note|There is a difference between forward zones and stub zones - stub zones will only work when connected to an authoritative DNS server directly. This would work for lookups from a [[BIND]] DNS server if it is providing authoritative DNS - but if you are referring queries to an ''unbound'' server in which internal lookups are forwarded on to another DNS server, then defining the referral as a stub zone in the machine here will not work. In that case it is necessary to define a forward zone as above, since forward zones can have daisy chain lookups onward to other DNS servers. i.e. forward zones can refer queries to recursive DNS servers. This distinction is important as you do not get any error messages indicating what the problem is if you use a stub zone inappropriately.}}
  
 
You can set up the localhost forward and reverse lookups with the following lines:
 
You can set up the localhost forward and reverse lookups with the following lines:
Line 86: Line 132:
 
  local-data: "1.0.0.127.in-addr.arpa. 10800 IN PTR localhost."
 
  local-data: "1.0.0.127.in-addr.arpa. 10800 IN PTR localhost."
  
Then to use specific servers for default forward zones that are outside of the local machine and outside of the local network (i.e. all other queries will be forwarded to them, and then cached) add this to the configuration file (and in this example the first two addresses are the fast google dns servers):
+
Then to use specific servers for default forward zones that are outside of the local machine and outside of the local network (i.e. all other queries will be forwarded to them, and then cached) add this to the configuration file (and in this example the first two addresses are the fast google DNS servers):
  
 
  forward-zone:
 
  forward-zone:
Line 95: Line 141:
 
   forward-addr: 208.67.220.220
 
   forward-addr: 208.67.220.220
  
This will make unbound use Google and OpenDNS servers as the forward zone for external lookups.
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This will make ''unbound'' use Google and OpenDNS servers as the forward zone for external lookups.
  
{{Note|OpenDNS strips DNSSEC records from responses. Do not use the above forward zone if you want to enable DNSSEC validation (below).}}
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{{Note|OpenDNS strips DNSSEC records from responses. Do not use the above forward zone if you want to enable [[#DNSSEC validation]].}}
  
=== Adding unbound to boot process ===
+
== Usage ==
  
Start the service:
+
=== Starting Unbound ===
  
systemctl start unbound
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[[Start/enable]] the {{ic|unbound.service}} systemd service.
  
Then enable it so that it starts at boot once you have tested that it works.
+
=== Remotely control Unbound ===
  
systemctl enable unbound
+
''unbound'' ships with the {{ic|unbound-control}} utility which enables us to remotely administer the unbound server. It is similar to the [[Pdnsd#pdnsd-ctl|pdnsd-ctl]] command of {{Pkg|pdnsd}}.
  
=== Set /etc/resolv.conf to use the local DNS server ===
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==== Setting up unbound-control ====
  
Edit {{ic|/etc/resolv.conf}} (See also [[resolv.conf]]):
+
Before you can start using it, the following steps need to be performed:
  
nameserver 127.0.0.1
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1) Firstly, you need to run the following command
  
Also if you want to be able to use the hostname of local machine names without the fully qualified domain names, then add a line with the local domain such as:
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# unbound-control-setup
  
domain localdomain.com
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which will generate a self-signed certificate and private key for the server, as well as the client. These files will be created in the {{ic|/etc/unbound}} directory.
nameserver 127.0.0.1
+
  
That way you can refer to local hosts such as mainmachine1.localdomain.com as simply mainmachine1 when using the ssh command, but the drill command below still requires the fully qualified domain names in order to perform lookups.
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2) After that, edit {{ic|/etc/unbound/unbound.conf}} and put the following contents in that. The {{ic|control-enable: yes}} option is necessary, the rest can be adjusted as required.
  
Testing the server before making it default can be done using the drill command from the ldns package with examples from internal and external forward and reverse addresses:
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remote-control:
 +
    # Enable remote control with unbound-control(8) here.
 +
    # set up the keys and certificates with unbound-control-setup.
 +
    control-enable: yes
 +
   
 +
    # what interfaces are listened to for remote control.
 +
    # give 0.0.0.0 and ::0 to listen to all interfaces.
 +
    control-interface: 127.0.0.1
 +
   
 +
    # port number for remote control operations.
 +
    control-port: 8953
 +
   
 +
    # unbound server key file.
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    server-key-file: "/etc/unbound/unbound_server.key"
 +
   
 +
    # unbound server certificate file.
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    server-cert-file: "/etc/unbound/unbound_server.pem"
 +
   
 +
    # unbound-control key file.
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    control-key-file: "/etc/unbound/unbound_control.key"
 +
   
 +
    # unbound-control certificate file.
 +
    control-cert-file: "/etc/unbound/unbound_control.pem"
  
drill @127.0.0.1 www.cnn.com
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==== Using unbound-control ====
drill @127.0.0.1 localmachine.localdomain.com
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drill @127.0.0.1 -x w.x.y.z
+
  
where w.x.y.z can be a local or external ip address and the -x option requests a reverse lookup. Once all is working, and you have /etc/resolv.conf set to use 127.0.0.1 as the nameserver then you no longer need the @127.0.0.1 in the drill command, and you can test again that it uses the default dns server - check that the server used as listed at the bottom of the output from each of these commands shows it is 127.0.0.1 being queried.
+
Some of the commands that can be used with ''unbound-control'' are:
  
== Configuring Unbound to Validate DNSSEC ==
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* print statistics without resetting them
 +
  # unbound-control stats_noreset
  
Make sure that the root anchor key file exists as described earlier in the page:
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* dump cache to stdout
 +
  # unbound-control dump_cache
  
Edit unbound.conf, adding the following line to the ''server:'' block:
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* flush cache and reload configuration
 +
  # unbound-control reload
  
    auto-trust-anchor-file: "/etc/unbound/keys/root.key"
+
Please refer to {{ic|man 8 unbound-control}} for a detailed look at the operations it supports.
  
Also make sure that if a general forward to the google servers had been in place, then comment them out otherwise dns queries will fail.
+
== Tips and tricks ==
  
Restart unbound:
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=== Block advertising ===
 +
You can use the following file and simply include it in your unbound configuration: [https://pgl.yoyo.org/adservers/serverlist.php?hostformat=unbound&showintro=0&startdate%5Bday%5D=&startdate%5Bmonth%5D=&startdate%5Byear%5D=&mimetype=plaintext adservers]
 +
{{hc|/etc/unbound/unbound.conf|
 +
...
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include: /etc/unbound/adservers
 +
}}
  
systemctl restart unbound
+
{{Note|In order to return some OK statuses on those hosts, you can change the 127.0.0.1 redirection to a server you control and have that server respond with empty 204 replies, see [http://www.shadowandy.net/2014/04/adblocking-nginx-serving-1-pixel-gif-204-content.htm this page]}}
  
Now dnssec validation will be done if the dns server being queried supports it. Note that including dnssec checking siginificantly increases dns lookup times for initial lookups. Once an address is cached then the lookup is virtually instantaneous.
+
=== Adding an authoritative DNS server ===
  
==Adding an authoritative dns server==
+
For users who wish to run both a validating, recursive, caching DNS server as well as an authoritative DNS server on a single machine then it may be useful to refer to the wiki page [[nsd]] which gives an example of a configuration for such a system.  Having one server for authoritative DNS queries and a separate DNS server for the validating, recursive, caching DNS functions gives increased security over a single DNS server providing all of these functions. Many users have used bind as a single DNS server, and some help on migration from bind to the combination of running nsd and bind is provided in the [[nsd]] wiki page.
  
For users who wish to run both a validating, recursive, caching dns server as well as an authoritative dns server on a single machine then it may be useful to refer to the wiki page [[nsd]] which gives an example of a configuration for such a system.  Having one server for authoritative dns queries and a separate dns server for the validating, recursive, caching dns functions gives increased security over a single dns server providing all of these functions. Many users have used bind as a single dns server, and some help on migration from bind to the combination of running nsd and bind is provided in the [[nsd]] wiki page.
+
=== WAN facing DNS ===
  
==WAN facing dns==
+
It is also possible to change the configuration files and interfaces on which the server is listening so that DNS queries from machines outside of the local network can access specific machines within the LAN. This is useful for web and mail servers which are accessible from anywhere, and the same techniques can be employed as has been achieved using bind for many years, in combination with suitable port forwarding on firewall machines to forward incoming requests to the right machine.
  
It is also possible to change the configuration files and interfaces on which the server is listening so that dns queries from machines outside of the local network can access specific machines within the LAN. This is useful for web and mail servers which are accessible from anywhere, and the same techniques can be employed as has been achieved using bind for many years, in combination with suitable port forwarding on firewall machines to forward incoming requests to the right machine.
+
=== Roothints systemd timer ===
  
==Issues concerning num_threads==
+
Here is an example systemd service and timer that update {{ic|root.hints}} monthly using the method in [[#Root hints]]:
  
The man page for unbound.conf mentions:
+
{{hc|1=/etc/systemd/system/roothints.service|2=
 +
[Unit]
 +
Description=Update root hints for unbound
 +
After=network.target
 +
 
 +
[Service]
 +
ExecStart=/usr/bin/curl -o /etc/unbound/root.hints <nowiki>https://www.internic.net/domain/named.cache</nowiki>
 +
}}
 +
 
 +
{{hc|1=/etc/systemd/system/roothints.timer|2=
 +
[Unit]
 +
Description=Run root.hints monthly
 +
 
 +
[Timer]
 +
OnCalendar=monthly
 +
Persistent=true   
 +
 +
[Install]
 +
WantedBy=timers.target}}
 +
 
 +
[[Start/enable]] the {{ic|roothints.timer}} systemd timer.
 +
 
 +
== Troubleshooting ==
 +
 
 +
=== Issues concerning num-threads ===
 +
 
 +
The man page for {{ic|unbound.conf}} mentions:
  
 
       outgoing-range: <number>
 
       outgoing-range: <number>
 
               Number of ports to open. This number of file  descriptors  can  be  opened  per thread.
 
               Number of ports to open. This number of file  descriptors  can  be  opened  per thread.
  
and some sources suggest that the num-threads parameter should be set to the number of cpu cores. The sample unbound.conf file merely has:
+
and some sources suggest that the {{ic|num-threads}} parameter should be set to the number of cpu cores. The sample {{ic|unbound.conf.example}} file merely has:
  
 
         # number of threads to create. 1 disables threading.
 
         # number of threads to create. 1 disables threading.
 
         # num-threads: 1
 
         # num-threads: 1
  
However it is not possible to arbitrarily increase num-threads above 1 without causing unbound to start with warnings in the logs about exceeding the number of file descriptors. In reality for most users running on small networks or on a single machine it should be unnecessary to seek performance enhancement by increasing num-threads above 1. If you do wish to do so then refer to http://www.unbound.net/documentation/howto_optimise.html and the following rule of thumb should work:
+
However it is not possible to arbitrarily increase {{ic|num-threads}} above {{ic|1}} without causing ''unbound'' to start with warnings in the logs about exceeding the number of file descriptors. In reality for most users running on small networks or on a single machine it should be unnecessary to seek performance enhancement by increasing {{ic|num-threads}} above {{ic|1}}. If you do wish to do so then refer to [http://www.unbound.net/documentation/howto_optimise.html official documentation] and the following rule of thumb should work:
 +
 
 +
:''Set {{ic|num-threads}} equal to the number of CPU cores on the system. E.g. for 4 CPUs with 2 cores each, use 8.''
 +
 
 +
Set the {{ic|outgoing-range}} to as large a value as possible, see the sections in the referred web page above on how to overcome the limit of {{ic|1024}} in total. This services more clients at a time. With 1 core, try {{ic|950}}. With 2 cores, try {{ic|450}}. With 4 cores try {{ic|200}}. The {{ic|num-queries-per-thread}} is best set at half the number of the {{ic|outgoing-range}}.
  
Set num-threads equal to the number of CPU cores on the system. E.g. for 4 CPUs with 2 cores each, use 8.
+
Because of the limit on {{ic|outgoing-range}} thus also limits {{ic|num-queries-per-thread}}, it is better to compile with {{Pkg|libevent}}, so that there is no {{ic|1024}} limit on {{ic|outgoing-range}}. If you need to compile this way for a heavy duty DNS server then you will need to compile the programme from source instead of using the {{Pkg|unbound}} package.
  
Set the outgoing-range to as large a value as possible, see the sections in the referred web page above on how to overcome the limit of 1024 in total.
+
== See also ==
This services more clients at a time. With 1 core, try 950. With 2 cores, try 450. With 4 cores try 200.
+
The num-queries-per-thread is best set at half the number of the outgoing-range.
+
  
Because of the limit on outgoing-range thus also limits num-queries-per-thread, it is better to compile with libevent, so that there is no more 1024 limit on outgoing-range. If you need to compile this way for a heavy duty dns server then you will need to compile the programme from source instead of using the arch package.
+
* [https://fedoraproject.org/wiki/Changes/Default_Local_DNS_Resolver Fedora change to Unbound]
 +
* [https://github.com/jodrell/unbound-block-hosts/ Block hosts that contain advertisements]

Latest revision as of 18:20, 2 September 2016

Related articles

Unbound is a validating, recursive, and caching DNS resolver. According to Wikipedia:Unbound (DNS Server), "Unbound has supplanted the Berkeley Internet Name Domain (BIND) as the default, base-system name server in several open source projects, where it is perceived as smaller, more modern, and more secure for most applications."

Installation

Install the unbound package.

Additionally, the expat package is required for DNSSEC validation.

Configuration

A default configuration is already included at/etc/unbound/unbound.conf. Additionally, there is a commented sample configuration file with other available options located at /etc/unbound/unbound.conf.example. The following sections highlight different settings for the configuration file. See man unbound.conf for other settings and more details.

Unless otherwise specified, any options listed in this section are to be placed under the server section in the configuration like so:

/etc/unbound/unbound.conf
server:
  ...
  setting: value
  ...

Access control

You can specify the interfaces to answer queries from by IP address. To listen on localhost, use the default setting:

interface: 127.0.0.1

To listen on all interfaces, use the following:

interface: 0.0.0.0

To control which systems can access the server by IP address, use the access-control option:

access-control: subnet action

For example:

access-control: 192.168.1.0/24 allow

action can be one of deny (drop message), refuse (polite error reply), allow (recursive ok), or allow_snoop (recursive and nonrecursive ok). By default everything is refused except for localhost.

Root hints

For querying a host that is not cached as an address the resolver needs to start at the top of the server tree and query the root servers to know where to go for the top level domain for the address being queried. Unbound comes with default builtin hints, but it is good practice to use a root-hints file since the builtin hints may become outdated.

First point unbound to the root.hints file:

root-hints: "/etc/unbound/root.hints"

Then, put a root hints file into the unbound configuration directory. The simplest way to do this is to run the command:

# curl -o /etc/unbound/root.hints https://www.internic.net/domain/named.cache

It is a good idea to update root.hints every six months or so in order to make sure the list of root servers is up to date. This can be done manually or by using Systemd/Timers. See #Roothints systemd timer for an example.

Local DNS server

If you want to use unbound as your local DNS server, set your nameserver to 127.0.0.1 in your resolv.conf. You will want to have your nameserver be preserved.

Tip: A simple way to do this is to install the openresolv package and uncomment the line containing name_servers=127.0.0.1 in /etc/resolvconf.conf. Then run resolvconf -u to generate /etc/resolv.conf.

See Resolv.conf#Testing on how to test your settings.

Check specifically that the server being used is 127.0.0.1 after making permanent changes to resolv.conf.

DNSSEC validation

unbound automatically copies the root server trust key anchor file from /etc/trusted-key.key to /etc/unbound/trusted-key.key. To use DNSSEC validation, point unbound to this file by adding the following setting:

trust-anchor-file: trusted-key.key

Also make sure that if a general forward to a DNS server has been set, then comment them out; otherwise, DNS queries will fail. DNSSEC validation will only be done if the DNS server being queried supports it.

Note: Including DNSSEC checking significantly increases DNS lookup times for initial lookups. Once an address is cached locally, then the lookup is virtually instantaneous.

To test if DNSSEC is working, use drill:

$ drill sigfail.verteiltesysteme.net
$ drill sigok.verteiltesysteme.net

The first command should give an rcode of SERVFAIL. The second should give an rcode of NOERROR.

Forwarding queries

Tip: Unbound can be used with DNSCrypt by setting up forwarding. See DNSCrypt#Example: configuration for Unbound.

If you have a local network which you wish to have DNS queries for and there is a local DNS server that you would like to forward queries to then you should include this line:

private-address: local_subnet/subnet_mask

For example:

private-address: 10.0.0.0/24
Note: You can use private-address to protect against DNS Rebind attacks. Therefore you may enable RFC1918 networks (10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16 fd00::/8 fe80::/10). Unbound may enable this feature by default in future releases.

To include a local DNS server for both forward and reverse local addresses a set of lines similar to these below is necessary with a forward and reverse lookup (choose the IP address of the server providing DNS for the local network accordingly by changing 10.0.0.1 in the lines below):

local-zone: "10.in-addr.arpa." transparent

This line above is important to get the reverse lookup to work correctly.

forward-zone:
name: "mynetwork.com."
forward-addr: 10.0.0.1
forward-zone:
name: "10.in-addr.arpa."
forward-addr: 10.0.0.1
Note: There is a difference between forward zones and stub zones - stub zones will only work when connected to an authoritative DNS server directly. This would work for lookups from a BIND DNS server if it is providing authoritative DNS - but if you are referring queries to an unbound server in which internal lookups are forwarded on to another DNS server, then defining the referral as a stub zone in the machine here will not work. In that case it is necessary to define a forward zone as above, since forward zones can have daisy chain lookups onward to other DNS servers. i.e. forward zones can refer queries to recursive DNS servers. This distinction is important as you do not get any error messages indicating what the problem is if you use a stub zone inappropriately.

You can set up the localhost forward and reverse lookups with the following lines:

local-zone: "localhost." static
local-data: "localhost. 10800 IN NS localhost."
local-data: "localhost. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "localhost. 10800 IN A 127.0.0.1"
local-zone: "127.in-addr.arpa." static
local-data: "127.in-addr.arpa. 10800 IN NS localhost."
local-data: "127.in-addr.arpa. 10800 IN SOA localhost. nobody.invalid. 2 3600 1200 604800 10800"
local-data: "1.0.0.127.in-addr.arpa. 10800 IN PTR localhost."

Then to use specific servers for default forward zones that are outside of the local machine and outside of the local network (i.e. all other queries will be forwarded to them, and then cached) add this to the configuration file (and in this example the first two addresses are the fast google DNS servers):

forward-zone:
  name: "."
  forward-addr: 8.8.8.8
  forward-addr: 8.8.4.4
  forward-addr: 208.67.222.222
  forward-addr: 208.67.220.220

This will make unbound use Google and OpenDNS servers as the forward zone for external lookups.

Note: OpenDNS strips DNSSEC records from responses. Do not use the above forward zone if you want to enable #DNSSEC validation.

Usage

Starting Unbound

Start/enable the unbound.service systemd service.

Remotely control Unbound

unbound ships with the unbound-control utility which enables us to remotely administer the unbound server. It is similar to the pdnsd-ctl command of pdnsd.

Setting up unbound-control

Before you can start using it, the following steps need to be performed:

1) Firstly, you need to run the following command

# unbound-control-setup

which will generate a self-signed certificate and private key for the server, as well as the client. These files will be created in the /etc/unbound directory.

2) After that, edit /etc/unbound/unbound.conf and put the following contents in that. The control-enable: yes option is necessary, the rest can be adjusted as required.

remote-control:
    # Enable remote control with unbound-control(8) here.
    # set up the keys and certificates with unbound-control-setup.
    control-enable: yes
   
    # what interfaces are listened to for remote control.
    # give 0.0.0.0 and ::0 to listen to all interfaces.
    control-interface: 127.0.0.1
   
    # port number for remote control operations.
    control-port: 8953
   
    # unbound server key file.
    server-key-file: "/etc/unbound/unbound_server.key"
   
    # unbound server certificate file.
    server-cert-file: "/etc/unbound/unbound_server.pem"
   
    # unbound-control key file.
    control-key-file: "/etc/unbound/unbound_control.key"
   
    # unbound-control certificate file.
    control-cert-file: "/etc/unbound/unbound_control.pem"

Using unbound-control

Some of the commands that can be used with unbound-control are:

  • print statistics without resetting them
 # unbound-control stats_noreset
  • dump cache to stdout
 # unbound-control dump_cache
  • flush cache and reload configuration
 # unbound-control reload

Please refer to man 8 unbound-control for a detailed look at the operations it supports.

Tips and tricks

Block advertising

You can use the following file and simply include it in your unbound configuration: adservers

/etc/unbound/unbound.conf
...
include: /etc/unbound/adservers
Note: In order to return some OK statuses on those hosts, you can change the 127.0.0.1 redirection to a server you control and have that server respond with empty 204 replies, see this page

Adding an authoritative DNS server

For users who wish to run both a validating, recursive, caching DNS server as well as an authoritative DNS server on a single machine then it may be useful to refer to the wiki page nsd which gives an example of a configuration for such a system. Having one server for authoritative DNS queries and a separate DNS server for the validating, recursive, caching DNS functions gives increased security over a single DNS server providing all of these functions. Many users have used bind as a single DNS server, and some help on migration from bind to the combination of running nsd and bind is provided in the nsd wiki page.

WAN facing DNS

It is also possible to change the configuration files and interfaces on which the server is listening so that DNS queries from machines outside of the local network can access specific machines within the LAN. This is useful for web and mail servers which are accessible from anywhere, and the same techniques can be employed as has been achieved using bind for many years, in combination with suitable port forwarding on firewall machines to forward incoming requests to the right machine.

Roothints systemd timer

Here is an example systemd service and timer that update root.hints monthly using the method in #Root hints:

/etc/systemd/system/roothints.service
[Unit]
Description=Update root hints for unbound
After=network.target

[Service]
ExecStart=/usr/bin/curl -o /etc/unbound/root.hints https://www.internic.net/domain/named.cache
/etc/systemd/system/roothints.timer
[Unit]
Description=Run root.hints monthly

[Timer]
OnCalendar=monthly
Persistent=true     
 
[Install]
WantedBy=timers.target

Start/enable the roothints.timer systemd timer.

Troubleshooting

Issues concerning num-threads

The man page for unbound.conf mentions:

     outgoing-range: <number>
             Number of ports to open. This number of file  descriptors  can  be  opened  per thread.

and some sources suggest that the num-threads parameter should be set to the number of cpu cores. The sample unbound.conf.example file merely has:

       # number of threads to create. 1 disables threading.
       # num-threads: 1

However it is not possible to arbitrarily increase num-threads above 1 without causing unbound to start with warnings in the logs about exceeding the number of file descriptors. In reality for most users running on small networks or on a single machine it should be unnecessary to seek performance enhancement by increasing num-threads above 1. If you do wish to do so then refer to official documentation and the following rule of thumb should work:

Set num-threads equal to the number of CPU cores on the system. E.g. for 4 CPUs with 2 cores each, use 8.

Set the outgoing-range to as large a value as possible, see the sections in the referred web page above on how to overcome the limit of 1024 in total. This services more clients at a time. With 1 core, try 950. With 2 cores, try 450. With 4 cores try 200. The num-queries-per-thread is best set at half the number of the outgoing-range.

Because of the limit on outgoing-range thus also limits num-queries-per-thread, it is better to compile with libevent, so that there is no 1024 limit on outgoing-range. If you need to compile this way for a heavy duty DNS server then you will need to compile the programme from source instead of using the unbound package.

See also