Difference between revisions of "Domain name resolution"

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[[Category:Network configuration]]
 
[[Category:Network configuration]]
 
[[de:Resolv.conf]]
 
[[de:Resolv.conf]]
[[es:Resolv.conf]]
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[[es:Domain name resolution]]
 
[[fr:Resolv.conf]]
 
[[fr:Resolv.conf]]
 
[[it:Resolv.conf]]
 
[[it:Resolv.conf]]
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[[zh-hans:Resolv.conf]]
 
[[zh-hans:Resolv.conf]]
 
{{Related articles start}}
 
{{Related articles start}}
{{Related|Alternative DNS services}}
 
 
{{Related|Network configuration}}
 
{{Related|Network configuration}}
 
{{Related articles end}}
 
{{Related articles end}}
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== Name Service Switch ==
 
== Name Service Switch ==
:''"NSS" redirects here. For Mozilla cryptographic libraries, see [[Network Security Services]].''
 
  
The [[Wikipedia:Name Service Switch|Name Service Switch]] (NSS) facility is part of the GNU C Library ({{Pkg|glibc}}) and backs the {{man|3|getaddrinfo}} API, used to resolve domain names. NSS allows system databases to be provided by separate services, whose search order can be configured by the administrator in {{man|5|nsswitch.conf}}. The database responsible for domain name resolution is the {{ic|hosts}} database, for which glibc offers the following services:
+
The [[Wikipedia:Name Service Switch|Name Service Switch]] (NSS) facility is part of the GNU C Library ({{Pkg|glibc}}) and backs the {{man|3|getaddrinfo}} API, used to resolve domain names. NSS allows system databases to be provided by separate services, whose search order can be configured by the administrator in {{man|5|nsswitch.conf}}. The database responsible for domain name resolution is the ''hosts'' database, for which glibc offers the following services:
  
* {{ic|file}}: reads the {{ic|/etc/hosts}} file, see {{man|5|hosts}}
+
* ''file'': reads the {{ic|/etc/hosts}} file, see {{man|5|hosts}}
* {{ic|dns}}: the [[#Glibc resolver|glibc resolver]] which reads {{ic|/etc/resolv.conf}}, see {{man|5|resolv.conf}}
+
* ''dns'': the [[#Glibc resolver|glibc resolver]] which reads {{ic|/etc/resolv.conf}}, see {{man|5|resolv.conf}}
  
 
[[Systemd]] provides three NSS services for hostname resolution:
 
[[Systemd]] provides three NSS services for hostname resolution:
  
* {{man|8|nss-resolve}} - a caching DNS stub resolver, described in [[#Systemd-resolved]]
+
* {{man|8|nss-resolve}} - a caching DNS stub resolver, described in [[systemd-resolved]]
 
* {{man|8|nss-myhostname}} - provides hostname resolution without having to edit {{ic|/etc/hosts}}, described in [[Network configuration#Local hostname resolution]]
 
* {{man|8|nss-myhostname}} - provides hostname resolution without having to edit {{ic|/etc/hosts}}, described in [[Network configuration#Local hostname resolution]]
 
* {{man|8|nss-mymachines}} - provides hostname resolution for the names of local {{man|8|systemd-machined}} containers  
 
* {{man|8|nss-mymachines}} - provides hostname resolution for the names of local {{man|8|systemd-machined}} containers  
  
=== Check if you can resolve domain names ===
+
=== Resolve a domain name using NSS ===
  
NSS databases can be queried with {{man|1|getent}}. You can resolve a domain name through NSS using:
+
NSS databases can be queried with {{man|1|getent}}. A domain name can be resolved through NSS using:
  
 
  $ getent hosts ''domain_name''
 
  $ getent hosts ''domain_name''
  
{{Note|While most programs resolve domain names using NSS, some may read {{ic|resolv.conf}} and/or {{ic|/etc/hosts}} directly. See [[Network configuration#Local hostname resolution]].}}
+
{{Note|While most programs resolve domain names using NSS, some may read {{ic|/etc/resolv.conf}} and/or {{ic|/etc/hosts}} directly. See [[Network configuration#Local hostname resolution]].}}
  
 
== Glibc resolver ==
 
== Glibc resolver ==
Line 42: Line 40:
  
 
{{man|5|resolv.conf}} lists nameservers together with some configuration options.
 
{{man|5|resolv.conf}} lists nameservers together with some configuration options.
Nameservers listed first are tried first, up to three nameservers may be listed. Lines starting with a number sign are ignored.
+
Nameservers listed first are tried first, up to three nameservers may be listed. Lines starting with a number sign ({{ic|#}}) are ignored.
  
{{Note|The glibc resolver does not cache queries. See [[#Performance]] for more information.}}
+
{{Note|The glibc resolver does not cache queries. To improve query lookup time you can set up a caching resolver. See [[#DNS servers]] for more information.}}
  
=== Overwriting of resolv.conf ===
+
=== Overwriting of /etc/resolv.conf ===
  
[[Network manager]]s tend to overwrite {{ic|resolv.conf}}, for specifics see the corresponding section:
+
[[Network manager]]s tend to overwrite {{ic|/etc/resolv.conf}}, for specifics see the corresponding section:
  
 
* [[dhcpcd#resolv.conf]]
 
* [[dhcpcd#resolv.conf]]
Line 54: Line 52:
 
* [[NetworkManager#resolv.conf]]
 
* [[NetworkManager#resolv.conf]]
  
To prevent programs from overwriting {{ic|resolv.conf}} you can also write-protect it by setting the immutable [[file attribute]].
+
To prevent programs from overwriting {{ic|/etc/resolv.conf}} you can also write-protect it by setting the immutable [[file attribute]]:
  
{{Tip|If you want multiple processes to write to {{ic|resolv.conf}}, you can use [[openresolv]].}}
+
# chattr +i /etc/resolv.conf
 +
 
 +
{{Tip|If you want multiple processes to write to {{ic|/etc/resolv.conf}}, you can use [[resolvconf]].}}
  
 
=== Limit lookup time ===
 
=== Limit lookup time ===
Line 66: Line 66:
 
=== Hostname lookup delayed with IPv6 ===
 
=== Hostname lookup delayed with IPv6 ===
  
If you experience a 5 second delay when resolving hostnames it might be due to a DNS-server/Firewall misbehaving and only giving one reply to a parallel A and AAAA request ([http://udrepper.livejournal.com/20948.html source]).
+
If you experience a 5 second delay when resolving hostnames it might be due to a DNS-server/Firewall misbehaving and only giving one reply to a parallel A and AAAA request.[https://udrepper.livejournal.com/20948.html] You can fix that by setting the following option in {{ic|/etc/resolv.conf}}:
You can fix that by setting the following option in {{ic|/etc/resolv.conf}}:
 
  
 
  options single-request
 
  options single-request
Line 73: Line 72:
 
=== Local domain names ===
 
=== Local domain names ===
  
If you want to be able to use the hostname of local machine names without the fully qualified domain names, then add a line to {{ic|resolv.conf}} with the local domain such as:
+
If you want to be able to use the hostname of local machine names without the fully qualified domain names, then add a line to {{ic|/etc/resolv.conf}} with the local domain such as:
  
 
  domain example.com
 
  domain example.com
Line 79: Line 78:
 
That way you can refer to local hosts such as {{ic|mainmachine1.example.com}} as simply {{ic|mainmachine1}} when using the ''ssh'' command, but the ''drill'' command still requires the fully qualified domain names in order to perform lookups.
 
That way you can refer to local hosts such as {{ic|mainmachine1.example.com}} as simply {{ic|mainmachine1}} when using the ''ssh'' command, but the ''drill'' command still requires the fully qualified domain names in order to perform lookups.
  
== Systemd-resolved ==
+
== Lookup utilities ==
  
{{man|8|systemd-resolved}} is a [[systemd]] service that provides network name resolution to local applications via a [[D-Bus]] interface, the {{ic|resolve}} NSS service ({{man|8|nss-resolve}}), and a local DNS stub listener on {{ic|127.0.0.53}}.  
+
To query specific DNS servers and DNS/[[DNSSEC]] records you can use dedicated DNS lookup utilities. These tools implement DNS themselves and do not use [[#Name Service Switch|NSS]].
  
''systemd-resolved'' has four different modes for handling the [[#Glibc resolver|glibc resolver]]'s ''resolv.conf'' (described in {{man|8|systemd-resolved|/ETC/RESOLV.CONF}}). We will focus here on the two most relevant modes.
+
* {{Pkg|ldns}} provides {{man|1|drill}}, which is a tool designed to retrieve information out of the DNS.
  
# The mode in which ''systemd-resolved'' is a client of the {{ic|/etc/resolv.conf}}. This mode preserves {{ic|/etc/resolv.conf}} and is '''compatible''' with the procedures described in this page.
+
For example, to query a specific nameserver with ''drill'' for the TXT records of a domain:
# The ''systemd-resolved'''s '''recommended''' mode of operation: the DNS stub file {{ic|/run/systemd/resolve/stub-resolv.conf}} contains both the local stub {{ic|127.0.0.53}} as the only DNS servers and a list of search domains.
 
  
The service users are advised to redirect the {{ic|/etc/resolv.conf}} file to the local stub DNS resolver file {{ic|/run/systemd/resolve/stub-resolv.conf}} managed by ''systemd-resolved''. This propagates the systemd managed configuration to all the clients. This can be done by replacing {{ic|/etc/resolv.conf}} with a symbolic link to the systemd stub:
+
$ drill @''nameserver'' TXT ''domain''
 +
 
 +
If you do not specify a DNS server ''drill'' uses the nameservers defined in {{ic|/etc/resolv.conf}}.
  
# ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
+
* {{Pkg|bind-tools}} provides {{man|1|dig}}, {{man|1|host}}, {{man|1|nslookup}} and a bunch of {{ic|dnssec-}} tools.
  
In this mode, the DNS servers are provided in the {{man|5|resolved.conf}} file:
+
== Resolver performance ==
  
{{hc|/etc/systemd/resolved.conf.d/dns_servers.conf|2=
+
The Glibc resolver does not cache queries. If you want local caching use [[systemd-resolved]] or set up a local caching [[#DNS servers|DNS server]] and use {{ic|127.0.0.1}} as your name server.
[Resolve]
 
'''DNS=91.239.100.100 89.233.43.71'''
 
}}
 
  
In order to check the DNS actually used by ''systemd-resolved'', the command to use is:
+
{{Tip|
 +
* The ''drill'' or ''dig'' [[#Lookup utilities|lookup utilities]] report the query time.
 +
* A router usually sets its own caching resolver as the network's DNS server thus providing DNS cache for the whole network.
 +
* If it takes too long to switch to the next DNS server you can try [[#Limit lookup time|decreasing the timeout]].}}
  
$ resolvectl status
+
== Privacy and security ==
  
{{Tip|
+
The DNS protocol is unencrypted and does not account for confidentiality, integrity or authentication, so if you use an untrusted network or a malicious ISP, your DNS queries can be eavesdropped and the responses [[Wikipedia:Man-in-the-middle attack|manipulated]]. Furthermore, DNS servers can conduct [[Wikipedia:DNS hijacking|DNS hijacking]].
* To understand the context around the DNS choices and switches, one can turn on detailed debug information for ''systemd-resolved'' as described in [[Systemd#Diagnosing a service]].
 
* The mode of operation of ''systemd-resolved'' is detected automatically, depending on whether {{ic|/etc/resolv.conf}} is a symlink to the local stub DNS resolver file or contains server names.
 
}}
 
  
== Performance ==
+
You need to trust your DNS server to treat your queries confidentially. DNS servers are provided by ISPs and [[#Third-party DNS services|third-parties]]. Alternatively you can run your own [[#DNS servers|recursive name server]], which however takes more effort. If you use a [[DHCP]] client in untrusted networks, be sure to set static name servers to avoid using and being subject to arbitrary DNS servers. To secure your communication with a remote DNS server you can use an encrypted protocol, like [[Wikipedia:DNS over TLS|DNS over TLS]], [[Wikipedia:DNS over HTTPS|DNS over HTTPS]] or [[Wikipedia:DNSCrypt|DNSCrypt]], provided that both the upstream server and your [[#DNS servers|resolver]] support the protocol. To verify that responses are actually from [[Wikipedia:Authoritative name server|authoritative name servers]], you can validate [[DNSSEC]], provided that both the upstream server(s) and your [[#DNS servers|resolver]] support it.
  
The [[#Glibc resolver]] does not cache queries. If you want local caching use [[#Systemd-resolved]] or set up a local caching [[DNS server]] and use {{ic|127.0.0.1}}.
+
Be aware that client software, such as major web browsers, may also (start to) implement some of the protocols. While the encryption of queries may often be seen as a bonus, it also means the software sidetracks queries around the system resolver configuration.[https://hacks.mozilla.org/2018/05/a-cartoon-intro-to-dns-over-https/#trr-and-doh]
  
{{Tip|The ''drill'' or ''dig'' [[#Lookup utilities]] report the query time.}}
+
== Third-party DNS services ==
  
Internet service providers usually provide working DNS servers. A router may also add an extra DNS server in case it has its own cache server. Switching between DNS servers is transparent for Windows users, because if a DNS server is slow or does not work it will immediately switch to a better one. However, Linux usually takes longer to timeout, which could cause delays.
+
{{Note|Before using a third-party DNS service, check its privacy policy for information on how user data is handled. User data has value and can be sold to other parties.}}
  
== Privacy ==
+
There are various [[Wikipedia:Public recursive name server#List of public DNS service operators|third-party DNS services]] available, some of which also have dedicated software:
  
Most DNS servers keep a log of IP addresses and sites visited on a more or less temporary basis. The data collected can be used to perform various statistical studies. Personally-identifying information have value and can also be rented or sold to third parties. [[Alternative DNS services]] provides a list of popular services, check their privacy policy for information about how user data is handled.
+
* {{App|dingo|A DNS client for Google DNS over HTTPS|https://github.com/pforemski/dingo|{{Pkg|dingo}}}}
 +
* {{App|opennic-up|Automates the renewal of the DNS servers with the most responsive OpenNIC servers|https://github.com/kewlfft/opennic-up|{{AUR|opennic-up}}}}
  
== Lookup utilities ==
+
== DNS servers ==
  
To query specific DNS servers and DNS/[[DNSSEC]] records you can use dedicated DNS lookup utilities. These tools implement DNS themselves and do not use [[#Name Service Switch|NSS]].
+
[[DNS]] servers can be [[Wikipedia:Authoritative name server|authoritative]] and [[Wikipedia:Name server#Recursive query|recursive]]. If they are neither, they are called '''stub resolvers''' and simply forward all queries to another recursive name server. Stub resolvers are typically used to introduce DNS caching on the local host or network. Note that the same can also be achieved with a fully-fledged name server. This section compares the available DNS servers, for a more detailed comparison, refer to [[Wikipedia:Comparison of DNS server software|Wikipedia]].
  
* {{Pkg|ldns}} provides {{man|1|drill}}, which is a tool designed to retrieve information out of the DNS.
+
{{Expansion|Fill in the unknowns. Add {{AUR|deadwood}}.}}
  
For example, to query a specific nameserver with ''drill'' for the TXT records of a domain:
+
{| class="wikitable sortable" style="text-align:center"
 +
! Name !! Package !! [[Wikipedia:Authoritative name server|Authoritative]]<br>/ [[Wikipedia:Name server#Recursive query|Recursive]] !! [[Wikipedia:Name server#Caching name server|Cache]] !! [[resolvconf]] !!  [[Wikipedia:Domain Name System Security Extensions#The lookup procedure|Validates]]<br>[[DNSSEC]] !! [[Wikipedia:DNS over TLS|DNS<br>over TLS]] !! [[Wikipedia:DNS over HTTPS|DNS<br>over HTTPS]]
 +
|-
 +
! [[dnscrypt-proxy]]<sup>1</sup>
 +
| {{Pkg|dnscrypt-proxy}} || {{No}} || {{Yes}} || {{No}} || {{No}} || {{No}} || {{Yes}}
 +
|-
 +
! [[Rescached]]
 +
| {{AUR|rescached-git}} || {{No}} || {{Yes}} || {{Yes|https://github.com/shuLhan/rescached-go#integration-with-openresolv}} || {{No}} || {{No}} || {{Y|Limited}}<sup>2</sup>
 +
|-
 +
! [[Stubby]]
 +
| {{Pkg|stubby}} || {{No}} || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}}
 +
|-
 +
!style="white-space: nowrap;"| [[systemd-resolved]]
 +
| {{Pkg|systemd}} || {{No}} || {{Yes}} || {{G|[[systemd-resolvconf|Yes]]}} || {{Yes}} || {{Y|Insecure}}<sup>3</sup> || {{No|https://github.com/systemd/systemd/issues/8639}}
 +
|-
 +
! [[dnsmasq]]
 +
| {{Pkg|dnsmasq}} || {{Y|Partial}}<sup>4</sup> || {{Yes}} || {{G|[[openresolv#Subscribers|Yes]]}} || {{Yes}} || {{No|http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2018q2/012131.html}} || {{No}}
 +
|-
 +
! [[BIND]]
 +
| {{Pkg|bind}} || {{Yes}} || {{Yes}} || {{G|[[openresolv#Subscribers|Yes]]}} || {{Yes}} || ? || ?
 +
|-
 +
! [[Knot Resolver]]
 +
| {{AUR|knot-resolver}} || {{Yes}} || {{Yes}} || {{No}} || {{Yes}} || {{Yes}} || {{No|https://gitlab.labs.nic.cz/knot/knot-resolver/issues/243}}
 +
|-
 +
! [[Wikipedia:MaraDNS|MaraDNS]]
 +
| {{AUR|maradns}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || {{No}} || {{No}}
 +
|-
 +
! [[pdnsd]]
 +
| {{Pkg|pdnsd}} || {{Yes}} || {{G|Permanent}} || {{G|[[openresolv#Subscribers|Yes]]}} || {{No}} || {{No}} || {{No}}
 +
|-
 +
! [https://www.powerdns.com/recursor.html PowerDNS Recursor]
 +
| {{Pkg|powerdns-recursor}} || {{Yes}} || {{Yes}} || {{No|https://roy.marples.name/projects/openresolv/config#pdns_recursor}} || {{Yes}} || ? || ?
 +
|-
 +
! [[Unbound]]
 +
| {{Pkg|unbound}} || {{Yes}} || {{Yes}} || {{G|[[openresolv#Subscribers|Yes]]}} || {{Yes}} || {{Yes}} || {{No|1=https://nlnetlabs.nl/bugs-script/show_bug.cgi?id=1200}}
 +
|}
  
$ drill @''nameserver'' TXT ''domain''
+
# Implements a [[Wikipedia:DNSCrypt|DNSCrypt]] protocol client.
 +
# Only forwards using DNS over HTTPS when Rescached itself is queried using DNS over HTTPS.[https://github.com/shuLhan/rescached-go#integration-with-dns-over-https]
 +
# From {{man|5|resolved.conf}}: ''Note as the resolver is not capable of authenticating the server, it is vulnerable for "man-in-the-middle" attacks.''[https://github.com/systemd/systemd/issues/9397] Also, the only supported mode is "opportunistic", which ''makes DNS-over-TLS vulnerable to "downgrade" attacks''.[https://github.com/systemd/systemd/issues/10755]
 +
# From [[Wikipedia:Comparison_of_DNS_server_software#cite_note-masqauth-26|Wikipedia]]: dnsmasq has limited authoritative support, intended for internal network use rather than public Internet use.
  
If you do not specify a DNS server ''drill'' uses the nameservers defined in {{ic|/etc/resolv.conf}}.
+
=== Authoritative-only servers ===
  
* {{Pkg|bind-tools}} provides {{man|1|dig}}, {{man|1|host}}, {{man|1|nslookup}} and a bunch of {{ic|dnssec-}} tools.
+
{| class="wikitable sortable" style="text-align:center"
 +
! Name !! Package !!  [[DNSSEC]] !! Geographic<br>balancing
 +
|-
 +
! [https://gdnsd.org/ gdnsd]
 +
| {{Pkg|gdnsd}} || {{No}} || {{Yes}}
 +
|-
 +
! [https://www.knot-dns.cz/ Knot DNS]
 +
| {{Pkg|knot}} || {{Yes}} || {{No}}
 +
|-
 +
! [[NSD]]
 +
| {{Pkg|nsd}} || {{No}} || {{No}}
 +
|-
 +
! [https://www.powerdns.com/auth.html PowerDNS]
 +
| {{Pkg|powerdns}} || {{Yes}} || {{Yes}}
 +
|}
  
 
== See also ==
 
== See also ==
Line 138: Line 188:
 
* [https://www.tldp.org/LDP/nag2/x-087-2-resolv.html Linux Network Administrators Guide]
 
* [https://www.tldp.org/LDP/nag2/x-087-2-resolv.html Linux Network Administrators Guide]
 
* [https://www.debian.org/doc/manuals/debian-handbook/sect.hostname-name-service.en.html#sect.name-resolution Debian Handbook]
 
* [https://www.debian.org/doc/manuals/debian-handbook/sect.hostname-name-service.en.html#sect.name-resolution Debian Handbook]
 +
* [[RFC:7706]] - Decreasing Access Time to Root Servers by Running One on Loopback

Latest revision as of 19:18, 9 January 2019

In general, a domain name represents an IP address and is associated to it in the Domain Name System (DNS). This article explains how to configure domain name resolution and resolve domain names.

Name Service Switch

The Name Service Switch (NSS) facility is part of the GNU C Library (glibc) and backs the getaddrinfo(3) API, used to resolve domain names. NSS allows system databases to be provided by separate services, whose search order can be configured by the administrator in nsswitch.conf(5). The database responsible for domain name resolution is the hosts database, for which glibc offers the following services:

Systemd provides three NSS services for hostname resolution:

Resolve a domain name using NSS

NSS databases can be queried with getent(1). A domain name can be resolved through NSS using:

$ getent hosts domain_name
Note: While most programs resolve domain names using NSS, some may read /etc/resolv.conf and/or /etc/hosts directly. See Network configuration#Local hostname resolution.

Glibc resolver

The glibc resolver reads /etc/resolv.conf for every resolution to determine the nameservers and options to use.

resolv.conf(5) lists nameservers together with some configuration options. Nameservers listed first are tried first, up to three nameservers may be listed. Lines starting with a number sign (#) are ignored.

Note: The glibc resolver does not cache queries. To improve query lookup time you can set up a caching resolver. See #DNS servers for more information.

Overwriting of /etc/resolv.conf

Network managers tend to overwrite /etc/resolv.conf, for specifics see the corresponding section:

To prevent programs from overwriting /etc/resolv.conf you can also write-protect it by setting the immutable file attribute:

# chattr +i /etc/resolv.conf
Tip: If you want multiple processes to write to /etc/resolv.conf, you can use resolvconf.

Limit lookup time

If you are confronted with a very long hostname lookup (may it be in pacman or while browsing), it often helps to define a small timeout after which an alternative nameserver is used. To do so, put the following in /etc/resolv.conf.

options timeout:1

Hostname lookup delayed with IPv6

If you experience a 5 second delay when resolving hostnames it might be due to a DNS-server/Firewall misbehaving and only giving one reply to a parallel A and AAAA request.[1] You can fix that by setting the following option in /etc/resolv.conf:

options single-request

Local domain names

If you want to be able to use the hostname of local machine names without the fully qualified domain names, then add a line to /etc/resolv.conf with the local domain such as:

domain example.com

That way you can refer to local hosts such as mainmachine1.example.com as simply mainmachine1 when using the ssh command, but the drill command still requires the fully qualified domain names in order to perform lookups.

Lookup utilities

To query specific DNS servers and DNS/DNSSEC records you can use dedicated DNS lookup utilities. These tools implement DNS themselves and do not use NSS.

  • ldns provides drill(1), which is a tool designed to retrieve information out of the DNS.

For example, to query a specific nameserver with drill for the TXT records of a domain:

$ drill @nameserver TXT domain

If you do not specify a DNS server drill uses the nameservers defined in /etc/resolv.conf.

Resolver performance

The Glibc resolver does not cache queries. If you want local caching use systemd-resolved or set up a local caching DNS server and use 127.0.0.1 as your name server.

Tip:
  • The drill or dig lookup utilities report the query time.
  • A router usually sets its own caching resolver as the network's DNS server thus providing DNS cache for the whole network.
  • If it takes too long to switch to the next DNS server you can try decreasing the timeout.

Privacy and security

The DNS protocol is unencrypted and does not account for confidentiality, integrity or authentication, so if you use an untrusted network or a malicious ISP, your DNS queries can be eavesdropped and the responses manipulated. Furthermore, DNS servers can conduct DNS hijacking.

You need to trust your DNS server to treat your queries confidentially. DNS servers are provided by ISPs and third-parties. Alternatively you can run your own recursive name server, which however takes more effort. If you use a DHCP client in untrusted networks, be sure to set static name servers to avoid using and being subject to arbitrary DNS servers. To secure your communication with a remote DNS server you can use an encrypted protocol, like DNS over TLS, DNS over HTTPS or DNSCrypt, provided that both the upstream server and your resolver support the protocol. To verify that responses are actually from authoritative name servers, you can validate DNSSEC, provided that both the upstream server(s) and your resolver support it.

Be aware that client software, such as major web browsers, may also (start to) implement some of the protocols. While the encryption of queries may often be seen as a bonus, it also means the software sidetracks queries around the system resolver configuration.[2]

Third-party DNS services

Note: Before using a third-party DNS service, check its privacy policy for information on how user data is handled. User data has value and can be sold to other parties.

There are various third-party DNS services available, some of which also have dedicated software:

  • dingo — A DNS client for Google DNS over HTTPS
https://github.com/pforemski/dingo || dingo
  • opennic-up — Automates the renewal of the DNS servers with the most responsive OpenNIC servers
https://github.com/kewlfft/opennic-up || opennic-upAUR

DNS servers

DNS servers can be authoritative and recursive. If they are neither, they are called stub resolvers and simply forward all queries to another recursive name server. Stub resolvers are typically used to introduce DNS caching on the local host or network. Note that the same can also be achieved with a fully-fledged name server. This section compares the available DNS servers, for a more detailed comparison, refer to Wikipedia.

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

Reason: Fill in the unknowns. Add deadwoodAUR. (Discuss in Talk:Domain name resolution#)
Name Package Authoritative
/ Recursive
Cache resolvconf Validates
DNSSEC
DNS
over TLS
DNS
over HTTPS
dnscrypt-proxy1 dnscrypt-proxy No Yes No No No Yes
Rescached rescached-gitAUR No Yes Yes No No Limited2
Stubby stubby No No No Yes Yes No
systemd-resolved systemd No Yes Yes Yes Insecure3 No
dnsmasq dnsmasq Partial4 Yes Yes Yes No No
BIND bind Yes Yes Yes Yes ? ?
Knot Resolver knot-resolverAUR Yes Yes No Yes Yes No
MaraDNS maradnsAUR Yes Yes No No No No
pdnsd pdnsd Yes Permanent Yes No No No
PowerDNS Recursor powerdns-recursor Yes Yes No Yes ? ?
Unbound unbound Yes Yes Yes Yes Yes No
  1. Implements a DNSCrypt protocol client.
  2. Only forwards using DNS over HTTPS when Rescached itself is queried using DNS over HTTPS.[3]
  3. From resolved.conf(5): Note as the resolver is not capable of authenticating the server, it is vulnerable for "man-in-the-middle" attacks.[4] Also, the only supported mode is "opportunistic", which makes DNS-over-TLS vulnerable to "downgrade" attacks.[5]
  4. From Wikipedia: dnsmasq has limited authoritative support, intended for internal network use rather than public Internet use.

Authoritative-only servers

Name Package DNSSEC Geographic
balancing
gdnsd gdnsd No Yes
Knot DNS knot Yes No
NSD nsd No No
PowerDNS powerdns Yes Yes

See also