Domain name resolution

From ArchWiki
Jump to navigation Jump to search

zh-CN:Resolv.conf The configuration file for DNS resolvers is /etc/resolv.conf. From its man page:

"The resolver is a set of routines in the C library that provide access to the Internet Domain Name System (DNS). The resolver configuration file contains information that is read by the resolver routines the first time they are invoked by a process. The file is designed to be human readable and contains a list of keywords with values that provide various types of resolver information.
"On a normally configured system this file should not be necessary. The only name server to be queried will be on the local machine; the domain name is determined from the host name and the domain search path is constructed from the domain name."

DNS in Linux

Your ISP (usually) provides working DNS servers, and a router may also add an extra DNS server in case you have your own cache server. Switching between DNS servers does not represent a problem 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 be the reason why you are getting a delay.

Use dig (provided by package dnsutils) before any changes, repeat after making the adjustments in the section below and compare the query time(s):

$ dig

You can also specify a nameserver:

$ dig

Alternative DNS servers

To use alternative DNS servers, edit /etc/resolv.conf and add them to the top of the file so they are used first, optionally removing or commenting out already listed servers.

Note: Changes made to /etc/resolv.conf take effect immediately.


OpenNIC provides free uncensored nameservers with additional features.

Tip: OpenNIC offers many different nameservers located in multiple countries. Pick some of the nearest nameservers for optimal performance.
# OpenNIC IPv4 nameservers (US)


OpenDNS provides free alternative nameservers:

# OpenDNS IPv4 nameservers
# OpenDNS IPv6 nameservers
nameserver 2620:0:ccc::2
nameserver 2620:0:ccd::2


Google's nameservers can be used as an alternative:

# Google IPv4 nameservers
# Google IPv6 nameservers
nameserver 2001:4860:4860::8888
nameserver 2001:4860:4860::8844


Comodo provides another IPv4 set, with optional (non-free) web-filtering. Implied in this feature is that the service hijacks the queries.

# Comodo nameservers 


Yandex.DNS have a 3 models:

# Basic Yandex.DNS - Quick and reliable DNS
# Safe Yandex.DNS - Protection from virus and fraudulent content
# Family Yandex.DNS - Without adult content


UncensoredDNS is a free uncensored DNS resolver who also answers queries on port 5353 if you are behind a firewall blocking outgoing port 53.

# IPv4 nameservers
nameserver    ##
nameserver      ##
# IPv6 nameservers
nameserver 2001:67c:28a4::             ##
nameserver 2002:d596:2a92:1:71:53::    ##

Preserve DNS settings

dhcpcd, netctl, NetworkManager, and various other processes can overwrite /etc/resolv.conf. This is usually desirable behavior, but sometimes DNS settings need to be set manually (e.g. when using a static IP address). There are several ways to accomplish this.

  • If you are using dhcpcd, see #Modify the dhcpcd config below.
  • If you are using netctl and static IP address assignment, do not use the DNS* options in your profile, otherwise resolvconf is called and /etc/resolv.conf overwritten.

Using openresolv

openresolv provides a utility resolvconf, which is a framework for managing multiple DNS configurations. See man 8 resolvconf and man 5 resolvconf.conf for more information.

The configuration is done in /etc/resolvconf.conf and running resolvconf -u will generate /etc/resolv.conf.

Modify the dhcpcd config

dhcpcd's configuration file may be edited to prevent the dhcpcd daemon from overwriting /etc/resolv.conf. To do this, add the following to the last section of /etc/dhcpcd.conf:

nohook resolv.conf

Alternatively, you can create a file called /etc/resolv.conf.head containing your DNS servers. dhcpcd will prepend this file to the beginning of /etc/resolv.conf.

Or you can configure dhcpcd to use the same DNS servers every time. To do this, add the following line at the end of your /etc/dhcpcd.conf:

static domain_name_servers=

Write-protect /etc/resolv.conf

Another way to protect your /etc/resolv.conf from being modified by anything is setting the immutable (write-protection) attribute:

# chattr +i /etc/resolv.conf

Use timeout option to reduce hostname 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