Domain name resolution
- "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) before any changes, repeat after making the adjustments in the section below and compare the query time(s):
$ dig www5.yahoo.com
You can also specify a nameserver:
$ dig @ip.of.name.server www5.yahoo.com
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.
/etc/resolv.conftake effect immediately.
OpenNIC provides free uncensored nameservers with additional features.
# OpenNIC IPv4 nameservers (US) nameserver 22.214.171.124 nameserver 126.96.36.199
OpenDNS provides free alternative nameservers:
# OpenDNS IPv4 nameservers nameserver 188.8.131.52 nameserver 184.108.40.206
# 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 nameserver 220.127.116.11 nameserver 18.104.22.168
# 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 nameserver 22.214.171.124 nameserver 126.96.36.199
Yandex.DNS have a 3 models:
# Basic Yandex.DNS - Quick and reliable DNS nameserver 188.8.131.52 nameserver 184.108.40.206
# Safe Yandex.DNS - Protection from virus and fraudulent content nameserver 220.127.116.11 nameserver 18.104.22.168
# Family Yandex.DNS - Without adult content nameserver 22.214.171.124 nameserver 126.96.36.199
UncensoredDNS is a free uncensored DNS resolver who also answers queries on port 5353 if you are behind a firewall blocking outgoing port 53.
# censurfridns.dk IPv4 nameservers nameserver 188.8.131.52 ## anycast.censurfridns.dk nameserver 184.108.40.206 ## ns1.censurfridns.dk
# censurfridns.dk IPv6 nameservers nameserver 2001:67c:28a4:: ## anycast.censurfridns.dk nameserver 2002:d596:2a92:1:71:53:: ## ns1.censurfridns.dk
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
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
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
Alternatively, you can create a file called
/etc/resolv.conf.head containing your DNS servers. dhcpcd will prepend this file to the beginning of
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
static domain_name_servers=220.127.116.11 18.104.22.168
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