- "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.
OpenDNS provides free alternative nameservers:
# OpenDNS nameservers nameserver 184.108.40.206 nameserver 220.127.116.11
There are also IPv6 servers available:
nameserver [2620:0:ccc::2] nameserver [2620:0:ccd::2]
Fixing problems with Google
OpenDNS hijacks Google-searches by routing all queries through their own servers first. This can be annoying because Google searches may slow down noticeably and it also breaks Google's FeelingLucky feature (e.g., entering digg in your adress bar will open www.digg.com). For the latter, there is a Firefox-addon that brings back the original behaviour. A more elegant solution is to redirect all queries for Google exclusively to your ISP's DNS Server. This can be done with dnsmasq (see Speeding up DNS with dnsmasq for more information).
Google's nameservers can be used as an alternative:
# Google nameservers nameserver 18.104.22.168 nameserver 22.214.171.124
There are also IPv6 servers available:
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 like OpenDNS does.
# Comodo nameservers nameserver 126.96.36.199 nameserver 188.8.131.52
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 NetworkManager, see this thread on how to prevent it from overriding your
- 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
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