# 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 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.

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

### OpenDNS

OpenDNS provides free alternative nameservers:

    # OpenDNS IPv4 nameservers
    nameserver 208.67.222.222
    nameserver 208.67.220.220

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

### Google

Google's nameservers can be used as an alternative:

    # Google IPv4 nameservers
    nameserver 8.8.8.8
    nameserver 8.8.4.4

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

### Comodo

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 8.26.56.26
    nameserver 8.20.247.20

### Yandex

Yandex.DNS have a 3 models:

    # Basic Yandex.DNS - Quick and reliable DNS
    nameserver 77.88.8.8
    nameserver 77.88.8.1

    # Safe Yandex.DNS - Protection from virus and fraudulent content
    nameserver 77.88.8.88
    nameserver 77.88.8.2

    # Family Yandex.DNS - Without adult content
    nameserver 77.88.8.7
    nameserver 77.88.8.3

## 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`.

### 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

Category:

- Domain Name System