resolv.conf is the name of a

computer file A computer file is a computer resource for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so can data be written to a computer file. Files can be shared with and trans ...

used in various operating systems to configure the system's

Domain Name System The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned t ...

(DNS) resolver. The file is a plain-text file usually created by the network administrator or by applications that manage the configuration tasks of the system. The resolvconf program is one such program on

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

or other

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

machines which manages the resolv.conf file.

Purpose

In most

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

s and others that implement the

BIND BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name daemon''), performs both of the main DNS server roles, acting as an authoritative ...

(DNS) resolver library, the ''resolv.conf''

configuration file In computing, configuration files (commonly known simply as config files) are files used to configure the parameters and initial settings for some computer programs. They are used for user applications, server processes and operating system ...

contains information that determines the operational parameters of the DNS resolver. The DNS resolver allows applications running in the operating system to translate human-friendly

domain name A domain name is a string that identifies a realm of administrative autonomy, authority or control within the Internet. Domain names are often used to identify services provided through the Internet, such as websites, email services and more. As ...

s into the numeric

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

es that are required for access to resources on the

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a large ...

or the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...

. The process of determining IP addresses from domain names is called address resolution.

Contents and location

The file ''resolv.conf'' typically contains ''search'' directives that specify the default search domains used for completing a given query name to a

fully qualified domain name A fully qualified domain name (FQDN), sometimes also referred to as an ''absolute domain name'', is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including th ...

when no domain suffix is supplied. For instance, ''search example.com local.test'' configures the resolver to try additionally ''somehost.example.com'' and ''somehost.local.test''. It also contains a list of IP addresses of nameservers for resolution. For instance, ''nameserver 1.1.1.1'' configures the resolver to query for the name server with IP 1.1.1.1. Additional ''nameserver'' directives after the first are only used when the first or last used server is unavailable. An example file is: search example.com local.test nameserver 10.0.0.17 nameserver 10.1.0.12 nameserver 10.16.0.7 ''resolv.conf'' is usually located in the directory '' /etc'' of the

file system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

. The file is either maintained manually, or when

DHCP The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a cli ...

is used, it is usually updated with the utility resolvconf. In

systemd systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manag ...

based Linux distributions using systemd-resolved.service, ''/etc/resolv.conf'' is a symlink to ''/run/systemd/resolve/stub-resolv.conf''.

References

External links

"resolv.conf"
on

Arch Linux Arch Linux () is an independently developed, x86-64 general-purpose Linux distribution that strives to provide the latest stable versions of most software by following a rolling-release model. The default installation is a minimal base system, ...

wiki
"resolv.conf"
on

Gentoo Linux Gentoo Linux (pronounced ) is a Linux distribution built using the Portage package management system. Unlike a binary software distribution, the source code is compiled locally according to the user's preferences and is often optimized for th ...

wiki * * * {{man, 5, resolv.conf, OpenBSD Domain Name System Configuration files

Purpose

Contents and location

See also

References

External links