---
id: agent-linux-dns-resolution-and-name-service-switch
title: 'Agent Linux DNS Resolution and Name Service Switch'
schema_type: TechArticle
category: ai
language: en
confidence: medium
last_verified: '2026-06-03'
created_date: '2026-06-03'
generation_method: ai_structured
derived_from_human_seed: true
conflict_of_interest: none_declared
is_live_document: false
data_period: static
atomic_facts:
  - id: fact-ai-agent-linux-dns-resolution-and-name-service-switch-1
    statement: >-
      The resolv.conf manual describes /etc/resolv.conf as the resolver
      configuration file read by resolver routines when they are first invoked.
    source_title: resolv.conf Linux Manual Page
    source_url: https://man7.org/linux/man-pages/man5/resolv.conf.5.html
    confidence: medium
  - id: fact-ai-agent-linux-dns-resolution-and-name-service-switch-2
    statement: >-
      The resolv.conf manual says nameserver entries list name server IP
      addresses and that multiple servers are queried in listed order.
    source_title: resolv.conf Linux Manual Page
    source_url: https://man7.org/linux/man-pages/man5/resolv.conf.5.html
    confidence: medium
  - id: fact-ai-agent-linux-dns-resolution-and-name-service-switch-3
    statement: >-
      The nsswitch.conf manual says /etc/nsswitch.conf determines the sources
      and order used to obtain name-service information.
    source_title: nsswitch.conf Linux Manual Page
    source_url: https://man7.org/linux/man-pages/man5/nsswitch.conf.5.html
    confidence: medium
completeness: 0.82
known_gaps:
  - Linux name resolution evidence depends on libc implementation, systemd-resolved, container DNS injection, /etc/hosts, search domains, ndots, per-process resolver environment variables, caching daemons, split DNS, VPN routing, and whether the failing process has already cached resolver configuration.
disputed_statements: []
primary_sources:
  - title: resolv.conf Linux Manual Page
    type: documentation
    year: 2026
    url: https://man7.org/linux/man-pages/man5/resolv.conf.5.html
    institution: man7.org Linux manual pages
  - title: nsswitch.conf Linux Manual Page
    type: documentation
    year: 2026
    url: https://man7.org/linux/man-pages/man5/nsswitch.conf.5.html
    institution: man7.org Linux manual pages
secondary_sources: []
updated: '2026-06-03'
ai_models:
  - gpt-5-codex
---

## TL;DR

Linux DNS and NSS evidence lets agents separate network reachability, resolver configuration, and host database lookup failures.

## Core Explanation

When an application cannot resolve a hostname, the answer may be in resolver configuration rather than in the application code. Agents should capture `/etc/resolv.conf`, `/etc/nsswitch.conf`, `/etc/hosts`, container runtime DNS settings, search domains, resolver options, and the exact hostname queried before changing code or restarting services.

The key distinction is that DNS is only one possible name-service source. NSS controls whether hosts, files, DNS, LDAP, or other services are consulted and in what order. A safe agent reports the process and namespace whose resolver state it inspected because container and host views often differ.

## Source-Mapped Facts

- The resolv.conf manual describes /etc/resolv.conf as the resolver configuration file read by resolver routines when they are first invoked. ([source](https://man7.org/linux/man-pages/man5/resolv.conf.5.html))
- The resolv.conf manual says nameserver entries list name server IP addresses and that multiple servers are queried in listed order. ([source](https://man7.org/linux/man-pages/man5/resolv.conf.5.html))
- The nsswitch.conf manual says /etc/nsswitch.conf determines the sources and order used to obtain name-service information. ([source](https://man7.org/linux/man-pages/man5/nsswitch.conf.5.html))

## Further Reading

- [resolv.conf Linux Manual Page](https://man7.org/linux/man-pages/man5/resolv.conf.5.html)
- [nsswitch.conf Linux Manual Page](https://man7.org/linux/man-pages/man5/nsswitch.conf.5.html)