Inspecting and changing macOS network settings from Terminal: networksetup, scutil and DNS cache

Goal

Inspect and change basic network configuration — active service, DNS servers, proxies, computer name, current IP — without opening System Settings, and clear a stale DNS cache.

Prerequisites

Terminal; sudo for changes (listing is unprivileged).

Steps

1. List configurable network services in priority order: networksetup -listallnetworkservices.
2. Read or set DNS servers for one service: networksetup -getdnsservers "Wi-Fi"; set them with sudo networksetup -setdnsservers "Wi-Fi" 1.1.1.1 9.9.9.9; restore automatic, DHCP-provided DNS with sudo networksetup -setdnsservers "Wi-Fi" empty.
3. Read or set a web proxy: networksetup -getwebproxy "Wi-Fi"; sudo networksetup -setwebproxy "Wi-Fi" proxy.example.com 8080.
4. Check the effective DNS configuration macOS is actually using, which can differ from a single service's setting once multiple interfaces and search domains merge: scutil --dns.
5. Read or set the computer's network name: scutil --get ComputerName; change it with sudo scutil --set ComputerName "build-agent-03" (update LocalHostName and HostName the same way if they must match).
6. Get the current IPv4 address of a specific interface without parsing ifconfig output: ipconfig getifaddr en0.
7. Flush the DNS resolver cache after a DNS change, so already-cached answers don't mask it during testing: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.

Expected result

networksetup -getdnsservers and scutil --dns reflect the new servers; ipconfig getifaddr en0 returns the interface's current address, or exits non-zero if that interface has none; a repeated query that prompted the flush returns fresh results instead of a stale cached answer.

Limits and test basis

Command syntax for networksetup, scutil, ipconfig and dscacheutil comes from a command reference, since Apple does not publish these tools' flags as a web page. A service-level change takes effect immediately for new connections; a client already connected before the DNS change may keep using the old servers until it reconnects. None of these commands require a reboot; a proxy or DNS change applies to new connections on that service right away. To undo a -setdnsservers or -setwebproxy change, re-run the same subcommand with the previous values, or pass empty (DNS) / the matching -setwebproxystate off (proxy) to fall back to automatic, DHCP-supplied configuration.