How do I flush DNS on Ubuntu?

On Ubuntu with systemd-resolved (default since Ubuntu 16.04): sudo systemd-resolve --flush-caches. Verify with: sudo systemd-resolve --statistics. On older Ubuntu using nscd: sudo /etc/init.d/nscd restart.

How do I flush DNS on CentOS or RHEL?

On CentOS/RHEL 7 and newer with systemd-resolved: sudo systemd-resolve --flush-caches. If using nscd: sudo service nscd restart. If using dnsmasq: sudo service dnsmasq restart.

How do I check which DNS service is running on Linux?

Run: systemctl status systemd-resolved to check if systemd-resolved is active. Try: systemctl status nscd for nscd. Try: systemctl status dnsmasq for dnsmasq. The active service is the one whose status shows "running".

Does Linux have a DNS cache by default?

It depends on the distribution and configuration. Ubuntu with systemd-resolved has DNS caching enabled by default. Minimal server installations often have no local DNS cache at all — each lookup goes directly to the configured DNS server. Desktop distributions are more likely to have caching enabled.

How do I flush DNS on Arch Linux?

Arch Linux with systemd-resolved: sudo systemd-resolve --flush-caches. Arch with dnsmasq: sudo systemctl restart dnsmasq. If running NetworkManager with dnsmasq plugin: sudo systemctl restart NetworkManager.

Linux terminal showing systemd-resolve flush-caches command

Domain Management

How to Flush DNS Cache on Linux (Ubuntu, Debian, CentOS, Arch)

Domain 360 Team

·July 14, 2026·5 min read

Linux DNS flushing depends on which DNS caching service is running — and this varies by distribution and configuration. Unlike Windows (always ipconfig /flushdns) or Mac (two fixed commands), Linux has several possible services.

Step 1: Identify Your DNS Service

systemctl status systemd-resolved systemctl status nscd systemctl status dnsmasq

The one showing "active (running)" is your DNS caching service.

ubuntu flush dns — systemd-resolved (Default on Ubuntu 16.04+)

Ubuntu 18.04, 20.04, 22.04, 24.04, and Fedora all use systemd-resolved by default.

Flush command: sudo systemd-resolve --flush-caches

Verify: sudo systemd-resolve --statistics — look for "Current Cache Size: 0"

ubuntu flush dns cache — nscd (Older Systems)

If systemctl status nscd shows active:

sudo service nscd restart

nscd does not have a flush command — restarting the service clears its cache.

linux flush dns cache — dnsmasq

sudo killall -HUP dnsmasq

Or: sudo systemctl restart dnsmasq

linux clear dns cache — NetworkManager with dnsmasq

Ubuntu desktop may use dnsmasq embedded inside NetworkManager:

sudo systemctl restart NetworkManager

Note: briefly drops and reconnects network connections.

linux refresh dns — All Ubuntu Versions

Ubuntu 24.04: sudo systemd-resolve --flush-caches Ubuntu 22.04: sudo systemd-resolve --flush-caches Ubuntu 20.04: sudo systemd-resolve --flush-caches Ubuntu 18.04: sudo systemd-resolve --flush-caches Ubuntu 16.04: sudo systemd-resolve --flush-caches Ubuntu 14.04: sudo service dns-clean restart (if installed)

Verifying No Cache Exists

Many minimal Linux server installations have no local DNS cache. Every DNS query goes directly to the configured resolver without caching.

Check: systemctl list-units --type=service | grep -E "dns|nscd|resolved"

If nothing relevant appears as active, there is no local cache to flush. DNS changes take effect on the next query automatically.

When Flushing Does Not Resolve the Issue

If DNS flush does not fix the problem, test with public resolvers:

dig @1.1.1.1 yourdomain.com dig @8.8.8.8 yourdomain.com

If these return different results from your local query, your configured resolver is the issue. If they all return the same (wrong) result, it is propagation — the change has not reached these servers yet.

A domain returning NXDOMAIN everywhere may have expired — WHOIS lookup on the domain shows expiry status immediately.

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