DNS (Domain Name System) is like the phonebook of the internet, translating human-friendly domain names into IP addresses. To make browsing faster, your Linux system stores DNS lookups locally in a DNS cache. But sometimes, that cache causes issues—like loading outdated websites, running into connection errors, or struggling with DNS changes.
The quick fix? Flushing your DNS cache.
In this guide, we’ll explain what the DNS cache is, why you might need to clear it, and how to flush it instantly on different Linux distributions.
What Is the DNS Cache in Linux?
The DNS cache is a temporary database your computer keeps to remember recent domain lookups. For example, when you visit example.com, the IP address is stored locally.
Benefits of the cache:
- Faster browsing (no need to resolve domains repeatedly).
- Reduced DNS traffic.
Problems arise when cached records become stale or corrupted, causing:
- Websites failing to load.
- Old IP addresses being used after a DNS update.
- Security issues from DNS spoofing.
Why Flush the DNS Cache?
You may need to flush your DNS cache when:
- A website recently changed its DNS records.
- You encounter repeated “server not found” or connection errors.
- You suspect DNS spoofing or security issues.
- You’re testing DNS changes as a developer or sysadmin.
How to Flush DNS Cache in Linux
Different Linux systems use different DNS caching services. Here are the most common methods:
1. systemd-resolved (Ubuntu 18.04+, Debian, Fedora, etc.)
If your system uses systemd-resolved:
sudo systemd-resolve --flush-caches
Check the cache size:
systemd-resolve --statistics
2. nscd (Name Service Cache Daemon)
Some older distributions use nscd:
sudo /etc/init.d/nscd restart
Or:
sudo service nscd restart
3. dnsmasq
If your system uses dnsmasq:
sudo /etc/init.d/dnsmasq restart
Or:
sudo systemctl restart dnsmasq
4. BIND (named)
For servers running BIND:
sudo rndc flush
Flush a specific zone:
sudo rndc flushname example.com
Quick One-Liners by System
- Ubuntu/Debian (systemd):
sudo systemd-resolve --flush-caches - CentOS/RHEL (nscd):
sudo service nscd restart - Fedora (dnsmasq):
sudo systemctl restart dnsmasq - BIND servers:
sudo rndc flush
Verifying DNS Cache Flush
After flushing, test with:
dig example.com
or
nslookup example.com
If you see updated IPs or reduced response times, your cache was successfully cleared.
Keeping Your DNS Healthy
Regularly maintaining your DNS setup helps avoid many common connection issues. Along with the occasional cache flush, it’s a good idea to keep your system updated, monitor DNS performance, and double-check settings after making changes. These small habits ensure your browsing stays fast, reliable, and secure.
Conclusion
Flushing your Linux DNS cache is quick, easy, and can save you from hours of frustration. Whether you’re a developer testing DNS changes or a user troubleshooting connection issues, knowing these commands keeps your system clean and responsive.
So next time a website doesn’t load correctly, remember: sometimes all it takes is a simple DNS cache flush to get things back on track.