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How to Clear DNS Cache on Linux

This guide will show you how to flush the DNS resolver cache on a Linux system. You will learn the terminal commands for the most common DNS caching services, helping to resolve website loading errors, outdated domain records, and general connectivity issues related to domain name resolution.

Note: Steps may vary by device and router model. This guide focuses on safe, general methods.

Quick Answer

Open a terminal window.
Identify your DNS caching service (common ones are systemd-resolved, nscd, or dnsmasq).
For systemd-resolved: Run sudo systemd-resolve --flush-caches
For nscd: Run sudo systemctl restart nscd
For dnsmasq: Run sudo systemctl restart dnsmasq
Verify the cache is cleared by checking the service status.

If this doesn’t work, your system may use a different resolver or the issue might not be DNS-related. Follow the diagnostic flow below.

What you need

Before you start

Access to a terminal on your Linux machine.
Administrator (sudo) privileges.
Basic knowledge of your Linux distribution (e.g., Ubuntu, Fedora, Arch).
A working internet connection to verify results.
Patience—changes take effect immediately but might not solve all issues.

Good to know

DNS cache stores recent domain name lookups to speed up browsing.
Clearing it forces your system to fetch fresh records from upstream DNS servers.
This is a temporary, non-destructive operation.
Different Linux distributions use different default DNS caching services.
You may need to identify which service is active on your system.

Diagnose the issue in 2 minutes

Is it only one device or all devices on your network?
- One device: The problem is likely with this Linux machine. Proceed below.
- All devices: The problem is likely with your router or ISP. Try restarting your router first.
On the affected Linux machine, can you ping an IP address?
- Run: ping -c 4 8.8.8.8
- Success: You have a basic internet connection. The issue may be DNS.
- Failure: You have a general network problem (Wi-Fi, Ethernet, router).
Can you resolve a domain name?
- Run: nslookup google.com or host google.com
- Success (returns an IP): DNS is working, but the cache might have a stale entry for a specific site.
- Failure (no answer or error): Your DNS resolver is failing. Clearing the cache or changing DNS servers may help.
Is a VPN or custom proxy active? Disable it temporarily to see if the issue resolves.

Step-by-step guide

Step 1 — Open a terminal

You need command-line access. Use your desktop environment's shortcut (often Ctrl+Alt+T) or open it from the applications menu.

Step 2 — Check for an active DNS caching service

Determine which service is managing DNS cache on your system.

Check for systemd-resolved: systemctl is-active systemd-resolved
Check for nscd: systemctl is-active nscd
Check for dnsmasq: systemctl is-active dnsmasq

What you should see: "active" for one of these services. If all are "inactive", your system may not have a local DNS cache.

Step 3 — Clear the systemd-resolved cache (common on modern distros)

If systemd-resolved is active, use this command.

Run: sudo systemd-resolve --flush-caches
Verify: sudo systemd-resolve --statistics (look for "Current Cache Size: 0")

Step 4 — Restart the nscd service

If nscd (Name Service Cache Daemon) is active, restarting it clears the cache.

Run: sudo systemctl restart nscd
Verify: systemctl status nscd should show "active (running)".

Step 5 — Restart the dnsmasq service

If dnsmasq is acting as your local DNS cache, restart it.

Run: sudo systemctl restart dnsmasq

Step 6 — Alternative: Restart networking (broad approach)

If unsure or the above didn't work, a network restart can clear various caches.

Using systemd-networkd: sudo systemctl restart systemd-networkd
Using NetworkManager: sudo systemctl restart NetworkManager

What you should see: Your network connection will drop and reconnect momentarily.

Step 7 — Test the fix

Verify DNS resolution is working correctly.

Run: nslookup luvvhelp.com or try loading a website that previously failed.

Common fixes by symptom

Some websites don't open

Likely causes:

Stale DNS record in local cache.
Website's DNS record recently changed.

Safe fixes:

Clear DNS cache as per guide.
Try using a public DNS like 8.8.8.8 temporarily.

Stop if: The site works on other devices—then it's a device-specific config.

DNS resolution fails entirely

Likely causes:

Misconfigured DNS server settings.
DNS caching service crashed.
Firewall blocking DNS port 53.

Safe fixes:

Restart the DNS caching service (nscd, dnsmasq).
Check /etc/resolv.conf for valid nameservers.

Stop if: You suspect firewall changes; incorrect edits can break connectivity.

Slow website loading initially

Likely causes:

DNS cache was empty, causing a fresh lookup.
Slow upstream DNS server.

Safe fixes:

Clearing cache might not help; this is often normal.
Configure faster DNS servers (e.g., Cloudflare 1.1.1.1).

Stop if: The slowness is consistent across all sites—then check overall internet speed.

Connected but no internet

Likely causes:

DHCP failure not providing DNS servers.
Router DNS issues.

Safe fixes:

Renew DHCP lease: sudo dhclient -r && sudo dhclient.
Set manual DNS in network settings as a test.

Stop if: Pinging IP addresses also fails; this is a broader network issue.

Quick reference

Network Metric	What It Means	Good Baseline
Latency (Ping)	Time for a data packet to travel to a server and back. Affects real-time apps.	< 50 ms (to a local server).
Jitter	Variation in latency. High jitter causes choppy voice/video.	< 10 ms.
Packet Loss	Percentage of data packets lost in transit. Causes skips and disconnections.	0% ideal, < 1% acceptable.
Throughput	Actual speed of data transfer. Often less than your plan's advertised speed.	≥ 80% of your subscribed plan.
Signal Strength (Wi-Fi)	Power of the Wi-Fi signal received by your device.	-50 dBm (excellent) to -70 dBm (fair).

Setting	Safe Baseline	Purpose
Wi-Fi Security	WPA2/WPA3 (AES).	Encrypts traffic, prevents unauthorized access.
DNS Servers	Router default, or public (1.1.1.1, 8.8.8.8).	Translates domain names to IP addresses.
Router Admin Access	Unique username & strong password.	Prevents unauthorized configuration changes.
Guest Network	Enabled with separate password.	Isolates guest devices from your main network.
Firmware Updates	Check every 3–6 months.	Patches security flaws and adds features.

Mind map summary

DNS Issue on Linux
|
├── Is it only this device?
│   ├── Yes → Proceed with local cache clear.
│   └── No → Restart router, check ISP.
|
├── Local Diagnosis
│   ├── Can ping IP? (8.8.8.8)
│   │   ├── Yes → DNS problem likely.
│   │   └── No → General network problem.
│   └── Can resolve domain? (nslookup)
│       ├── Yes → Cache may have a stale single entry.
│       └── No → DNS resolver failing.
|
├── Clear Cache
│   ├── Identify Service
│   │   ├── systemd-resolved → sudo systemd-resolve --flush-caches
│   │   ├── nscd → sudo systemctl restart nscd
│   │   ├── dnsmasq → sudo systemctl restart dnsmasq
│   │   └── Unknown/None → Restart NetworkManager
│   └── Test (nslookup)
|
└── If Problem Persists
    ├── Change DNS server settings (to 1.1.1.1).
    ├── Check firewall rules (port 53).
    ├── Renew DHCP lease.
    └── Escalate to router/ISP config.

Troubleshooting checklist

Device (Your Linux PC)

Clear local DNS cache (steps above).
Check /etc/resolv.conf for valid nameservers.
Renew DHCP lease with dhclient.
Disable VPN/proxy temporarily.
Test with a different DNS server.
Restart NetworkManager/service.

Router

Power cycle (unplug for 30 seconds).
Check router's DNS settings.
Update router firmware.
Disable router-level DNS filtering if enabled.

ISP & External

Check ISP status page for outages.
Test connection with ISP's default DNS.
Note if issue happens at specific times.
Contact ISP with detailed symptoms.

When to escalate

Contact your ISP if:
- DNS issues affect all devices on your network, even after a router reset.
- You consistently cannot resolve any domain names, but pinging IPs works.
- The problem coincides with a known service disruption in your area.
Consider replacing router/hardware if:
- Router settings reset frequently or firmware updates fail.
- Network problems are intermittent and correlate with router overheating.
- The router is very old (5+ years) and lacks security updates.
Ask IT support or a professional if:
- You are managing a business network or complex firewall rules.
- You suspect a deeper system configuration error you're not comfortable editing.

What to collect before escalating:

Results from speed tests and ping tests to multiple targets.
Timestamps of when the problem occurs.
Exact error messages from browser or terminal commands.
Your router model and firmware version.
Steps you have already tried.

FAQ

What is DNS cache and why does it need clearing?

DNS cache is a temporary database on your computer or router that stores recent translations of domain names (like luvvhelp.com) to IP addresses. It speeds up browsing by avoiding repeated lookups.

It needs clearing when the stored information becomes outdated or corrupted, which can cause websites to fail to load, redirect incorrectly, or show security certificate errors.

Is clearing DNS cache safe?

Yes, it is completely safe. It is a temporary, non-destructive operation. The worst that can happen is a slight delay the next time you visit a website as your system fetches fresh DNS records. No personal data or settings are deleted.

How often should I clear my DNS cache?

For most users, rarely or never. Modern systems manage cache well. Only clear it when you are actively troubleshooting a website loading issue or after changing network/DNS settings. It's not routine maintenance.

The commands didn't work. Does my Linux system have a DNS cache?

Not all Linux systems run a local DNS cache by default. Some lightweight distributions or desktop environments skip it to save resources. In these cases, your system queries your router or configured DNS servers directly. Use systemctl list-units | grep -E '(resolv|nscd|dnsmasq)' to check for services.

Will clearing DNS cache make my internet faster?

Usually not. If your cache was corrupted, it might resolve a specific slowdown for a previously problematic site. However, for general browsing, a populated cache is slightly faster because it avoids a lookup delay. Clearing it may cause a brief, one-time slowdown for fresh lookups.

What's the difference between clearing DNS cache and browser cache?

DNS cache is handled by your operating system or router and maps domain names to IP addresses. Browser cache stores website files (images, HTML, CSS) on your hard drive to load sites faster on revisit. They are separate. Clearing one does not affect the other.

Can I disable DNS caching on Linux?

Yes, you can disable the caching service (e.g., stop and disable systemd-resolved or nscd). However, this is not recommended for most users as it will increase the time it takes to initially connect to websites and place more load on your upstream DNS servers.

Do I need to reboot after clearing the cache?

No, a reboot is not necessary. The effect of clearing the DNS cache is immediate. If you restarted a service (like nscd), that service is already running with a fresh cache.

Sources and references

Linux manual pages (man pages) for systemd-resolve, nscd, dnsmasq, and dhclient.
systemd project documentation on systemd-resolved service and cache management.
Distributor-specific support documentation (Ubuntu, Fedora, Arch Wiki).
Networking diagnostics fundamentals (ICMP ping, DNS query tools like dig and nslookup).
IEEE 802.11 standards overview for understanding underlying Wi-Fi connectivity.
General DNS protocol RFCs explaining record types and caching mechanisms.
Router vendor generic administration guides for DNS configuration.

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