[SOLVED] Linux DNS Failure: 'Could not resolve host' / systemd-resolved

The systemic failure Temporary failure in name resolution, Could not resolve host: google.com or Failed to start Network Name Resolution in Linux occurs when the local domain resolver daemon or /etc/resolv.conf loses valid upstream nameserver configurations, halting outbound network connections requiring hostname resolution.

Step-by-Step Solution

1. 1

   Step 1: Restore Immediate Connectivity via Static Nameservers

   If your server cannot fetch packages due to missing nameservers, inject temporary fallback resolvers:

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   # Direct public Cloudflare and Google nameservers
   echo -e "nameserver 1.1.1.1\nnameserver 8.8.8.8" | sudo tee /etc/resolv.conf
   

   Verify connectivity:

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   ping -c 3 google.com
   

2. 2

   Step 2: Reconstruct Official systemd-resolved Symlink

   On modern Linux distributions, /etc/resolv.conf must link directly to the runtime stub resolver:

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   # 1. Remove broken symlink or stale file
   sudo rm -f /etc/resolv.conf
   
   # 2. Re-establish official stub symlink
   sudo ln -s /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
   
   # 3. Restart and enable resolver daemon
   sudo systemctl restart systemd-resolved
   sudo systemctl enable systemd-resolved
   

3. 3

   Step 3: Configure Upstream Resolvers in resolved.conf

   Open your master configuration file (/etc/systemd/resolved.conf):

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   [Resolve]
   DNS=1.1.1.1 8.8.8.8
   FallbackDNS=1.0.0.1 8.8.4.4
   Domains=~.
   DNSSEC=allow-downgrade
   

   Restart daemon to load new nameserver bindings:

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   sudo systemctl restart systemd-resolved
   

4. 4

   Step 4: Verify Resolution State with resolvectl

   Confirm that active network interfaces hold valid DNS assignments:

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   # Query active DNS resolver telemetry
   resolvectl status
   

❓ Frequently Asked Questions (FAQ)

Why does ping 8.8.8.8 succeed while ping google.com fails?

Because low-level IP routing is functional, but the Application layer hostname-to-IP translation (DNS) subsystem is offline.

What is the role of 127.0.0.53 in resolv.conf?

127.0.0.53 is the local stub listener managed by systemd-resolved to provide local caching and DNSSEC validation.