How to Fix the “sudo systemd-resolved command not found error Ubuntu”

Encountering the error “sudo systemd-resolved command not found error Ubuntu” indicates that your system cannot locate the systemd-resolved executable within your PATH.

This guide provides a structured approach to troubleshoot and resolve the issue efficiently.

Understanding the Issue

When you execute a command using sudo, Ubuntu searches the directories specified in the PATH environment variable. If it fails to find systemd-resolved, the error appears. This may stem from misconfiguration, installation problems, or using an alternative DNS resolver.

Read: How to Troubleshoot and Optimize Ubuntu Startup: Manage Systemd Services for Faster Boot Time

Common Causes and Their Solutions

1. Missing or Misconfigured systemd-resolved

Explanation:
The systemd-resolved service, a component of the systemd suite, handles DNS resolution on Ubuntu. In minimal or customized installations—or if an installation error occurred—this service might be absent or misconfigured.

Solution:

• Update Package Lists:
  Refresh your package data:

  sudo apt update
  

• Reinstall systemd:
  Reinstalling systemd reinstates all its components:

  sudo apt install --reinstall systemd
  

• Verify the Installation:
  Confirm that systemd-resolved exists by checking its path:

  which systemd-resolved
  

  A returned path (commonly /usr/lib/systemd/systemd-resolved or /usr/bin/systemd-resolved) indicates a proper installation.

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2. PATH Environment Variable Misconfiguration

Explanation:
Although uncommon, the directory containing systemd-resolved might not be listed in your PATH.

Solution:

• Check Your PATH:
  Display the current PATH variable:

  echo $PATH
  

• Locate the Binary:
  Identify the binary location:

  whereis systemd-resolved
  

  If the directory (e.g., /usr/lib/systemd or /usr/bin) isn’t part of your PATH, temporarily add it:

  export PATH=$PATH:/usr/lib/systemd  # Adjust based on the actual location
  

Note: This is a temporary fix for testing; a persistent issue may require revisiting your shell configuration files.

Read: How to analyze Linux systemd logs using journalctl advanced filtering options

3. Typographical Errors in the Command

Explanation:
Simple typos can trigger the error.

Solution:
Double-check and retype the command accurately:

sudo systemd-resolved --flush-caches

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4. Alternative DNS Resolver Configuration

Explanation:
Some systems use a different DNS resolver (e.g., dnsmasq, unbound, nscd, bind9), meaning systemd-resolved may not be in use.

Solution:

• Verify Service Status:
  Check if systemd-resolved is active:

  systemctl status systemd-resolved.service
  

• Flush DNS Cache for Alternative Resolvers:
  Depending on your setup, you might need to restart another service:
  • dnsmasq:

    sudo systemctl restart dnsmasq
    

  • nscd:

    sudo systemctl restart nscd
    

    or

    sudo /etc/init.d/nscd restart
    

  • bind9:
    Refer to your server’s documentation for cache flushing instructions.

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Step-by-Step Troubleshooting Summary

1. Refresh Your Package Lists:

   sudo apt update
   

2. Reinstall the systemd Package:

   sudo apt install --reinstall systemd
   

3. Verify the Installation:
   Use:

   which systemd-resolved
   

   to confirm a valid path is returned.

4. Check the Service Status:

   systemctl status systemd-resolved.service
   

5. Confirm Your DNS Resolver Setup:
   If the service is absent, investigate alternative DNS resolvers and use their specific cache flush methods.

Following these recommendations, you can swiftly resolve the “sudo systemd-resolved command not found error Ubuntu” and restore proper DNS functionality. This Ubuntu systemd-resolved troubleshooting guide is designed to streamline your process and ensure a stable system environment.

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