Software⏱️ 3 min read📅 2026-06-19

How to Fix: Why k3s install failed? Job for k3s.service failed because the control process exited with error code

Failed k3s installation on Ubuntu 22.04 due to control process exiting with error code.

Quick Answer: The issue is likely caused by a flannel backend configuration error. Try setting the `FLANNEL_BACKEND` environment variable to `flannel` instead of `none` during installation.

📋 Table of Contents

  1. 🔍 Why This Happens
  2. 🚀 How to Resolve This Issue
  3. ✨ Wrapping Up

The k3s installation failed on Ubuntu 22.04, resulting in a control process that exited with an error code. This issue affects anyone who has attempted to install k3s on this specific operating system.

This frustrating error can be resolved by following the steps outlined below. The primary goal is to troubleshoot and resolve the issue caused by the failed control process.

🔍 Why This Happens

  • The most common reason for this error is a misconfigured or missing network configuration, which prevents k3s from establishing a connection with other nodes in the cluster. This can happen if the `nm-cloud-setup.service` is not enabled or if there are issues with the network interface configuration.
  • Another potential cause is a problem with the `br_netfilter` and `overlay` kernel modules, which are required for k3s to function properly. If these modules are not loaded correctly, it can prevent k3s from starting.

🚀 How to Resolve This Issue

Troubleshooting Network Configuration

  1. Step 1: Check the network configuration to ensure that `nm-cloud-setup.service` is enabled and running.
  2. Step 2: Verify that the network interface configuration is correct and that there are no issues with IP addresses or subnet masks.
  3. Step 3: If necessary, update the network configuration using the `nmcli` command or edit the `/etc/netplan/00-netcfg.yaml` file to fix any errors.

Verifying Kernel Modules

  1. Step 1: Check if the `br_netfilter` and `overlay` kernel modules are loaded correctly by running the command `lsmod | grep br_netfilter` and `lsmod | grep overlay`.
  2. Step 2: If either of these modules is not loaded, try loading them using the `modprobe` command: `sudo modprobe br_netfilter` and `sudo modprobe overlay`. If these commands fail, you may need to modify your kernel configuration or seek additional assistance.

✨ Wrapping Up

To resolve the k3s installation issue on Ubuntu 22.04, follow the steps outlined in this guide. By troubleshooting the network configuration and verifying that the required kernel modules are loaded correctly, you should be able to successfully start the k3s service.

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