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Ubuntu Server Static IP (Netplan)

📌 Overview

When configuring Ubuntu Server, you may encounter an issue where the Static IP Address reverts to DHCP after a reboot. This problem is common in both Virtual Machines (VMs) (e.g., Proxmox, VirtualBox, VMware) and bare-metal servers.

This guide will help you troubleshoot and resolve this issue by properly configuring your network settings and disabling any conflicting services like cloud-init.

🔍 Understanding the Issue

⚠️ Cause

By default, Ubuntu Server uses cloud-init to manage network settings dynamically. While this is helpful in cloud environments, it can override manual network configurations, causing:

  • ❌ Static IP changes to DHCP after reboot
  • ❌ Netplan configuration files being ignored or overwritten
  • ❌ Inconsistent networking behavior

🔄 Effect

If not resolved, this can result in:

  • 🔗 Loss of network connectivity after reboot
  • 🌍 Difficulty accessing the server remotely
  • 🛑 Conflicts in network infrastructure when multiple devices receive unintended DHCP addresses

✅ Solution

To permanently set a Static IP, we will:

  1. Disable cloud-init (to prevent automatic configuration changes)
  2. Manually configure the network using Netplan
  3. Apply and verify the changes

1. Disable Cloud-Init

Cloud-init manages the default network configuration, but it often interferes with manual settings. To disable it:

sudo touch /etc/cloud/cloud-init.disabled

Then, remove any existing network configuration files created by cloud-init:

sudo rm -rf /etc/netplan/50-cloud-init.yaml

Disable the cloud-init service:

sudo systemctl disable --now cloud-init

(Optional) If you want to completely remove cloud-init:

sudo apt purge cloud-init -y

2. Manually Configure a Static IP

Now that cloud-init is disabled, we can manually set up Netplan.

Step 1: Identify the Network Interface

Run the following command to find your active network interface:

ip link show

You will see output like this:

2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000

Take note of the interface name (e.g., enp0s3), as we will use it in the next step.

Step 2: Create a Static IP Configuration

Create a new Netplan configuration file:

sudo nano /etc/netplan/50-static-ip.yaml

Add the following configuration (adjusting based on your network setup):

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3: # Change this to your actual network interface
      addresses:
        - 192.168.1.100/24
      routes:
        - to: default
          via: 192.168.1.1
      nameservers:
        addresses:
          - 8.8.8.8
          - 8.8.4.4
      dhcp4: no

Save the file (Ctrl + X → Y → Enter).

Ensure the file has the correct permissions:

sudo chmod 0600 /etc/netplan/50-static-ip.yaml

3. Apply and Verify Configuration

After setting up the static IP, apply the changes:

sudo netplan generate
sudo netplan try

If everything looks good, make it permanent:

sudo netplan apply

Reboot the server:

sudo reboot

After rebooting, confirm the Static IP is applied:

ip a

🛠️ Troubleshooting & Additional Tips

a. Verify the Correct Network Interface

If your changes do not take effect, ensure the correct interface is being used:

ip link show

Update your Netplan configuration with the correct name.

b. Check Netplan for Errors

Run this command to validate your Netplan configuration:

sudo netplan try

If an error appears, double-check your YAML syntax.

c. Confirm DHCP is Disabled

Check if your interface is still requesting DHCP:

journalctl -u systemd-networkd --no-pager | grep -i 'dhcp'

If DHCP is still active, ensure that dhcp4 is set to no in your Netplan file.

📌 Conclusion

By following these steps, you can ensure that your Ubuntu Server retains a Static IP Address across reboots, whether running on a Virtual Machine (VM) or bare-metal hardware.

✅ Summary of Key Steps:

✔️ Disable cloud-init to prevent conflicts ✔️ Manually configure Netplan with a static IP ✔️ Apply changes and verify the setup ✔️ Troubleshoot if necessary

Now your Ubuntu Server should maintain its network configuration consistently!

📚 References