Idantifying the Correct Configuration Path

Ubuntu's approach to static IP configuration diverges at the 17.10 release. First, confirm your release with lsb_release -r. The following procedures cover both modern and legacy setups.

Current Systems: Ubuntu 17.10 and Later (Netplan)

Netplan abstracts network configuration through YAML files. Locate your system's definition file:

ls /etc/netplan/

The output often shows a single file such as 01-network-manager-all.yaml or 00-installer-config.yaml. If multiple files exist, numerical prefix determines processing order.

Open the file for editing. Configure a static address by replacing the adapter block. The snippet below assumes the interface name is enp0s3; retrieve the actual name with ip link show.

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      addresses:
        - 10.0.2.15/24
      routes:
        - to: default
          via: 10.0.2.1
      nameservers:
        search: [localdomain]
        addresses: [9.9.9.9, 149.112.112.112]

Activate the new settings immediately:

sudo netplan apply

Should the adapter name not match, the apply step will fail. Use sudo netplan --debug apply to see detailed logs before troubleshoooting.

Legacy Distributions: Ubuntu 17.04 and Earlier (ifupdown)

For systems still relying on /etc/network/interfaces, define the static asssignment directly.

sudo nano /etc/network/interfaces

Populate it with a stanza similar to:

auto enp0s3
iface enp0s3 inet static
  address 10.0.2.15
  netmask 255.255.255.0
  gateway 10.0.2.1
  dns-nameservers 9.9.9.9 149.112.112.112

Restart the networking stack afterward:

sudo systemctl restart networking

Alternatively, cycle only the target interface:

sudo ifdown enp0s3 && sudo ifup enp0s3

Post-Configuration Verification

Validate that the adapter picked up the intended properties:

ip -brief address show enp0s3

Check Layer-3 reachability and name resolution:

ping -c 4 9.9.9.9
ping -c 4 10.0.2.1
host example.com

Safe Configuration Practices

• Back up before editing. For Netplan:

  sudo cp /etc/netplan/01-network-manager-all.yaml ~/netplan-backup.yaml
  

  For ifupdown:

  sudo cp /etc/network/interfaces ~/interfaces.backup
  

• Whitespace matters in YAML. Only spaces, never tabs, should be used for indentation within Netplan files.

• Address collision risk. Verify the chosen static IP is outside any DHCP pool and not assigned to another host. Use ping or arp-scan beforehand.