How to configure network in Ubuntu 18.04 and derivatives

As you may have noticed, the network configuration in Ubuntu 18.04 has changed. /etc/network/interfaces is not used anymore.
We’ll see how to configure network interfaces from command line in Ubuntu 18.04 and derivatives.
This is what we will learn:

• Netplan tool and configuration files.
• Modify configuration yaml file, a few examples.
• Apply modified network settings.

This article applies to network configuration through networkd, which is going to be specially usefull for command line setup.
If you are on a desktop environment, you probably have network-manager installed, so just config your network interfaces using the network graphic tool.

Netplan tool and configuration files

The tool we have to use now is “netplan”.
This tools uses a different network configuration files, the new files are under /etc/netplan, there you can find a “YAML” file.
If there are no files there, or you need to create them, you can generate them with:

netplan generate

Modifying configuration yaml file, a few examples

This is how my VM test config file /etc/netplan/01-netcfg.yaml looks like:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: yes
    enp0s8:
      dhcp4: no
      dhcp6: no
      addresses: [192.168.56.23/24]

We can easily find the patern here.
Lets see 2 typical examples.

Static IP with gateway and DNS

In this example, IP:192.168.56.23 and netmask 255.255.255.0, gateway:192.168.56.1 and DNS servers:192.168.56.1 and 8.8.8.8.

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: no
      dhcp6: no
      addresses: [192.168.56.23/24]
      gateway4: 192.168.56.1
      nameservers:
        addresses: [192.168.56.1,8.8.8.8]

Dynamic IP – DHCP

Automatic config with DHCP:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
	  dhcp4: yes

Applying modified network settings

There are two ways to do this: using netplan tool or restarting networkd daemon.

Using Netplan

sudo netplan apply

Restarting networkd daemon

systemctl status systemd-networkd