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URL: https://linuxconfig.org/how-to-switch-back-networking-to-etc-network-interfaces-on-ubuntu-20-04-focal-fossa-linux

⇱ Switch Networking to /etc/network/interfaces Ubuntu

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This article will explain how to switch back networking from NetPlan/CloudInit on Ubuntu 20.04 Focal Fossa Linux to yet now already obsolete networking managed via /etc/network/interfaces.

In this tutorial you will learn:

  • How to revert to eth0..n network naming convention
  • How to install ifupdown
  • How to remove CloudInit
  • How to enable networking daemon
👁 How to switch back networking to /etc/network/interfaces on Ubuntu 20.04 Focal Fossa Linux
How to switch back networking to /etc/network/interfaces on Ubuntu 20.04 Focal Fossa Linux

Software Requirements and Conventions Used

Software Requirements and Linux Command Line Conventions
Category Requirements, Conventions or Software Version Used
System Installed Ubuntu 20.04 or upgraded Ubuntu 20.04 Focal Fossa
Software N/A
Other Privileged access to your Linux system as root or via the sudo command.
Conventions # – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
$ – requires given linux commands to be executed as a regular non-privileged user

How to switch back networking to /etc/network/interfaces on Ubuntu 20.04 step by step instructions

  1. First step is to install tools to configure network interfaces 
    $ sudo apt update
$ sudo apt install ifupdown net-tools
  2. Next, change from current enp0s3 to old network interfaces naming convention eth0. To do so with administrative privileges edit the /etc/default/grub file anf change the following line: 
    FROM:
GRUB_CMDLINE_LINUX=""
TO:
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"
    👁 old network interfaces naming convention eth0
    Edit Grub boot to change to old network interfaces naming convention eg. eth0

    Once ready update Grub with:

    $ sudo update-grub
  3. Reboot your system: 
    $ sudo reboot
  4. As root or any administrative user edit the /etc/network/interfaces file and set eth0 network interface to obtain the IP address from DHCP: 
    source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

    Check this article if you need to set your network interface to a static IP address.

  5. Restart eth0 interface: 
    $ sudo ifdown --force eth0
$ sudo ifup eth0
  6. At this stage you should have your eth0 configured. Use ifconfig command to check the networking interface configuration: 
    ifconfig 
eth0: flags=4163
  7. First disable and stop Configure DNS resolution to eg. 8.8.8.8 nameserver: 
    $ sudo unlink /etc/resolv.conf
$ sudo echo nameserver 8.8.8.8 >> /etc/resolv.conf
  8. Let’s perform soul cleanup. Remove cloud init package: 
    $ sudo dpkg -P cloud-init
$ sudo rm -fr /etc/cloud/

    Disable and stop systemd-resolved service:

    $ sudo systemctl disable --now systemd-resolved