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Rename WiFi Interface on Ubuntu 20.04

Junxiao Shi
stallion coder; push-up specialist
Originally published at yoursunny.com ・2 min read

This post is originally published on yoursunny.com blog https://yoursunny.com/t/2021/WiFi-rename/

During an experiment, I need to use three WiFi interfaces on a Raspberry Pi running Ubuntu 20.04.
In addition to Raspberry Pi's internal WiFi interface, I added two USB WiFi adapters.
Three network interfaces showed up in the system (ip link command), and they are named wlan0, wlan1, and wlan2 by default.

I often need to capture packets with tcpdump, and I often have to be type these interface names manually.
It isn't easy to remember the purpose of each network interface, so I wanted to rename the interfaces to reflect their role in my application.
However, this isn't as easy as it sounds.

🚫 Netplan

Ubuntu 20.04 configures network interfaces using Netplan, so my first thought was: I can write a Netplan configuration that matches network interfaces with their MAC addresses, and assigns the desired name to each network interface.

The config file would look like this:

network:
  version: 2
  wifis:
    uplink:
      optional: true
      match:
        macaddress: ba:fe:de:f0:b9:e4
      set-name: uplink
      access-points:
        home:
          password: rP8jKHJ64
      dhcp4: true
      dhcp6: true
      accept-ra: true
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However, this method would not work:

$ sudo netplan apply
ERROR: uplink: networkd backend does not support wifi with match:, only by interface name
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🚫 70-persistent-net.rules

Many online guides refer to a file /etc/udev/rules.d/70-persistent-net.rules, which is processed by udev during boot.
The file should have been created automatically by the system upon discovery of the network interfaces, and I just need to modify the interface names to the desired names.

However, this file does not exist in Ubuntu 20.04, so it's another dead end.

✔️ systemd.link

After carefully reading Debian's NetworkInterfaceNames guide, I found the correct way: systemd.link.

To rename WiFi interfaces, I can create a systemd configuration file for each network interface:

echo '[Match]
MACAddress=ba:fe:de:f0:b9:e4
[Link]
Name=uplink' | sudo tee /etc/systemd/network/10-uplink.link
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After rebooting, the network interface is renamed to what I wanted.

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