Ubuntu Server 20.04 no internet connection/network unclaimed

Question

I tried installing Ubuntu Server 20.04 on my Gigabyte B550i with an Realtek Ethernet Controller and wireless. I want to use ethernet (I don't care about wireless), but I wasn't able to set it up during installation and cat /etc/netplan.*yaml returns just:

network:
      version 2

and lshw -C network lists both networks, the ethernet one unclaimed, the wireless one diabled. /etc/network/interfaces is empty, I tried different file contents, but nothing worked.

What am I doing wrong? I tried installing some kind of drivers, but didn't succeed.

EDIT

ip a returns

1: lo: <LOOPBACK,UP, LOWER_UP> mtu 65536 qdisc noqeue state UNKOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preffered_lft forever
    inet6 ::1/128 scope ost
        valid_lft forever preferred_lft forever
2: wlp6s0 <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 34:cf:f6:b7:d4:8c brd ff:ff:ff:ff:ff:ff:ff

EDIT 2 Images

lshw -C network

lspci -k

Answer 1

Your netplan .yaml file is broken.

ls -al /etc/netplan # get .yaml filename

sudo lshw -C network # identify ethernet device name, enxxxxxx

Edit it with:

sudo pico /etc/netplan/*.yaml <-- change the * to your filename

Initially make its content the following, with EXACLY the same spacing, indentation, and no tabs:

network:
  version: 2
  renderer: networkd
  ethernets:
    en01:
      dhcp4: true
      dhcp6: true
      optional: true
  wifis:
    wlp6s0:
      dhcp4: true
      dhcp6: true
      access-points:
        "YourWifiNetworkName":
          password: "WifiNetworkPassword"

sudo netplan generate

sudo netplan apply

reboot

Update #1:

BIOS

You have BIOS version F1.

The current BIOS is version F2a, dated 6/16/2020, and can be downloaded here.

Note: Confirm that I have the correct web page for your motherboard model #.

Note: Have good backup before updating the BIOS.

kernel

With the newer ethernet controller that you have, you may need to run with a newer kernel than stock from Ubuntu 20.04.1.

Go here to download the latest 5.8.3 kernel. Get the 4 regular .deb files, not the lowlatency files.

Update #2:

Word is that not even kernel 5.8.3 supports the RTL8125! Kernel 5.9 is supposed to support it, but there is only a 5.9-rc2 (rc2 means release candidate #2) version available now... see https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.9-rc2/.

In the mean time, download this Linux driver from Realtek, and it should work. https://www.realtek.com/en/component/zoo/category/network-interface-controllers-10-100-1000m-gigabit-ethernet-pci-express-software. Get the one for "2.5G Ethernet LINUX driver r8125 for kernel up to 5.6"... and use your original 5.4.x kernel.

Update #3:

Ordered a $13 TP-Link USB 3.0 Ethernet dongle to be able to connect and download/install required Ubuntu packages. https://www.amazon.com/dp/B00YUU3KC6

Update #4:

Installed USB to Ethernet adapter. Installed build-essential. Built driver. Everything works. Wireless will be completed when the need arises. Will need to install wpasupplicant.

Answer 2

You can try configuring this for Wifi but it'll require you to do some more work.

Your wifi device is: wlp6s0

Try this netplan configuration in place of whatever you currently have (AND MAKE SURE YOU MATCH SPACING!), then run sudo netplan test and reboot the server after:

network:
  version: 2
  renderer: networkd
  wifis:
    wlp6s0:
      dhcp4: yes
      dhcp6: yes
      access-points:
        "YourWifiNetworkName":
          password: "WifiNetworkPassword"

Replace YourWifiNetworkName and WifiNetworkPassword accordingly to manually set the wifi network and its connection authentication password that your server will connect to. You do need the quotes around those two arguments, as shown in the Netplan Examples and the exact example I referenced.

Answer 3

I solved it by pulling out my bios/uefi battery for several minutes and it worked like a charm! It happened twice and I solved it twice this way. I did everything listed here and more but it didn't solved my problem. I didn't touch bios/uefi settings before. This is not a joke. I got the same problem with intel network adapter on Ubuntu 20.04. Terminal lshw listed my adapter as UNCLAIMED. I tried every page with the same problem but it didn't solved this issue.