Wired Network Fix on Linux Mint 19.3

I recently decided to try Linux Mint 19.3 (Cinnamon) on an old Lenovo laptop, a G530 I’ve written about previously. The install went smoothly, but upon completion, it turned out that I had no network access whatsoever – neither wired nor wireless. The wireless is a Broadcom chip, so I kind of expected that. But the wired should have been supported.

Here’s the output of lspci | grep -i net:

04:00.0 Network controller: Broadcom Inc. and subsidiaries BCM4312 802.11b/g LP-PHY (rev 01)
07:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetLink BCM5906M Fast Ethernet PCI Express (rev 02)

Even with a wired connection plugged in, it would not show up in the NetworkManger window. I even tried creating a new connection, but this did not help. After running ifconfig, I found that the interface was in fact picked up. I was actually able to bring it up like this:

sudo dhclient enp7s0

In the above, enp7s0 is just my wired interface. Running ifconfig again I could see that it now had an IP, and I was able to ping other hosts, run updates, and even use the Driver Manager to install drivers for the wireless card, which promptly started working. For whatever reason, NetworkManager was not configuring the wired connection.

It turns out that during install, this interface was added to /etc/network/interfaces, which makes NetworkManager ignore it. All I had to do was modify this file as follows:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

# These next two lines refer to the wired network card.  They
# should be commented out.
#auto enp7s0
#iface enp7s0 inet manual

Then, I was able to run sudo systemctl restart NetworkManager and the connection started showing up in the system tray.

This is a little annoying, and I would think it’s something that could have been picked up during install, but at least it’s easy enough to fix. This is my first real experience working with Mint, and overall it seems very polished, this issue aside.