How to get eth0 and wlan0 back on Ubuntu Mate 18.04?

[Tom H]

On Sun, Jan 31, 2021 at 8:39 AM Bo Berglund <bo.berglund at gmail.com>
wrote:


> When I got back into this I found that the next steps after
> editing grub according to my notes is:

I assume that you mean "editing /etc/default/grub" when you say "editing grub."


> sudo grub-mkconfig -o /boot/grub/grub.cfg

On Ubuntu, this is the same as "update-grub".


> and then:
> sudo nano /etc/network/interfaces
>
> Here the file is supposed to be modified by setting it thus:
>
> auto eth0
> iface eth0 inet dhcp
>
> However nothing is said about wlan0 in my notes and my existing file looks like
> this:
>
> # interfaces(5) file used by ifup(8) and ifdown(8)
> auto lo
> iface lo inet loopback
>
> Should I change it to become like this:
>
> # interfaces(5) file used by ifup(8) and ifdown(8)
> auto lo
> iface lo inet loopback
>
> auto eth0
> iface eth0 inet dhcp
>
> auto wlan0
> iface wlan0 inet dhcp
>
> I.e. just add the two new names onto the end of the file?
>
> I have not yet made any of the changes because currently the laptop is using
> wifi and I access it via PuTTY ssh (and VNC) so I need to make sure I do not
> break any networking before I finalize the changes and reboot.

Since you installed "ifupdown" after your network was set up,
netplan's setting it up.

If you're using wifi (and I assume wpa), you'll need to change the
wlan0 stanza to include the ssid and password:

allow-auto wlan0
iface wlan0 inet dhcp
    wpa-ssid SSID
    wpa-psk PASSWORD

and then move "/etc/netplan/*.yaml" out before rebooting.