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

[Ralf Mardorf]

On Wed, 27 Jan 2021 11:36:23 +0100, Bo Berglund wrote:
>On Wed, 27 Jan 2021 10:35:30 +0100, Ralf Mardorf via ubuntu-users
><ubuntu-users at lists.ubuntu.com> wrote:
>
>>On Wed, 27 Jan 2021 10:18:06 +0100, Bo Berglund wrote:  
>>>But the first part of this instruction is not clear since it says to
>>>"add" to /etc/default/grub like this:  
>>
>>Hi,
>>
>>I can't speak for other languages, but related to
>>https://www.dict.cc/?s=add , the translation of the English word "add"
>>to German is unambiguous.
>>
>>If you "add" (as I understand it)
>>
>>net.ifnames=0 biosdevname=0
>>
>>to
>>
>>GRUB_CMDLINE_LINUX="resume=UUID=<long guid string>"
>>
>>the result is
>>
>>GRUB_CMDLINE_LINUX="resume=UUID=<long guid string> net.ifnames=0
>>biosdevname=0"
>>  
>
>Yes, semantically speaking it is like that or it could also be like
>this:
>
>GRUB_CMDLINE_LINUX="resume=UUID=<long guid string>" "net.ifnames=0
>biosdevname=0"
>
>So since there are quotes around what is proposed to be put into
>GRUB_CMDLINE_LINUX and the proposed entry looks like 2 separate
>commands, should then the added command just be stuffed inside the
>existing quote or inside a separated quoted entry in order to be
>"added". Quite often when one has other commands with arguments and
>these contain spaces one uses quotes to package the whole string as
>one argument so it does not get split.
>But in this case it looks problematic since the proposed argument does
>contain a space and this could be the reason for the quote around it...
>
>I don't want to brick the laptop because of an error here (since if
>GRUB fails I suspect Ubuntu won't even start up...

I don't think so.

1. resume=UUID=<long guid string>
   doesn't contain any spaces, assuming <long guid string> is actually
   replaced by a real UUID.

2. net.ifnames=0 biosdevname=0
   are to separated things, it's not one "command". If you should be
   right, it would be wrong to put both in the same quotes. And it
   actually seems to be like that, see hint at the bottom.

https://wiki.debian.org/NetworkInterfaceNames
https://en.wikipedia.org/wiki/Consistent_Network_Device_Naming

I'm using Syslinux and would add those parameters with no quotes at
all to the real config. Before I migrated to Syslinux, I edited
grub.cfg directly.

A Syslinux example with other parameters:

[weremouse at moonstudio ~]$ grep "LABEL Moonstudio" /mnt/archlinux/boot/syslinux/syslinux.cfg -A5 | tail -12
LABEL Moonstudio
    MENU LABEL Ubuntu X ^Moon Studio lowlatency
    LINUX /.boot/ubuntu_moonstudio/boot/vmlinuz-lowlatency
    APPEND root=LABEL=moonstudio ro
    INITRD /.boot/ubuntu_moonstudio/boot/initrd.img-lowlatency

LABEL Moonstudio_no_mitigations
    MENU LABEL Ubuntu X Moon Studio lowlatency          no miti^gations
    LINUX /.boot/ubuntu_moonstudio/boot/vmlinuz-lowlatency
    APPEND root=LABEL=moonstudio ro noibrs noibpb nopti nospectre_v2 nospectre_v1 l1tf=off nospec_store_bypass_disable no_stf_barrier mds=off mitigations=off audit=off
    INITRD /.boot/ubuntu_moonstudio/boot/initrd.img-lowlatency

Keep in mind that Grub hast got a config for a config. You probably
should forget about common sense, POSIX and Co. If you are
uncertain, consider to read the Grub manual.

"The file /etc/default/grub controls the operation of grub-mkconfig. It
is sourced by a shell script, and so must be valid POSIX shell input;
normally, it will just be a sequence of ‘KEY=value’ lines, but if the
value contains spaces or other special characters then it must be
quoted. For example:

GRUB_TERMINAL_INPUT="console serial"" -
https://www.gnu.org/software/grub/manual/grub/html_node/Simple-configuration.html

If so, then

GRUB_CMDLINE_LINUX=resume=UUID=<long guid string> net.ifnames=0 iosdevname=0

with no quotes at all, should do the trick.

Note, I didn't read the complete manual and might be missing something.