Ubuntu 20.04 Grub replaced by Debian Grub and the VM does not connect to the network

[exsurgo-ankit]

Hello,

I am running Ubuntu 20.04 on a virtual machine hosted on VirtualBox software in Windows 10. Things were fine for a few months since install, then in the last couple days after a power outage, the system only shows Debian Grub options.
It only boots into Xfce UI. I can still login as the main user and I checked that all my files exist. But there is no network.

I tried booting with a live CD, and the networking works in a live session.

I have tried running the Boot Repair but get an error - "The system is in Bios-compatibilty mode...."

Here is a pastebin link to the boot info
https://paste.ubuntu.com/p/xMg8MjCrdj/

I am lost as to how I can revert back to the Ubuntu desktop where all my services were accessible and the networking was working.

I have spent a few hours googling this and none of the suggestions have worked. I have tired modifying grub.cfg, running boot-repair.
The closest explanation similar to the issue I found in at this link but it has no solution.
https://unix.stackexchange.com/quest...-default-os-to

Any pointers to get this resolved will be greatly appreciated.

Regards

[slickymaster]

Thread moved to Virtualisation for a better fit

[MAFoElffen]

Sorry for no response before this. I saw one post, and thought it had been addressed. I just noticed it had been moved from somewhere else.

So let's see where you are at. You say you installed clean/fresh with Ubuntu 20.04 a few months ago, as a Virtual box VM on a Windows 10 host. So it was not an upgrade from another release version, and it was installed as a Ubuntu Desktop... You now, after a power outage, have a problem with the desktop and with network settings... Is that about right?

My curiosities:
That you said you can start an Xfce desktop environment, that the Grub Menu changed from the Ubuntu Branding to some kind of Debian Branding. I was not aware that the Xfce desktop was installed on a vanilla install of Ubuntu. The same with the Debian branding of the Grub2 package. Both of those would take additional steps to get there. Is there something more or anything else you would like to add of packages you added after the installed? After the install and initial configuration, did you not take a snapshot to fall back to? (just something to think about in your practices).

Next, that with a power failure, was the VM running when the power (not powered down) was interrupted? If so, then the state file was corrupted. Again, in hindsight, if you used:

VBoxManage discardstate "vm_name"

... before you tried to reconnect to that VM, then it would have started clean from a fresh boot. You might still try that... I would. No harm right?

On the VM networking, did you configure networking on the VM after the install? For instance, the VM switch is working fine. You said you attached a LiveCD ISO to it and it booted fine and had networking. So default DHCP works on that VM.

So with 20.04, the default networking is NetPlan. Using the LiveCD environment, look at the file at /etc/netplan/01-network-manager-all.yaml and post the contents of that in a post wrapped within code tags.

I wrote it 10 years ago, but in the sticky in my signature line, in post #3, is a tutorial for using a LiveCD environment to mount an installed system. After doing that, you can diagnose that system, install and/or make changes to it, as if it had booted... Just saying that you don't have to start over. But that is an option also.

You could just use the LiveCD environment to copy what you need to an USB drive or USB storage, export a installed package list to help you install what you installed after vanilla, and just start fresh. Your decision. Your investment in time.

I learned long ago, from mistakes and heart break. Use snap shots and backups.

[exsurgo-ankit]

Hello MAFoElffen

Thank you for getting back to me. Yes I did take a snapshot but it is over a couple months old. That would be my last resort, if I can't recover this instance.
What I don't understand is how I could have overwritten the UI and affected the networking. I did try running some updates as I working on setting up some plugins for jenkins.

Is there a way to revert those installations?
I can work with the Debian GUI as well if the networking worked. Without networking this image will be useless to us. What can I try to get the networking to work?

I have tried mounting the local file system as per your suggestion but I can unable to run any apt-get commands. The live system is unable to resolve network addresses for packages.
I tried switching the user from root@ubuntu to my local admin@ubuntu.
All my folders and data are intact.

I will provide an update if something works out. Please provide any suggestions to get the networking working.

[MAFoElffen]

First would be to re-establish the networking on that image while mounted to it (easiest)... While mounted to it, does it lose the networking again?

*** You never did answer if you knew if it was using NetPlan or Network Manager to render the the networking(?) ***
If so, then you coudld use the configured (mounted) network manager renderer to reconfigure your network settings... (hint)

Later, after a resolved network connection, then you could re-install the Desktop, which would correct anything there that got wacked. But before doing that, I would try to fix any errors on the system, disk errors, any broken packages, and such. Instructions for that later...

[exsurgo-ankit]

Hello MAFoElffen,

I am googling netplan so I can try your suggestion. Networking did not work when I mounted the local file system. No apt-get commands could resolve the host.

On Debian boot, the icon says Xubuntu. Did it somehow update to Xubuntu? I am not sure how I did that.
When is shows the login prompt, it momentarily shows the ubuntu background and switches to xfce background.
Logging in as other user (my admin) still shows xfce desktop with no networking.

Regards

[MAFoElffen]

Did you install any "alternate" desktops to your Ubuntu image? What "Graphical Login Manager" is it using now?

If not GDM (the Ubuntu default) currently, then do:

sudo dpkg-reconfigure gdm3

To set your default desktop environment back to Ubuntu, do:

sudo update-alternatives --config x-session-manager

* Curious to hear what desktops it says is there.

On 20.04, post the contents of /etc/netplan/01-<file_name>.yaml. that will show what the renderer is.

[exsurgo-ankit]

I did not install any alternate desktops. It is using xfce. I probably ran apt upgrade before the power outage and that may have triggered this state.
It did not work. Here are the outputs

gdm3 is broken or not fully installed.

for the second command it says
no alternatives for x-session-manager

[MAFoElffen]

And yet, you still have not posted your *.yaml file... I can not help you restore your network settings until provide that information. And answer the network related questions I asked above. I am sorry, but I have asked for that multiple times.

You cannot fix it until, well... I am in the dark until you can provide some info. I'm waiting on you. I am patient.

[exsurgo-ankit]

Hello MAFoElffen,

Apologies for the misunderstanding. I am a noob when it comes to Linux. I did not setup any networking. The VM is bridged to the host PC's network adapter.
It just worked seamlessly. It still does with the live session from the install DVD.

There is a single file called 01-network-manager-all.yaml



it has 4 lines that look like this

# Let NetworkManager manage all devices on this system
network:
version:2
renderer: NetworkManager