Troubleshooting - LXC TTY Terminal Login Prompt Shows Gibberish

[Wolveraptor]

Hello Proxmox Community,

I have encountered a weird issue that has been present for a while. The issue does not affect the usability of the LXC it is a mere annoyance. It happened when I upgraded from Fedora 42 within an LXC to Fedora 43 within an LXC. Since this has not hindered/impacted the LXC I did retain a backup prior to the upgrade form Fedora 42 to Fedora 43. The upgrade form Fedora 42 to Fedora 43 within the LXC was performed 1-2 months ago. Again, this isn't impacting production, just a minor annoyance to see the gibberish in the login field.

My Google-fu has not yielded fruit in coming to a solution.

The below screenshot shows the login prompt when using TTY that the login prompt is filled with gibberish.



When the gibberish occurs when using TTY, I can backspace up to, see below screenshot, enter my username and login. There is still some gibberish present.



This same gibberish does not occur prepopulated when changing the TTY setting from tty to /dev/console.



Any insight/ideas/help is appreciated if there is additional information required, I am happy to provide it. This was not happening prior to the upgrade from Fedora 42 to Fedora 43.

My PVE version is: pve-manager/9.1.1/42db4a6cf33dac83 (running kernel: 6.17.2-1-pve)

 

[kobe_highlander]

Sorry, no answer but seeing the same thing on my Proxmox installation. Saw it on Proxmox 8 and now on 9.1.4 as well. I have a feeling that 42-->43 is not working properly and staying on 42 for the time being (I had some other issues and reverted back to 42). Distro Upgrades worked till 42.

Like you, I can't find anything else on the net re/this topic.

 

[Wolveraptor]

No need to apologize, I am glad I am not alone.

I haven't been able to find a fix or workaround and like you, I have reverted back to Fedora 42. I ran Ubuntu LXCs prior to this and their distro-upgrades were fine albeit they were point releases though. I have since switched everything to Fedora 42. It's not the end of the world but was annoying enough to switch back.

Seems like such a weird/niche issue. Maybe when Fedora 43 is officially available via the templates within Proxmox this will not be an issue. That's curious that you noticed it being fine in Proxmox 8 and 9.1.4 provided you didn't upgrade past 42. Maybe something was fundamentally changed in 43 that is enough to cause the weird output.

It's something I have to try and look into on the back burner but for now, I redid everything on Fedora 42 and that is good enough for me.

 

[Kingneutron]

This is just a hunch, but looks like Fedora 43 LXC TTY is not translating ANSI Escape codes properly.

Do a search on " linux ansi escape codes 24;80R "

Proper workaround by changing it to /dev/console in the web gui should suffice (and also enables you to see boot messages); I've never really had to use multiple VTs in LXC anyway like you might on a real bare-metal box.

And there are other weird things going on with LXC native console like not adhering to $LINES and $COLUMNS in bare terminal (without GNU screen / tmux) when doing apt upgrade. That gets you some ASCII screen corruption, with the thing thinking it's limited to like 80x25 when it's not.

The other workaround is just to ssh into the LXC, or use ' pct enter vmid ' over ssh or from the PVE Console.

 

[guruevi]

As @Kingneutron said - the reason is that Fedora is outputting ASCII/shell escape sequences that is not compatible with your terminal type. That is not a fault with LXC/Proxmox, but can also appear over SSH, Telnet or Serial Port. This could be caused by those characters in /etc/motd, /etc/issue etc.

One thing to also check or set is the locale settings for your OS and terminal (export TERM=C). You can also change the underlying terminal that gets launched when you open a shell, I forgot how exactly, but it’s typically getty or something similar.