[SOLVED] LiveUSB stuck after Grub on new system

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

I cannot get past Grub using the liveUSB minimal installation CD (20250322).
I believe it's an early kernel panic, exactly as described here: https://forums.gentoo.org/viewtopic-t-1167043-start-0.html

I get to grub no problem, press enter to start the first entry but then it gets stuck with this message:

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

It looks like it is something related to the graphics drivers, probably amdgpu non being used.

I attached an old screen to the VGA port of the mobo, that is connected to the BMC, and I can see it boot fine using the gentoo live USB.

pietinger · Posted: Thu Mar 27, 2025 2:56 pm Post subject:

snake111,

did you use the latest UbuntuLiveCD? Your cross-check with Ubuntu was very useful because usually the Ubuntu kernel is heavily patched (and also the firmware is always very new). If your system does not (yet) boot with Ubuntu, the only thing you can do at the moment: Wait.

The drivers for an amdgpu are patched in almost every new minor version of the kernel. This means that sometimes it helps to use the next minor version.
_________________
https://wiki.gentoo.org/wiki/User:Pietinger

NeddySeagoon · Posted: Thu Mar 27, 2025 3:32 pm Post subject:

snake111,

That's a server motherboard. It will have several different consoles.

The one you see if you connect a VGA display, that's connected to the AST 2600.
The serial over LAN (SoL) that you get with ipmitool. There may be several SoL consoles too.
The one you see if you connect to the Board Management Computer (BMC) web interface.
Another one if you have a some other GPU.

IPMItool with SoL is as good as it gets. This IPMItool]section may give you some pointers. Its for a completely different board but it uses the AST 2600 too.

Play with SoL, see what you can see.
If there is a panic, you can capture all the gory detail. That's the nice thing about serial.

You may need to add the console on serial port instruction to the kernel command line.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

NeddySeagoon · Posted: Sat Mar 29, 2025 11:01 am Post subject:

snake111,

The VGA port on the motherboard comes from the AST 2600 BMC, not the amdgpu embedded in your CPU.
It uses the ast2x00 (from memory) kernel DRM driver. AMDGPU is not involved.

I suspect that the LiveUSB is drawing the console on one GPU and you are looking at another.
dmesg would confirm that. SoL with ipmitool would show all. You will need a console command on the kernel command line to put a copy of the console on ttfS0, and configule the firmware to redirect ttyS0 to SoL.
You even get the firmware setup there too.

If you can get into the BIOS, its usually possible to set the primary GPU.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

I know that the VGA is not from the CPU/GPU, it's pretty clear from the manual, see my second message.
I also tried with a Ryzen with no integrated GPU and the VGA out was working while HDMI obviously not, since there was no GPU to drive it.

I agree that the LiveUSB is pushing the console/output on the VGA. If I attach two monitors that's exactly what happens: I get the post and GRUB on both monitors, but then HDMI remains stuck as described in my first message, while on VGA I can see the kernel loading and the login prompt after that.

I might need to investigate using ipmtool, but I have no experience in that. I tend to agree with you that it looks like I'm missing some kernel command to redirect/instruct to use the HDMI as output, I'll try to see if I find something.
I tested a few bios settings for the main GPU, but made no difference. In fact the BIOS already uses the HDMI output, all the way till grub. So not sure if any setting there is able to affect what's being used by the kernel?

NeddySeagoon · Posted: Sat Mar 29, 2025 4:06 pm Post subject:

snake111,

Can you put dmesg onto a pastebin please?

You can use the video option on the kernel command line to set the things you want but one of the things you can tell it is the framebuffer driver you want to use.
Its good to know that you have all the bits for amdgpudrmfb before you try to use it or you will get a blank console.

Your kernel is not panicing, its using the built in AST 2600 video card.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

I found a way

So first I looked ad the video= boot option as you suggested. On this Freedesktop KMS page it says that you can specify a video port option, like DVI-I-1, VGA-1 and so on.
Problem is that I couldn't find a reference for the port names, so I tried HDMI, HDMI-1, but no luck.

Then I had a closer look at my dmesg and I could see that the two framebuffer devices had already been detected correctly: fb0 using the VGA port of the BMS, and fb1 using the amdgpu driver, below the kernel line from dmesg.

pietinger · Posted: Mon Mar 31, 2025 4:21 pm Post subject:

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

Thanks! Love that, 20 years after my first install Gentoo is still a gem of the internet and linux scene <3

snake111 · Tux's lil' helper Joined: 18 Dec 2004 Posts: 124

Related issue for someone in a similar situation: the GRUB menu is not showing with the standard Gentoo handbook instructions.
I fixed it with this GRUB option: