headless server with console on USB port

[Rainer Dorsch]

Hi,

is it possible to run a console on a USB port of a headless server?

The system is a Dell T20 machine

https://www.hardwareluxx.de/community/threads/dell-poweredge-t20.1031138/

(the page is in German, but I am not aware of an English version with a
similar level of detail)

rd@master:~$ inxi -M
Machine: Type: Desktop System: Dell product: PowerEdge T20 v: 00 serial:
<superuser required>
Mobo: Dell model: 0VD5HY v: A07 serial: <superuser required> BIOS:
Dell v: A14 date: 11/27/2017
rd@master:~$

with several Intel USB host controller

rd@master:~$ lspci|grep -i usb
00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family
USB xHCI (rev 04)
00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family
USB EHCI #2 (rev 04)
00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family
USB EHCI #1 (rev 04)
rd@master:~$

How would I know to which of the multiple USB ports to connect to?

Many thanks
Rainer

--
Rainer Dorsch
http://bokomoko.de/

[Dan Ritter]

Rainer Dorsch wrote:
> is it possible to run a console on a USB port of a headless server?

Yes and no.

The T20 doesn't seem to have iDRAC (IPMI) support, so BIOS/UEFI
is not available through a serial console.

The first time you have an opportunity for a serial console is in GRUB;
then again you have an opportunity for the kernel output; then finally
you can have a login on a serial terminal.

You will need a USB to RS232 serial adapter, and then an appropriate
cable to talk to your terminal device. The other end can also be a USB
to RS232 serial adapter. In between you might have a 9 pin
serial cable or a specially wired RJ45 (looks like ethernet)
cable.

The name of the device should be something like /dev/ttyS0
(S1,S2,S3...) or can be /dev/ttyUSB0. USB ports can be renumbered on
each boot, but as long as there is only one serial adapter connected,
it should always be recognized as /dev/ttyUSB0

-dsr-

[Rainer Dorsch]

Hi Dan,

thanks for the quick response and explanations. That helps a lot to understand
how it is supposed to work. I do not care about the BIOS output, I rarely
touch bios settings, my usecase are OS upgrades, grub would be nice, but
kernel output and a terminal is what I was hoping for.

I am wondering if ready-made usb-to-usb solutions exist, which contain the
conversion to serial and back to usb internally....or if there are a serial
crossover cable and two usb-to-serial adapters in some boxes in our cellar :-)

Thanks again
Rainer

[Reco]

Hi.

On Thu, Aug 18, 2022 at 04:48:34PM +0200, Rainer Dorsch wrote:
> I am wondering if ready-made usb-to-usb solutions exist, which contain the
> conversion to serial and back to usb internally....

I cannot call it "ready-made", but there's something similar - [1] which
may solve your problems.
It does not deal with serial per se, but achieves much more.
Some assembly is required though.

> or if there are a serial
> crossover cable and two usb-to-serial adapters in some boxes in our cellar :-)

That will work, I have similar setup back in the day.
The main problems of such setup are:

- overcomplicated setup of GRUB's USB stack.

I.e. forget about seeing GRUB's menu.

- unless you're using self-built Linux kernel - forget about seeing
those boot messages.

Because to convince the kernel to use that "console=ttyUSB0" argument
you'll need to load an appropriate kernel module first.
Such setup is good for saving you from the descent to the cellar in the
case of occasional network misconfiguration, but that's about only
problem it's good for.



Hardware platforms with built-in UART are easier in this regard, but -
it's very rare to have UART on a consumer-grade x86 motherboard.

[1] https://github.com/Fmstrat/diy-ipmi

Reco

[Tixy]

On Thu, 2022-08-18 at 16:48 +0200, Rainer Dorsch wrote:
[...]

> I am wondering if ready-made usb-to-usb solutions exist, which contain the
> conversion to serial and back to usb internally

I just googled 'usb null modem cable' and got this:
https://ftdichip.com/products/usb-nmc-2-5m/
which is available from lots of electronics suppliers, e.g.
https://www.digikey.de/de/products/detail/ftdi-future-technology-devices-international-ltd/USB-NMC-2-5M/2441364

--
Tixy

[Rainer Dorsch]

Thanks Reco for sharing your thoughts.

Am Donnerstag, 18. August 2022, 17:11:52 CEST schrieb Reco:
> Hi.
>
> On Thu, Aug 18, 2022 at 04:48:34PM +0200, Rainer Dorsch wrote:
> > I am wondering if ready-made usb-to-usb solutions exist, which contain the
> > conversion to serial and back to usb internally....
>
> I cannot call it "ready-made", but there's something similar - [1] which
> may solve your problems.
> It does not deal with serial per se, but achieves much more.
> Some assembly is required though.
>
> > or if there are a serial
> > crossover cable and two usb-to-serial adapters in some boxes in our cellar
> > :-)
> That will work, I have similar setup back in the day.
> The main problems of such setup are:
>
> - overcomplicated setup of GRUB's USB stack.
>
> I.e. forget about seeing GRUB's menu.
>
> - unless you're using self-built Linux kernel - forget about seeing
> those boot messages.
>
> Because to convince the kernel to use that "console=ttyUSB0" argument
> you'll need to load an appropriate kernel module first.
> Such setup is good for saving you from the descent to the cellar in the
> case of occasional network misconfiguration, but that's about only
> problem it's good for.

I hope that it also helps to give some hint on what is going wrong and if it
is need to walk in the cellar or if a timeout is counting down and I can just
wait long enough.

Also if I need to boot a recovery system from a USB stick, I do not have to
walk down and connect a monitor.

>
> Hardware platforms with built-in UART are easier in this regard, but -
> it's very rare to have UART on a consumer-grade x86 motherboard.
>
> [1] https://github.com/Fmstrat/diy-ipmi

Ah, I see, getting USB up early might be a problem.

Would a native serial interface on a PCI card be a better solution?

Thanks
Rainer

[Rainer Dorsch]

Hi Tixy,

thanks for sharing the useful search term. I found another one

https://hackaday.com/2020/08/25/the-usb-null-modem-cable-is-now-a-thing/

Unfortunately, it seems that tindie (see link in one of the last comments)
does not ship the USB-USB NULL Modem (CDC) to Germany :-/

Thanks again
Rainer

[Reco]

On Thu, Aug 18, 2022 at 06:28:56PM +0200, Rainer Dorsch wrote:
> Ah, I see, getting USB up early might be a problem.
>
> Would a native serial interface on a PCI card be a better solution?

Same problem, different interface.
You need UART that's soldered on the motherboard. Sadly, there's no
substitutes to this.

And if you really considering PCI-X card, I suggest buying something
like [1].


[1] https://www.amazon.com/Dell-G8593-DRAC5-PCI-Controller/dp/B00450FDR6

Reco

[Stefan Monnier]

> Hardware platforms with built-in UART are easier in this regard, but -
> it's very rare to have UART on a consumer-grade x86 motherboard.
> [1] https://github.com/Fmstrat/diy-ipmi

I suspect you can simplify it with one of those SBCs that come with an
HDMI-in port. But it still seems Rube Goldbergish.


Stefan

[Tim Woodall]

Maybe not what you want but I've used a rpi4 with hdmi to usb capture to
control a pc from the bios. The pi4 can emulate the keyboard as well as
doing the hdmi capture.

I've even got some kicad schematics to control the power and reset and
monitor the power and usb leds. But I'm not a hardware developer so,
while it 'works for me' people who actually know what they're doing
might be horrified... but I can post them if they will be of interest.

[David Christensen]

What about using the "Serial connector" on the back of the machine as a
serial console? See Dell PowerEdge T20 Owner's Manual, Figure 2, Item 9:

dl.dell.com/topicspdf/poweredge-t20_owners-manual_en-us.pdf


David

[Rainer Dorsch]

Ooohh...where is the brown paper bag?

Many thanks David, I will try that one.

Thanks