Re: What are folks using for serial consoles these days?

[Ryan Hamel via NANOG <nanog () lists nanog org>]

VyOS has a built-in conserver (https://docs.vyos.io/en/latest/configuration/service/console-server.html). All one needs 
is a box to put it on, and it allows for customization with serial ports, power, connectivity, and of course having a 
firewall for an out-of-band network. Considering the number of ways to deploy VPNs and setup conserver, this setup can 
allow for centralized "conserver" endpoints for quickly getting into devices.

Job had a presentation (https://nlnog.net/static/nlnog_live_summer_2020/NLNOG_Live_Job_Snijders_NTT_IP_OOB.pdf) similar 
to what I described, but with a Cisco ISR router, replacing those older 2500 series devices.

Adair Thaxton did a presentation on Internet2's out-of-band setup (https://youtu.be/ZuAZCA5lzww).

Dan Baxter did a presentation on cellular out-of-band (https://youtu.be/hBX81XrXw18), which could be useful here.

Ryan Hamel

________________________________
From: Brandon Martin via NANOG <nanog () lists nanog org>
Sent: Sunday, December 21, 2025 1:12 PM
To: nanog () lists nanog org <nanog () lists nanog org>
Cc: Brandon Martin <lists.nanog () monmotha net>
Subject: Re: What are folks using for serial consoles these days?

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On 12/19/25 12:54, Chris Adams via NANOG wrote:
> Cisco 2500 series used a 68EC030, which is a dumbed-down 68030 with no
> MMU.  The Linux m68k project always required an MMU, so it would not run
> on that CPU.

FWIW, MMU-less Linux is a thing and is no longer a separate fork.  It's
supported by the mainline kernel sources.  Just turn off CONFIG_MMU.
M68k should be supported for this purpose along with most other popular
architectures were MMUs are not an inherent part of the CPU architecture
including ARM and PPC.

You also still need enough RAM.  The bare minimum is 4MB, and 8MB is far
more realistic, and that's just for the kernel itself.

The result, though, is a system with some serious limitations which was
also true of the old uClinux fork.  In particular, there's no way to run
most standard ELF executables.  You either need to use uclinux FLAT ABI
images (which does not support dynamic linking at all) or the much newer
(and with tenable toolchain support) FDPIC ELF ABI.

Either ABI imposes limitations on what userspace can do.  For example,
fork(2) doesn't work, though vfork does.  OpenSSH doesn't even compile
against the relevant headers IIRC, but dropbear does though I had
trouble getting it to work at last attempt.

Support for various other features often considered sundry to Linux
varies, too.  For example, on ARMv7-M, causing a segmentation fault from
userspace will crash the entire system with rather terse kernel panic
instead of terminating the offending process.  This is not a technical
limitation but rather a lacking implementation.  Debuggers also don't
work properly and instead lock the system up (ditto regarding it not
being a technical limitation AFAIK).

I'm not sure that really solves the desire to meaningfully run Linux of
this platform for the purpose intended.
--
Brandon Martin
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