On 2020-12-27 at 17:23, tomas@tuxteam.de wrote: > On Sun, Dec 27, 2020 at 05:08:27PM -0500, The Wanderer wrote: > > [...] > >> I have the impression that things have by now developed to the >> point where a physical serial-port cable (of the classic type of >> serial port and cable, whose connectors can be visually confused >> with a VGA port in some cases) is no longer necessary, which is >> good, since if we ever had such a thing it was at least back in the >> days of PS/2 keyboards and mice and might have been back in the >> days before our home computers had internal hard drives. > > "Modern" computers tend to lack serial ports (sometimes a pity, but > well...) > > Still I doubt it would be any help. You made a credible case that > there is a hard lockdown at the handover from the BIOS to GRUB. You'd > have to be very lucky for GRUB to utter a last sigh over serial > before that. > > My impression is that the video card reacts allergically to some > modeset attempt by GRUB and this causes a pretty low level lockup. I've had similar thoughts, but if that were the case, I'd expect that telling GRUB to use "console" output would avoid the problem, by having it not do any modesetting. My most recent attempt was with terminal_input and terminal_output set to "console", and the problem persisted. I do see various modules listed in the grub.cfg load_video function, and it's not impossible that the process of trying to use one or more of those includes some action which triggers this behavior. I haven't found a place to configure that, though - or I hadn't until now; it's in /etc/grub.d/00_header, and can be overridden to a single module by defining GRUB_VIDEO_BACKEND (presumably, in /etc/default/grub). I might pursue that if the live-boot environment doesn't give fruitful results. -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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