2

I have a HP ThinClient computer (t5740) for a special use. Since it has VGA output, I can only connect it via VGA-to-HDMI converter to a monitor (it does not have VGA input).

When it boots the BIOS screens in the low resolution and big default fonts display works all right. grub screen occasionally also gets displayed.

However, once kernel starts booting and switches video output to some different mode and to smaller fonts, the image disappears and monitor switches into a sleep mode after a few seconds.

Since the BIOS screens display fine, I want to switch kernel's/grub's video mode (resolution, refresh rate, font size etc) to exactly this kind of configuration. I have tried all kinds of ways like dpkg-reconfigure console-setup, setting various video modes in grub.cfg and whatever I could find on the web. Nothing worked.

How can I make grub/kernel use exactly the most basic video mode that the box displays during BIOS operations?

OS: Debian Buster (10), i386 arch (that's the CPU).

1

1 Answer 1

1

I managed to solve it. In /etc/default/grub set following variables:

GRUB_CMDLINE_LINUX_DEFAULT="quiet nomodeset"
GRUB_CMDLINE_LINUX=""

GRUB_GFXMODE=1024x768@60
GRUB_GFXPAYLOAD_LINUX=keep

Run update-grub afterwards.

nomodeset alone did not solve the problem. I had to specifically set GRUB_GFXMODE and GRUB_GFXPAYLOAD_LINUX like this.

It is instructive to use fbset to check actual video mode set. For some reason after boot it was always 1920x1440 no matter what I set previously with GRUB_GFXMODE alone. Apparently that mode is outside resolutions supported by my VGA2HDMI converter.

It may have had something to do with Intel graphics. This computer has Intel graphics chipset (Mobile 4 Series Chipset Integrated Graphics Controller) and I've seen people around the web doing some Intel-related kernel module blacklisting to get video working properly.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .