[SOLVED] How do I set the framebuffer to 80x25?

swapjim · 10-22-2023, 04:31 PM

This is my lilo.conf:

Code:

append = " "

boot = /dev/sda
compact

prompt
timeout = 10
change-rules
reset
vga = normal

image = /boot/vmlinuz
  root = /dev/sda1
  label = Slackware15
  read-only

In case it matters I'm running Slackware inside VirtualBox.

I thought that by setting vga = normal I would get a 80x25 terminal but instead I get something that's has a lot more lines and columns.

I know that I can set a larger font but I'd like to know first if there is way to change the resolution.

allend · 10-22-2023, 08:21 PM

I suggest commenting out "vga = normal" and adding "vga = ask", then booting and experimenting with the modes available on your system. Once you find a mode you like, then you can set it as the default.
Some examples:

Code:

# Normal VGA console
vga = normal
# Ask for video mode at boot (time out to normal in 30s)
# vga = ask
# VESA framebuffer console @ 1280x1024x64k
#vga=795
# VESA framebuffer console @ 1024x768x64k
#vga=791
# VESA framebuffer console @ 1024x768x32k
#vga=790
# VESA framebuffer console @ 1024x768x256
#vga=773
# VESA framebuffer console @ 800x600x64k
#vga=788
# VESA framebuffer console @ 800x600x32k
#vga=787
# VESA framebuffer console @ 800x600x256
#vga=771
# VESA framebuffer console @ 640x480x64k
#vga=785
# VESA framebuffer console @ 640x480x32k
#vga=784
# VESA framebuffer console @ 640x480x256
#vga=769

You can also add a kernel parameter to specify the screen resolution once the kernel takes control with something like:

Code:

append = " video=VGA-1:1920x1080@60"

For further details see /usr/src/linux//Documentation/fb/modedb.rst
To discover the names of outputs being used by the kernel look at the output of 'ls /sys/class/drm'.

BTW - I suggest also including " vt.default_utf8=1" in the append line.

Code:

append = " vt.default_utf8=1 video=VGA-1:1920x1080@60"

Note that the space character at the start of the quoted string is necessary.

Also I suggest adding the large-memory option in your lilo.conf

Code:

compact
large-memory

swapjim · 10-24-2023, 04:03 PM

Thanks for your reply!

I played a bit with the modes using vga = ask and what I found is that I can indeed change the resolution (and I can see the pengiun logo at the top left of the screen), but as the kernel keeps scrolling lines, a few seconds later, resolution changes to something that seems to remain fixed no matter what resolution I pick. Also, tux stops appearing. Does that give any hint to what's happening?

Adding append = " video=VGA-1:1920x1080@60" didn't made a difference with this. I haven't looked at the /usr/src/linux//Documentation/fb/modedb.rst and /sys/class/drm yet, but I will in the following days.

I added large-memory and vt.default_utf8=1. Thanks for the tips!

If you have any more things I can try then please do.

allend · 10-24-2023, 06:26 PM

Quote:

but as the kernel keeps scrolling lines, a few seconds later, resolution changes to something that seems to remain fixed no matter what resolution I pick. Also, tux stops appearing. Does that give any hint to what's happening?

This is when the kernel DRM takes over.

You will need the correct graphics output name for the video= option.
Perhaps you could post the output of ‘ls /sys/class/drm’?

swapjim · 10-25-2023, 01:42 PM

Code:

$ ls  -l /sys/class/drm
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-1 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-1/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-2 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-2/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-3 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-3/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-4 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-4/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-5 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-5/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-6 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-6/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-7 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-7/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 card0-Virtual-8 -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-Virtual-8/
lrwxrwxrwx 1 root root    0 Oct 25 18:31 renderD128 -> ../../devices/pci0000:00/0000:00:02.0/drm/renderD128/
-r--r--r-- 1 root root 4096 Oct 25 18:31 version

$ cat /sys/class/drm/card0/card0-Virtual-1/modes
800x600
1920x1440
1856x1392
1792x1344
1920x1200
1920x1080
1600x1200
1680x1050
1400x1050
1280x1024
1440x900
1280x960
1360x768
1280x800
1152x864
1280x768
1280x720
1024x768
800x600
640x480

Aeterna · 10-26-2023, 12:29 AM

use

Quote:

fbset

to get actual video mode. If you want to go beyond vga=795, probably you would need to append
GRUB_GFXMODE:

Quote:

GRUB_GFXMODE=1920x1440x24
GRUB_GFXPAYLOAD_LINUX=keep

if would not work, your setup may be limited to

Quote:

vga=795

allend · 10-26-2023, 08:17 AM

Thanks for the listing.
It shows multiple graphic output names, Virtual-1 to Virtual-8.
I suggest trying an append line with VGA-1 replaced with Virtual-1.

PS - The OP appears to be using LILO. GRUB parameters are not relevant.

Aeterna · 10-26-2023, 08:44 AM

Quote:

Originally Posted by allend

Thanks for the listing.
It shows multiple graphic output names, Virtual-1 to Virtual-8.
I suggest trying an append line with VGA-1 replaced with Virtual-1.

PS - The OP appears to be using LILO. GRUB parameters are not relevant.

I am sorry for my mistake. Unfortunately, this may be argument for grub and against lilo/elilo. Unless your suggestion will work of course.

allend · 10-26-2023, 09:03 AM

The OP is booting Slackware in VirtualBox.
There is no need to emulate a UEFI system. LILO is sufficient, saving disk space and complexity.

rkelsen · 10-27-2023, 11:50 PM

I tested this today. It only works if you disable EFI booting, and use LILO to boot from the MBR.

All you need to do is append "nomodeset" to your kernel command line. In your /etc/lilo.conf file, you'd do it like so:

Code:

append = " "

boot = /dev/sda
compact

prompt
timeout = 10
change-rules
reset
vga = normal

image = /boot/vmlinuz
  root = /dev/sda1
  label = Slackware15
  append = "nomodeset"
  read-only

Leave the quote marks there, exactly like that. Run lilo after editing the file and reboot. It should start in 80x25 text mode.

swapjim · 10-29-2023, 05:12 PM

Quote:

Originally Posted by rkelsen

Code:

append = " "

boot = /dev/sda
compact

prompt
timeout = 10
change-rules
reset
vga = normal

image = /boot/vmlinuz
  root = /dev/sda1
  label = Slackware15
  append = "nomodeset"
  read-only

Hey, that did the trick! Thanks a lot!

I have a follow up question. Apparently I have configured things with MBR, which I didn't remember. Is this configured during installation? Or in the BIOS settings of VirtualBox? Where can I learn more about this?

rkelsen · 10-29-2023, 05:44 PM

Quote:

Originally Posted by swapjim

Apparently I have configured things with MBR, which I didn't remember. Is this configured during installation? Or in the BIOS settings of VirtualBox? Where can I learn more about this?

It's the default setting in VirtualBox, and I think (but I may be wrong) that it's because work on virtualising EFI booting is not quite complete. At this stage you can use it and it should work. A VM is the ideal place to learn how EFI booting works.

Beware that 80x25 text mode will not work if you switch to EFI booting. This is because UEFI doesn't support text or VGA modes.

swapjim · 10-31-2023, 05:47 PM

Thank you and thanks everyone who posted!