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Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

[Solved] Screen output at boot time

Hello:

Info: my rig runs on the latest Devuan ASCII ...

groucho@devuan:~$ uname -a
Linux devuan 4.9.0-6-amd64 #1 SMP Debian 4.9.88-1+deb9u1 (2018-05-07) x86_64 GNU/Linux
groucho@devuan:~$ 

... and It is up to date.

root@devuan:/home/groucho# apt-get dist-upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@devuan:/home/groucho# 

From back in my MS days, I have always had the habit of looking at the screen output at boot time.
Sure, it can scroll by fast enough but I can get a remote idea of what's going on and go have a look at the logs if I notice something off while it passes by.

Much better yet if it is colour coded and has timestamps, like when I run dmesg from a terminal as root.

The thing is that the boot time output on my screen is not in it's native 1280*1024 but what seems to be 640*480 and I have not been able to get it to show in 1280*1024.

I have tried adding vga=791 or 792 to the grub stanza to no avail.
I have also tried GRUB_GFXPAYLOAD_LINUX 'keep'.

Can I get it Devuan to boot as I want to?
Is it also at all possible to get the output at boot time in the same way I get dmesg from a terminal?

Thanks in advance,

A.

Last edited by Altoid (2018-06-23 14:34:34)

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

The thing is that the boot time output on my screen is not in it's native 1280*1024 but what seems to be 640*480 and I have not been able to get it to show in 1280*1024.

I have tried adding vga=791 or 792 to the grub stanza to no avail.
I have also tried GRUB_GFXPAYLOAD_LINUX 'keep'.

You could try changing the grub gfxmode in /etc/default/grub (line 23):

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480 <---

and run update-grub.

devuser

Member

Registered: 2018-04-30

Posts: 176  

Re: [Solved] Screen output at boot time

Yeah, i'd try what emanym said. Get grub to use a higher resolution can be a bit annoying but i've done it in the past (sorry forgot the exact combination of settings) so it should be possible.

As for boot messages i'd try editing /etc/default/grub to remove quiet from GRUB_CMDLINE_LINUX_DEFAULT and also run update-grub.

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

No ..
Won't do.

Spoke too soon.  =^/

This is how it is done:
https://wiki.debian.org/GrubTransition

Grub 2 and the VGA parameter
In Grub2 the vga= parameter is deprecated.
To set a screen resolution for your console you can do the following log in as root:

edit /etc/default/grub
uncomment the GRUB_GFXMODE=640x480 and change the resolution to something you can use e.g. 1024x768

Add the line
GRUB_GFXPAYLOAD_LINUX=keep
to the file to have the same resolution at the Linux console. You do not edit the 00_header file as some suggest you need to do.
run update-grub

It happens that it does work ...
But if I boot directly from the drive hosting Devuan that is.

In my setup, my first drive hosts a PCLinuxOS installation, another systemd free OS I have been using since before Devuan.

My second drive hosts my Devuan ASCII installation which also has a grub2 setup just in case my PCLinuxOS drive goes south.
My third drive is an old W7 installation I keep in a SATA drive for reference purposes, it's getting scrubbed soon.

In any case, when I boot my rig it starts from the first drive and its grub2 installation offers me to boot into PCLinuxOS, Devuan ASCII or W7 from there.
If I remove this first drive, the rig boots from the second drive and its grub2 installation offers me me to boot into PCLinuxOS Devuan ASCII or W7 from there (obviously it does not find PCLOS).

If the second drive gets set up as a first drive, the same thing happens, with the order changed.

The thing is that when I boot my rig without the first drive in place, Devuan ASCII boots as I want to, with the screen size I set.
But if I boot into Devuan ASCII selecting it from the grub2 menu, it does not.

I had the idea that grub2 looks for other OSs and boots them according to what the grub.conf file in the drive hosting that OS says.
ie: the screen size set by GRUB_GFXMODE.

But it seems this is not the case.

Or am I doing something wrong?

Thanks in advance.

A.

Last edited by Altoid (2018-06-20 22:55:24)

devuser

Member

Registered: 2018-04-30

Posts: 176  

Re: [Solved] Screen output at boot time

Makes me wonder if there's some kernel compilation magic that could be missing.

Don't think so as the grub screen is shown before the kernel is even loaded. Iirc it's just a matter of getting the right combination of settings in /etc/default/grub. Sadly all i remember is that it was annoying to figure out but grub being bugged nowadays is of course also an (imo unlikely) possibility.

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

No ..
Won't do.

The graphics mode or the verbose boot?
For verbose boot use devuser's answer....

For grub graphics mode:
try interrupting grub before boot, and open a grub commandline by typing c (escapeto quit)

The videoinfo command should give information about available video modes, and the one currently selected (marked with a *).

It is possible to set the gfxmode directly in /boot/grub/grub.cfg, but not a good idea -- it would get overwritten on grub or kernel updates.

What happens if you boot devuan from the pclinux grub?

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

Sadly all i remember is that it was annoying to figure out but grub being bugged nowadays is of course also an (imo unlikely) possibility.

Rumour has it grub was designed by the same committee that designed the camel and the dodo ;-)

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

Sorry ...
My intention was to quote myself and instead I ended up editing my previous post.

Please reply to this one: https://dev1galaxy.org/viewtopic.php?pid=10267#p10267

Thanks in advance.

A.

Last edited by Altoid (2018-06-20 23:05:12)

devuser

Member

Registered: 2018-04-30

Posts: 176  

Re: [Solved] Screen output at boot time

I had the idea that grub2 looks for other OSs and boots them according to what the grub.conf file in the drive hosting that OS says.
ie: the screen size set by GRUB_GFXMODE.

Not entirely sure here but i don't think so. Imo grub only reads one associated config which controls to which mode it switches and if it keeps the resolution when loading the kernel. So if Devuan gets loaded in a higher resolution is controled by the config of the grub installation in PCLinuxOS. No guarantees, i might be completly wrong here.

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

Grub, or os-prober actually, looks at any partition it can find for other operating systems, and 'guesses' how to boot that os.

The grub versions from devuan, debian(-derivatives), pclinuxos and manjaro are pretty good at guessing, some others make a mess of it.

The resolution of the grub menu at boot is determined by the grub configuration from the 'local' linux version, not the grub configuration of 'other' versions.

I'm not sure why it should influence the console resolution after linux was booted...

devuser

Member

Registered: 2018-04-30

Posts: 176  

Re: [Solved] Screen output at boot time

I'm not sure why it should influence the console resolution after linux was booted...

Yeah, once the system is booted it's up to the OS to use it's own settings. My guess is the kernel by default simply doesn't bother changing the resolution and just uses whatever grub has left behind. Way later console-setup kicks in and maybe changes stuff a bit. Just had a quick look and /etc/default/console-setup seems to have a VIDEOMODE option too. Not really sure what it does as i just use it to set an oldschool ascii friendly font. Besides all of that would happen way after the kernel boot messages are done anyways.

cynwulf

Member

Registered: 2017-10-09

Posts: 234  

Re: [Solved] Screen output at boot time

The fact that you don't have a native resolution console, usually means that you don't have the console framebuffer loaded.

On most hardware made in around the last 15 or so years, once Linux KMS kicks in, your screen resolution will change to the LCD panel's native resolution.  If it isn't it may be due to some very old or obscure hardware or some changes you have made locally.

The other possibility is the proprietary AMD or Nvidia video drivers are installed?  As I recall these blacklist the Linux KMS/DRM stuff and load their own modules in their place.  But it's years since I've used any of those, so that could have changed.

I can't help much with grub as I don't use it, but it is only passing the console resolution you set to the kernel (bootloaders support passing all kinds of options to the kernel).  The best you will get out of it is probably going to be something like 1024x768 (but it has to be a supported VESA mode and not what you think your graphics adaptor or monitor can handle).

Last edited by cynwulf (2018-06-21 09:37:41)

Panopticon

Member

Registered: 2018-01-27

Posts: 306  

Re: [Solved] Screen output at boot time

Where do you $ sudo update-grub from? Pc linux os or Devuan?

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

Sorry for the delay in answering.
Automatic subscription was off ... =^/

The other possibility is the proprietary AMD or Nvidia video drivers are installed?

Yes. I am using the Nvidia non-free drivers.

It was the only way to get my two cards and three monitors to play nice.
RandR gets disabled because of Xinerama but I don't think it has anything to do with this.

Where do you $ sudo update-grub from? Pc linux os or Devuan?

I was looking into a possible version mismatch this morning.

PCLinuxOS uses Grub2 2.02.0-3
Devuan uses 2.02Beta3-5

I don't know if there's any real difference between these two, but ...

If both installations run of the same hardware and the problem in the Devuan installation arises when I boot it from the grub2 in PCLinuxOS and not with it's own grub2, then the problem seems to be with how grub2/PCLinuxOS "talks" with grub2/Devuan.

Is it a version mismatch or is it a configuration issue?
ie: is there something that grub2/PCLinuxOS needs to know or find to boot Devuan the same way it boots from its own grub2?

Thanks for your input.   =-)

Cheers,

A.

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

PCLinuxOS uses Grub2 2.02.0-3
Devuan uses 2.02Beta3-5

I don't know if there's any real difference between these two, but ...

Grub from pclinuxos  and grub from devuan may use slightly different boot command lines to boot devuan, you could check by doing:

cat /proc/cmdline

on both "devuan booted from devuan grub", and "devuan booted from pclinuxos grub", or by comparing the command lines used in both grub configs directly, something like

grep -A 13 evu /boot/grub/grub.cfg | grep vmli

in devuan and pclinuxos should work, although you would get multiple hits. Only the first one matters...

cynwulf

Member

Registered: 2017-10-09

Posts: 234  

Re: [Solved] Screen output at boot time

Yes. I am using the Nvidia non-free drivers.

That's most likely why you have a text mode console (e.g. 80x50 characters).

I can't really advise on your grub setup, but if you're booting directly rather than chainloading, this could be the problem.  The best approach is to either just install one bootloader on one OS and use that to directly boot the other, or set up that bootloader to chainload to the other's bootloader.  It's actually pointless to try and replicate the same setup on both.

Panopticon

Member

Registered: 2018-01-27

Posts: 306  

Re: [Solved] Screen output at boot time

Maybe try updating grub from Devuan with the PC linux os drive in place and mounted inside Devuan? You will still have the Devuan menu entry as number one but you can default grub to select PC linux os.

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

Grub from pclinuxos and grub from devuan may use slightly different boot command lines to boot devuan ...

Let's see.
Here's what I got:

From PCLinuxOS

[groucho@groucho ~]$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.12.10-pclos1 root=UUID=82ca71e8-fba7-4e36-a086-27e3be13a48b ro nokmsboot noiswmd resume=UUID=464724a6-5814-4f99-b422-3e180aabed08
[groucho@groucho ~]$

[groucho@groucho ~]$ grep -A 15 evu /boot/grub2/grub.cfg | grep vmli
menuentry "Devuan GNU/Linux (on /dev/sda1)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.9.0-6-amd64--d6841f29-e39b-4c87-9c52-3a9c3bafe2d3' {
		linux /boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro
menuentry "Devuan GNU/Linux, with Linux 4.9.0-6-amd64 (on /dev/sda1)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.9.0-6-amd64--d6841f29-e39b-4c87-9c52-3a9c3bafe2d3' {
		linux /boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro nokmsboot
menuentry "Devuan GNU/Linux, with Linux 4.9.0-6-amd64 (recovery mode) (on /dev/sda1)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.9.0-6-amd64-root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro single-d6841f29-e39b-4c87-9c52-3a9c3bafe2d3' {
		linux /boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro single
[groucho@groucho ~]$ 

From Devuan

groucho@devuan:~$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro
groucho@devuan:~$

groucho@devuan:~$ grep -A 15 evu /boot/grub/grub.cfg | grep vmli
	linux	/boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro 
		linux	/boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro 
		linux	/boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro single 
groucho@devuan:~$

As you can see, booting Devuan is done by both OSs in the same way with the same commands:

PCLinuxOS

linux /boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro

Devuan

linux /boot/vmlinuz-4.9.0-6-amd64 root=UUID=d6841f29-e39b-4c87-9c52-3a9c3bafe2d3 ro

I removed nokmsboot (used prevent KMS driver from loading) from the PCLinuxOS stanza but it made no difference and PCLinuxOS still boots fine.
I cannot recall why it was there so I probably won't be put in again unless something happens.
Maybe Nvidia driver updates have made it redundant?

In any case, my Devuan istallation with non-free Nvidia drivers does not seem to require it.

But ...
There's all this in PCLinuxOS:

menuentry "Devuan GNU/Linux (on /dev/sda1)" --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-4.9.0-6-amd64--d6841f29-e39b-4c87-9c52-3a9c3bafe2d3' {

I have no idea if it is something that grub2 in PCLinuxOS has but the Devuan version does not or if it is something the PCLinuxOS packager included.

... most likely why you have a text mode console (e.g. 80x50 characters).

But I don't have this problem when I boot PCLinuxOS.

... is to either just install one bootloader on one OS and use that to directly boot the other

That's what I have. (I assume it is what you are referring to)
I boot PCLinuxOS from it's own installation drive and use that same grub2 screen to choose to boot Devuan if I want to.

... try updating grub from Devuan with the PC linux os drive in place and mounted inside Devuan? You will still have the Devuan menu entry as number one but you can default grub to select PC linux os.

Don't get how that would be done.
I could just try to update the Devuan grub2 without using the official repo (have to find a suitable *.deb file) but I fear possible havok.

Thanks to all for your input.

Cheers,

A.

Panopticon

Member

Registered: 2018-01-27

Posts: 306  

Re: [Solved] Screen output at boot time

Grub stands for, GRand Unified Bootloader.

I believe your issues are most likely a result of how your hdd are mounted. What is taking care of that?

cynwulf

Member

Registered: 2017-10-09

Posts: 234  

Re: [Solved] Screen output at boot time

But I don't have this problem when I boot PCLinuxOS.
[...]
That's what I have. (I assume it is what you are referring to)
I boot PCLinuxOS from it's own installation drive and use that same grub2 screen to choose to boot Devuan if I want to.

You have two drives, each has the grub bootloader installed, each can boot independently and boot either OS?  I'd expect you to have set up each to chainload to the other - but that's not a given.

As I've said, there are two ways of doing this - directly booting the kernel (this only needs one grub for the whole lot) or chainloading to the other drive and that OS' own grub and then booting from that.

No one can really guess as to how you have this set up, as thus far you have not posted the grub configuration files from both OS.

To clarify somewhat, you've stated that "PCLinuxOS" does not have the same problem.  So presumably this boots with the correct console resolution - perhaps native resolution and the nvidia blob is installed there too?

nokmsboot is a parameter you might need for both OS with the blob installed.  If you are going to continue with the blob going forward, then just keep that as standard.

Last edited by cynwulf (2018-06-22 15:49:31)

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

You have two drives, each has the grub bootloader installed, each can boot independently and boot either OS?

Yes.

My first drive hosts a PCLinuxOS installation, it is set as the first drive to boot in the SAS adapter card and uses grub2.
My second drive hosts my Devuan ASCII installation, it is set as the second drive to boot in the SAS adapter card and uses grub2.
My third drive is an old W7 installation I keep for reference purposes, it is set as the third drive to boot in the SAS adapter card (getting scrubbed soon).

When I boot my rig it starts from the first drive and its grub2 installation offers me to boot into PCLinuxOS, Devuan ASCII or W7 from there.
If I remove this first drive (or if the drive fails), the rig boots from the second drive and its grub2 installation offers me me to boot into PCLinuxOS Devuan ASCII or W7 from there (obviously it does not find PCLOS).

If the first and second drives change places, the same thing happens, with the first OS order changed.

... have set up each to chainload to the other - but that's not a given.

No. (I don't think so)

Each installation (PCLinuxOS first and a year later Devuan) was done with only one drive in the first bay.
That way I could only screw up only one thing at a time.=^D! 

... two ways of doing this - directly booting the kernel (this only needs one grub for the whole lot) or chainloading to the other drive and that OS' own grub and then booting from that.

I'm sorry but it's not too clear to me which of these I am doing.
It has worked well and I've always had an OS at hand, which was my primary objective.

For emergencies, I also have a TinyCore Linux installation on an old 1Gb pendrive plugged into a USB socket I discovered on the mobo (Sun Ultra24).   
It's actually saved my skin a couple of times.

... have not posted the grub configuration files from both OS.

I'm sorry for that oversight on my behalf.

What files would you need to see?

... stated that "PCLinuxOS" does not have the same problem.

No.
The screen output at boot is in the correct console resolution.

... boots with the correct console resolution - perhaps native resolution and the nvidia blob is installed there too?

Both PCLinuxOS and Devuan use the non-free Nvidia drivers.

nokmsboot is a parameter you might need for both OS with the blob installed.
If you are going to continue with the blob going forward, then just keep that as standard.

I do not remember adding it so it must have been added by the Nvidia drivers installation?

Looking for some info on this, I came across a post from 2012 in the Mageia forum:
https://forums.mageia.org/en/viewtopic. … 971#p14396

KMS stands for "kernel mode switching". It means that the Linux kernel is responsible for the video frame buffer and for switching between video resolutions, instead of the graphics driver. This is a fairly recent addition to Linux, and not all graphics drivers have caught up with the new way of doing things.

I expect that the nokmsboot parameter was set after I installed the Nvidia drivers in PCLinuxOS. I have not seen anything acting up since I removed it.
Since then I have seen the Nvidia drivers get updated more than once, so maybe they have caught up and the nokmsboot is no longer needed.

It was not put in Devuan when I installed the Nvidia drivers.
Let's see if any problems arise.

--- EDIT ---

I may have come across something:

<-- post Yesterday 06:34:28
The fact that you don't have a native resolution console, usually means that you don't have the console framebuffer loaded.

You're quite right.

From my PCLinuxOS terminal

[groucho@groucho ~]$ dmesg | grep vesafb
[    0.341689] vesafb: mode is 1280x1024x32, linelength=5120, pages=0
[    0.341692] vesafb: scrolling: redraw
[    0.341700] vesafb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    0.341724] vesafb: framebuffer at 0xfb000000, mapped to 0xffffac3140800000, using 5120k, total 5120k

The frame-bufefr is only loaded if I boot Devuan from it's own drive ie: not from PCLinuxOS's grub2.
From my Devuan terminal (booted independently)

[root@devuan groucho]# dmesg | grep vesafb
[    0.645586] vesafb: mode is 1280x1024x32, linelength=5120, pages=0
[    0.645590] vesafb: scrolling: redraw
[    0.645594] vesafb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    0.645612] vesafb: framebuffer at 0xfb000000, mapped to 0xffffad6701800000, using 5120k, total 5120k

--- EDIT ---

Thank you very much for taking the time to write this up.
Much appreciated.

Best,

A.

Last edited by Altoid (2018-06-22 20:07:03)

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

<-- post Yesterday 06:34:28
The fact that you don't have a native resolution console, usually means that you don't have the console framebuffer loaded.

I decided to try editing the grub2 entry for Devuan on my PCLinuxOS, adding vga=845 (1280x1024x32) to the command line.
I know vga=XXX has been deprecated but thought it was worth a shot.

And just what do I see?

My Devuan boot screen shows up at a clean and tidy 1280x1024x32.
Checking further, I see that the vesafb is loaded.

[root@devuan groucho]# dmesg | grep vesafb
[    0.636130] vesafb: mode is 1280x1024x32, linelength=5120, pages=0
[    0.636134] vesafb: scrolling: redraw
[    0.636138] vesafb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    0.636157] vesafb: framebuffer at 0xfb000000, mapped to 0xffffb05a41800000, using 5120k, total 5120k

Exactly the same (save for the mapping) as when I boot Devuan independently of the PCLinuxOS grub2:

[root@devuan groucho]# dmesg | grep vesafb
[    0.645586] vesafb: mode is 1280x1024x32, linelength=5120, pages=0
[    0.645590] vesafb: scrolling: redraw
[    0.645594] vesafb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    0.645612] vesafb: framebuffer at 0xfb000000, mapped to 0xffffad6701800000, using 5120k, total 5120k

So ...
Now I have to see about why this is happening.
And how to get this to be permanent even if it means using the deprecated vga=XXX entry.

Any ideas?

Thanks in advance,

A.

emanym

Member

Registered: 2018-04-08

Posts: 36  

Re: [Solved] Screen output at boot time

So ...
Now I have to see about why this is happening.
And how to get this to be permanent even if it means using the deprecated vga=XXX entry.

That option may not be deprecated in pclinuxos (yet) even if it is in devuan/related dists.

Anyway, grub on devuan recognizes dists based on /usr/lib/os-probes/mounted/90linux-distro and makes a config with /etc/grub.d/30_os-prober.

I'm assuming the pclinuxos grub does something similar, but editing the 30_os-prober file to handle devuan is probably not a great idea... Have a look at it to see what I mean ;-)

You could make a custom entry for devuan (on pclinuxos) in /etc/grub.d/40_custom based on the original menuentry from the pclinuxos grub, with an added vga= option. I assume that would end up last in your grub menu.

Altoid

Member

Registered: 2017-05-07

Posts: 1,581  

Re: [Solved] Screen output at boot time

Hello:

That option may not be deprecated in pclinuxos (yet) even if it is in devuan/related dists.

I have read in a couple of pages I came across while searching for information that it was deprecated but ...

It does not seem to be deprecated in Devuan: I edited the grub2 entry in Devuan, it was picked by when I did grub-upgate from PCLinuxOS and worked perfectly well when I selected to boot Devuan from PCLinuxOS.

But I also tried vga=ask and the screen said that it was a deprecated option.

Anyway, I also discovered something else, the real origin of the problem (and I am rather embarrased about this).

I use grub-customizer (yes, I know ... ) and it happens that when I was booting Devuan from PCLinux's grub2, I was inadvertently selecting a 'custom' entry which I do not have a clue about or where it came from but I now know that update-grub does not modify it.

It's so damn obvious so as to go unnoticed but makes prefect sense: update-grub only modifies the scripts generated by OS prober, a 'custom' script entry remains just that so it stays unchanged. No idea where it came from or when.

Having tried out by editing and then adding vga=845 to the Devuan grub2 (and seen it worked) and seeing that it was not getting picked up by the PCLinux grub2, I started pouring over the grub.conf files and that's when I discovered this uncomfortable tidbit.  =^/

The vga=845 bit is now part of the grub2 command line in Devuan and it does get picked up by the grub2 in PCLinuxOS when I update-grub.
I was just not selecting the correct entry. What a dick ...

... grub on devuan recognizes dists based on /usr/lib/os-probes/mounted/90linux-distro and makes a config with /etc/grub.d/30_os-prober.

I see (sort of): it is what I am saying above?

... editing the 30_os-prober file to handle devuan is probably not a great idea... Have a look at it to see what I mean ;-)

Hmm ...
It took me a good while to sort of understand and get a (light) hold on what was going on, so I'll pass on that. =-)
I'll chalk all this up to experience and a lesson learned.

Irrespectively of this, if vga=XXX is deprecated then there must be a substitute way to do the same thing.

With time, I'll see about trying out different options in grub2: after all, I boot into PCLinuxOS without VGA=XXX, vesafb gets loaded without nokmsboot present and still get the monitor resolution I want using the Nvidia drivers.

I gues I can mark this as [Solved] - hopefully it will be of use to others.

Thank you very much (to all) for your input.

Best,

A.