On 07/11/2021 20:39, Mark Knecht wrote:

Hi,
I've been playing with a Raspberry Pi 4 as a utility divice for a
couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the desktop functionality through VNC. I can still ssh X apps, and both
xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

I get that this must be possible as essentially VirtualBox is able
to do this. I wonder if there's a way for mere mortals to do something similar?

I'm guessing the reason there isn't a virtual desktop is because
nobody's logged in AT THE PI and started one!

Just start Xorg over ssh, or plasma-wayland, or whatever. Sorry I don't
(yet) know how to do it, I need to find out because I want to do exactly
the same :-)

Cheers,
Wol

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Hi,
I've been playing with a Raspberry Pi 4 as a utility divice for a
couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the
desktop functionality through VNC. I can still ssh X apps, and both
xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

I get that this must be possible as essentially VirtualBox is able
to do this. I wonder if there's a way for mere mortals to do something
similar?

Thanks,
Mark

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On Sun, Nov 7, 2021 at 3:34 PM Neil Bothwick <neil@digimed.co.uk> wrote:

On Sun, 7 Nov 2021 13:39:34 -0700, Mark Knecht wrote:

I've been playing with a Raspberry Pi 4 as a utility divice for a
couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the desktop functionality through VNC. I can still ssh X apps, and both xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

Try x2go instead of VNC. It uses SSH to establish the connection and
start a desktop session, so there is no need for the user to have a
desktop running on the remote machine beforehand.

Looks interesting. Thanks Neil.

Mark

--- SoupGate-Win32 v1.05
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On Sun, 7 Nov 2021 13:39:34 -0700, Mark Knecht wrote:

I've been playing with a Raspberry Pi 4 as a utility divice for a
couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the desktop functionality through VNC. I can still ssh X apps, and both
xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

Try x2go instead of VNC. It uses SSH to establish the connection and
start a desktop session, so there is no need for the user to have a
desktop running on the remote machine beforehand.


--
Neil Bothwick

Last words of a Windows user: = Why does that work now?

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On Sun, Nov 7, 2021 at 2:04 PM Wol <antlists@youngman.org.uk> wrote:

On 07/11/2021 20:39, Mark Knecht wrote:

Hi,
I've been playing with a Raspberry Pi 4 as a utility divice for a couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the desktop functionality through VNC. I can still ssh X apps, and both xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

I get that this must be possible as essentially VirtualBox is able
to do this. I wonder if there's a way for mere mortals to do something similar?

I'm guessing the reason there isn't a virtual desktop is because
nobody's logged in AT THE PI and started one!

Just start Xorg over ssh, or plasma-wayland, or whatever. Sorry I don't
(yet) know how to do it, I need to find out because I want to do exactly
the same :-)

Cheers,
Wol

Wol,
Yeah, you may be right, although it wasn't what I was thinking. If
I start Xorg over ssh then it's running there but visible here. Then I
need to do some sort of disconnect, leaving it running so X apps can
go on working.

If it was like a true 'virtual monitor' then in my mind it's
running there, not getting displayed on a physical screen, and I
connect to it like it was a real monitor but it would just be a VNC
connection and not some sort of way of leaving X11 hanging, or so I
thought.

I did find this which is more or less what you're suggesting:

https://unix.stackexchange.com/questions/327532/how-to-remotely-log-in-with-full-graphical-desktop-over-x11

Turns out the RP4 OS is doing something different than Ubuntu
running on the RP4. In the case of the RP OS VNC connects but tells me
it cannot display the desktop at this time. In the case of Ubuntu
running on the RP4 VNC just doesn't connect.

If I find a solution I'll check back in. Possibly someone else has
some ideas and we'll get a response in the next few days.

Mark

--- SoupGate-Win32 v1.05
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On Sun, Nov 7, 2021 at 2:04 PM Wol <antlists@youngman.org.uk> wrote:

On 07/11/2021 20:39, Mark Knecht wrote:

Hi,
I've been playing with a Raspberry Pi 4 as a utility divice for a couple of purposes - a backup server for here at home as well as an astrophotography manager to run my camera and mount. So far everything
is fine when I have a monitor attached. I can ssh in and run X apps,
and I can run the VNC client and control the desktop.

What I find, however, is that when I boot the RP4 without the
monitor attached, which I would be doing most all the time, I lose the desktop functionality through VNC. I can still ssh X apps, and both xdpyinfo and xrandr still say the X resolution is 1920 x 1280, but
there doesn't appear to be a real desktop for VNC to latch onto.

I get that this must be possible as essentially VirtualBox is able
to do this. I wonder if there's a way for mere mortals to do something similar?

I'm guessing the reason there isn't a virtual desktop is because
nobody's logged in AT THE PI and started one!

Just start Xorg over ssh, or plasma-wayland, or whatever. Sorry I don't
(yet) know how to do it, I need to find out because I want to do exactly
the same :-)

Cheers,
Wol

It seems so far that it's even a little more onerous than that:

In the case where the monitor is detached at boot two modules are not
loaded - fuse & nvmem_rmem. Other than that the module list appears
identical.

If I ssh into the RP4 when it's running RPi OS (previously called
Raspbian apparently) but with the monitor DISCONNECTED when I boot
then screenfetch says there's no GPU. Plugging in the monitor after
it's booted doesn't change anything:

mark@science:~$ ssh -X pi@192.168.86.84
pi@192.168.86.84's password:
Linux raspberrypi 5.10.63-v7l+ #1459 SMP Wed Oct 6 16:41:57 BST 2021 armv7l

<SNIP>
pi@raspberrypi:~ $ screenfetch -nN
pi@raspberrypi
OS: Raspbian 10 buster
Kernel: armv7l Linux 5.10.63-v7l+
Uptime: 0m
Packages: 2038
Shell: 723
Resolution: 5760x1080
DE: KDE5
WM: KWin
CPU: ARMv7 rev 3 (v7l) @ 4x 1.5GHz [29.6°C]
GPU:
RAM: 61MiB / 7898MiB

pi@raspberrypi:~ $ lspci -vm -k
Device: 00:00.0
Class: PCI bridge
Vendor: Broadcom Limited
Device: Device 2711
Rev: 10
Driver: pcieport

Device: 01:00.0
Class: USB controller
Vendor: VIA Technologies, Inc.
Device: VL805 USB 3.0 Host Controller
SVendor: VIA Technologies, Inc.
SDevice: VL805 USB 3.0 Host Controller
Rev: 01
ProgIf: 30
Driver: xhci_hcd

pi@raspberrypi:~ $

However, booting with the monitor ATTACHED now shows the GPU, or at
least a DRM framebuffer possibly, in screenfetch. The PCI devices are
the same:

pi@raspberrypi:~ $ screenfetch -nN
pi@raspberrypi
OS: Raspbian 10 buster
Kernel: armv7l Linux 5.10.63-v7l+
Uptime: 0m
Packages: 2038
Shell: 935
Resolution: 3840x1080
DE: KDE5
WM: OpenBox
CPU: ARMv7 rev 3 (v7l) @ 4x 1.5GHz [37.9°C]
GPU: vc4drmfb
RAM: 144MiB / 7898MiB
pi@raspberrypi:~ $

pi@raspberrypi:~ $ lspci -vm -k
Device: 00:00.0
Class: PCI bridge
Vendor: Broadcom Limited
Device: Device 2711
Rev: 10
Driver: pcieport

Device: 01:00.0
Class: USB controller
Vendor: VIA Technologies, Inc.
Device: VL805 USB 3.0 Host Controller
SVendor: VIA Technologies, Inc.
SDevice: VL805 USB 3.0 Host Controller
Rev: 01
ProgIf: 30
Driver: xhci_hcd

pi@raspberrypi:~ $

I will repeat this experiment using Ubuntu in a little while to see if
the missing GPU is an OS or hardware thing. In this hardware it looks
like the GPU hardware is behind the PCI bridge.

Still to look into Neil's x2go suggestion.

Mark

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On 08.11.21 17:34, Mark Knecht wrote:

In the case where the monitor is detached at boot two modules are not
loaded - fuse & nvmem_rmem. Other than that the module list appears identical.

At the moment I can't help you to solve this in software but there may
be a hardware solution. There are fake monitor plugs. This is just a
plug without a cable that makes the device think that there is a monitor attached even if there isn't. Search for "HDMI dummy plug" or similar.


Andreas

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On Mon, Nov 8, 2021 at 12:23 PM Andreas Stiasny
<gentoo@lists.stiasny.priv.at> wrote:

On 08.11.21 17:34, Mark Knecht wrote:

In the case where the monitor is detached at boot two modules are not loaded - fuse & nvmem_rmem. Other than that the module list appears identical.

At the moment I can't help you to solve this in software but there may
be a hardware solution. There are fake monitor plugs. This is just a
plug without a cable that makes the device think that there is a monitor attached even if there isn't. Search for "HDMI dummy plug" or similar.

Andreas

Actually, if it works and I have little doubt it does, that's a great solution for my needs. I see Amazon has 1920x1080 plugs but also has
virtual 4K plugs. All under $10.

Thanks!

Mark

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On Mon, Nov 8, 2021 at 1:31 PM Laurence Perkins <lperkins@openeye.net> wrote:

-----Original Message-----
From: Mark Knecht <markknecht@gmail.com>
Sent: Monday, November 8, 2021 11:48 AM
To: Gentoo User <gentoo-user@lists.gentoo.org>
Subject: Re: [gentoo-user] Virtual Desktop with a Virtual Monitor?

On Mon, Nov 8, 2021 at 12:23 PM Andreas Stiasny <gentoo@lists.stiasny.priv.at> wrote:

On 08.11.21 17:34, Mark Knecht wrote:

In the case where the monitor is detached at boot two modules are
not loaded - fuse & nvmem_rmem. Other than that the module list
appears identical.

At the moment I can't help you to solve this in software but there may
be a hardware solution. There are fake monitor plugs. This is just a
plug without a cable that makes the device think that there is a
monitor attached even if there isn't. Search for "HDMI dummy plug" or similar.

Andreas

Actually, if it works and I have little doubt it does, that's a great solution for my needs. I see Amazon has 1920x1080 plugs but also has virtual 4K plugs. All under $10.

Thanks!

Mark

So, I don't use the PI variants with GUI or even with a monitor very often, but as I recall if the HDMI port isn't attached at boot it then disables it to save the video memory.

If you then try to use one of the VNC servers that's designed to share the running X session, you'll find that there isn't a running X session.

But what you should still be able to do is install the "vncserver" command to fire up an X server that isn't attached to the physical output, only the VNC.
You may need to configure it to also start your preferred display manager, etc depending on whether or not the distro you're running does that automatically for you.

If you want to be able to plug in a monitor later though you'll probably need one of the dummy plugs to prevent the output from being switched off and ignored.

LMP

So I don't yet know how they do it but I purchased a copy of a product called StellarMate OS yesterday.

https://stellarmate.com/

It's a Pi variant that is set up to control
astrophotography equipment. It's able to run headless and has a web server
that I can access from Chrome on my main Linux box.

https://drive.google.com/file/d/1I6QYXay6rTy_-CDFQpsQBaSaiyOjNFDJ/view?usp=sharing

Screen resolution drops from 1920x1080 with the monitor attached to
1600x900 headless,
but other than that it appears to work fine. Interestingly the taskbar
across the top isn't
accessible, at least yet, but I can run anything I have an icon on the desktop.

I'll be studying how they do this (although I think the headless
monitor plug is probably the
easiest solution) so if someone (Wol?) wants to work offline, get in touch.

Cheers,
Mark

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