Can't turn my display off

[SunnyCloudy]

Hello,

I have 3 monitors, I use all of them for work, all of them are connected to the work PC via Display Port.
I also have a little proxmox server i recently built and I connected it via HDMI to my right screen.

Issue is, whenever I shutdown my work PC, the screens are going to sleep because they loose signal, that's good, except for the right screen which now automatically switches to HDMI input and stays on forever.

Some info:

• CPU is Intel i5-14500T with integrated GPU
• Don't have a dedicated GPU
• Proxmox installed on ZFS (systemd-boot)
• Linux 6.5.13-3-pve

What I tried:

• Added consoleblank=60 to /etc/kernel/cmdline which tries to turn off display after 60 seconds of inactivity
• Played with the setterm command trying out all the possible combinations of --blank --powersave --powerdown
• Even installed some packages like vbetool and tried other commands without any success
• Booted on an slightly older kernel (Linux 6.5.13-1-pve), same issue
• Reseting BIOS to default, issue still persists
• Disabling CSM support in BIOS (it's disabled by default, can't even enable it witout a dedicated GPU)
• Connecting a windows box on that HDMI cable instead of the proxmox box and confirming that it does in fact put the screen to sleep, so it's not a monitor issue!

Nothing is working, screen will not go to sleep, here's what happens step-by-step:

1. The screen blanks after 1 minute via consoleblank=60 or setterm --blank 1 this is good.
2. After that, the monitor says "scanning for signal...", this is normal.
3. 1 second later it reports "no HDMI signal from your device". Good! This is where it's supposed to go to sleep... but it doesn't
4. Because a split second after, it finds a ghost HDMI signal from Proxmox! But the screen is frozen, cursor isn't blinking.
5. Pressing a key brings it out of the zombiefied state and the cursor starts blinking again (this is when the screen while off should switch back on, but mine never switches off, that's the issue)

I even took a video of it, here -> https://www.youtube.com/watch?v=U357b2IUYAQ


What I haven't tried:

• Playing with CPU governor, this is what I have in journalctl Mar 25 00:28:57 pve kernel: ENERGY_PERF_BIAS: Set to 'normal', was 'performance'
• Playing with APM or ACPI, no clue even where to start (I was going to do some research about this this after I've set everything up on proxmox)

Anybody got any clue what's going on here? I've lost half of day on this browsing forums, overflows, reddit... I haven't found anyone complaining of this behaviour or a solution for it.

Thanks!

 

[SunnyCloudy]

Forgot to mention, I also unplugged everything from the proxmox box.
Except for the:

• HDMI cable
• LAN cable
• Keyboard

 

[plumpychunq]

any update? I'm having the similar problem.

 

[RolandK]

did you try how it behaves with a different monitor model ?

 

[Etienne Charlier]

Your monitor input select might be set to "auto"
selecting diplayport input on your monitor instead of auto might prevent it to "fall back" to your proxmox

 

[plumpychunq]

I'm using an old iMac with a built-in monitor with no physical hardware way to turn it off.
I think I found a solution but I still testing it and I'm not sure how it will handle OS updates.
Here is what I did (probably not the most secure).

Added a systemd service file
# vi /etc/systemd/system/autologin@tty5.service

[Unit]
Description=Autologin on tty5 for root
After=systemd-user-sessions.service

[Service]
ExecStart=-/sbin/agetty --autologin root --noclear tty5 38400 linux
Restart=always
RestartSec=0
Type=idle

[Install]
WantedBy=getty.target

Appended to root's /root/.bashrc file:
# vi /root/.bashrc

# Run setterm if logging in on tty5
if [ "$(tty)" = "/dev/tty5" ]; then
    setterm --blank=1 --powersave powerdown --powerdown=1
fi

Made it a service:
# systemctl enable autologin@tty5.service
# systemctl start autologin@tty5.service

 

[SunnyCloudy]

did you try how it behaves with a different monitor model ?

I don't have another monitor. 2 of them are the same (dell) and the middle one is display port only (gaming 165hz)

Your monitor input select might be set to "auto"
selecting diplayport input on your monitor instead of auto might prevent it to "fall back" to your proxmox

I tried all combinations, believe me. Setting to auto, display port or hdmi, no difference.
When I have a windows box connected to the monitor via HDMI (instead of the proxmox box) and its turning off the display, the monitor just shows as "no signal detected" and then goes to sleep. As soon as I move the mouse or press a key on the windows machine the screen wakes back up. No such thing for the proxmox box, it enters in a zombified state, just like I showed you in the video.

I think I found a solution

So after booting the machine up, the tty1 is showing login page but if somebody switches to tty5 they are automatically logged in as root? that's not a solution, its a major security flaw.

 

[plumpychunq]

I don't have another monitor. 2 of them are the same (dell) and the middle one is display port only (gaming 165hz)


I tried all combinations, believe me. Setting to auto, display port or hdmi, no difference.
When I have a windows box connected to the monitor via HDMI (instead of the proxmox box) and its turning off the display, the monitor just shows as "no signal detected" and then goes to sleep. As soon as I move the mouse or press a key on the windows machine the screen wakes back up. No such thing for the proxmox box, it enters in a zombified state, just like I showed you in the video.


So after booting the machine up, the tty1 is showing login page but if somebody switches to tty5 they are automatically logged in as root? that's not a solution, its a major security flaw.

How can somebody switch to roots TTY session unless they already had root or sudo access?

 

[SunnyCloudy]

with the switch tty shortcut, you don't have to be logged in to switch between ttys

but this is not the point of this topic.