I have an old laptop set up with mint (what I had a usb laying around for) and running foundryvtt with docker. That's all set up and working great, starts services on reboot, runs headless.
What I would like to do, mainly because I think it would look cool, is have a small CRT screen that I have plugged into the laptop via HDMI to display the performance status with htop, or docker output or something. I can do this with starting a terminal session with the other display plugged in, but this requires user interaction and all of that.
This side of linux is kind of new to me, so I am not sure what direction I need to start looking in. Is it possible to set up a service to run headless and output to a display in a way that automatically comes up if the device is rebooted? Or is it possible to modify my existing docker container to output logs to display?
Appreciate any input to help get me pointed in the right direction.
EDIT: Solved!
Thanks to everyone for pointing me towards getty, grub boot settings, and bash profiles - got a setup that I'm happy with.
I was able to disable the laptop monitor and enable the CRT by adding this to /etc/default/grub
# Disable laptop monitor (LVDS-1) and only output to CRT (HDMI-A-1)
GRUB_CMDLINE_LINUX_DEFAULT="video=LVDS-1:d video=HDMI-A-1:1024x768"
(don't forget sudo update-grub to apply)
I initially set it to 640x480, but display was better with higher res and large font size, which I scales up with sudo dpkg-reconfigure console-setup
I created a service account for this, and set up a systemd service to start getty on that account based on those docs
[Service]
Type=idle
ExecStart=
ExecStart=-/sbin/agetty --skip-login --noreset --noclear --autologin axies - ${TERM}
Then I added htop to the ~/.bash_profile for that user and... done!
Only thing is there is some overscan on the display and initially about 3 rows / cols were cut off on each side. I was able to adjust the CRT display itself to mostly mitigate this, so now only a bit is cut off and it's usable, but it's not perfect. I tried setting the margin in the video options in grub with margin_top, margin_left etc., as per these docs but that didn't work, even though I verified the resolution was applying correctly. But it is functional!
The people here talking about a display server (x11/Wayland) are missing your point I think. If you put a display server on this "box" then it will become a normal server, not a headless one. At that point, you may as well run a full VM and have the output go wherever you want, etc. I'm not sure what the equivalent is in the docker world, but I'm pretty sure that's not what you're asking for.
Is it possible for you to get SSH running on this "server"? If so, you may be able to set it up with an SSH client on the host PC (the laptop?) that is full screen on the CRT/HDMI output?
Maybe I'm misunderstanding as well though. Any headless server I've used in Linux will still give you a TTY on the display. Do you not get that? Someone else mentioned Getty, which is likely the service that is managing that. You should be able to configure Getty to give you a specific tty (e.g. tty9) on a specific output, then configure it either to autologin or to run a script on that tty.
I do get a tty and that works fine if I start it manually. I can also ssh into it while on my local network.
I think what I need to configure is to have it automatically start a tty at boot with specific credentials and auto start whatever monitoring I want. That should work I think. The only downside of that is I don't want it to run on the laptop screen at all, only the hdmi output, so that is where I want to learn more about how all of those display interfaces work on linux so I can configure the service accordingly (I think)
Yeah ok, that makes more sense. Some starting points (arch user by practice, but Mint will have similar interfaces):
${TERM}with something like/bin/sh -c '/bin/htop'.This is great info, thanks! I did some messing around yesterday and got it opening a tty on boot, and disabled the startx so it stays there. I will look into the monitor power stuff too. Thanks!