Hi,


I'm hoping this is the right place, I'm guessing you server guys have lots of experience with headless setups like this. Maybe not quite correct, though, let me know if it's not.



I'm working with Ubuntu 16.04 LTS on an embedded device (Nvidia Arm arch).

The device has an HDMI output, which we will sometimes (but not always) stream to via gstreamer + nvoverlaysink or direct fb access.

Otherwise, the device has no traditional I/O per-se (kb/mouse/monitor), it operates internally with background services and via ethernet.


The problem I'm having is that when you plug in HDMI and boot the device it shows the console output + login. I don't want it to show anything here, just black screen (or image is fine). Can't hard disable HDMI in the device tree because we need to use it on occasion as described above, but otherwise just want it to be neutral (black, logo, picture, etc.) basically just don't want them to see text + login).

The other thing is that I need the pts accessible for SSH. While not the primary use case, it happens often to the units before they go to customers.

I found a few options, none really work. We can change the printk or log level behavior to lighten the prints, but:
A. You can still have prints
B. It still shows login prompt
C. I'd like dmesg to still be accessible to grab logs (a service does this)


I feel like there's some command line options I could pass to the kernel in extlinux.conf, but I don't see how I could disable just the console via that (opposed to just 'quiet' option). Also I don't believe quiet will kill the login prompt.


Tried disabling console switching in XOrg, but that I guess only disables switching, because main console still works. I also believe that wouldn't do what I want even if I could disable it in XOrg because there's plenty of console prints at boot-up before X server even starts which I'd also like to silence.


Also found the active_consoles in /etc/default/console-setup, but that seems to be just configuration, not the actual TTY creation.


If I can enable/disable the HDMI on the fly (where it starts-up disabled, so no output) that could work, then it could simply be enabled before streaming & disabled when finished. Kind of clunky, but could work.


Does anybody have any ideas?

I stumbled on this post:
https://unix.stackexchange.com/quest...ebuffer-device

Seems the console is drilled straight into the kernel. Definitely not going to be trivial to stop it.


From that then I guess the solution would have to involve enabling / turning on HDMI as a whole prior to displaying the HDMI output, then disabling it / turning it off as a whole after it's finished.

Any thoughts on the matter is still appreciated.