I use my old computer as an NAS, so I remove the monitor after I installed linux on it (disconnect vga cable). I use ssh to control the machine and it works fine. Until some day, after kernel/softare upgrade or messing up some configs, I cannot connect to it through ssh, then I have to plug the monitor back, but the monitor says "No input signal". So I have to restart the computer WITH the monitor connected, and the monitor's back!
I think the computer/linux kernel doesn't detect the monitor plug-in event. So how can I start my linux box without a monitor, but when it goes wrong I can still plug my monitor (vga) back and use the console.
Edit: just one pci-e video card, has dvi, vga, tv/out (s-video)
Edit2: Xorg is not running. I just need the console (CTRL+ALT+F1). The problem is, if the machine booted without a monitor connected, it won't give me a pseudo terminal after I attach the vga cable while it's running. Clearly the monitor is not auto detected as usb device. I'm wondering how to let the monitor auto detected.
Best Answer
This maybe years too late however I was coming across the same issue when I ran into this question but no suitable answer has been given, and I imagine other people having the same problem have came across this question as well.
My fix that seems to work brilliantly is to trick the kernel into thinking a VGA is already connected by adding a kernel parameter (this might be specified in the grub configuration file) which is
video=VGA-1:e
the video parameter could be specified more than once for the kernel so if you already have a video= parameter then just add a new video= parameter (unless of course the existing parameter you believe would conflict with the above fix)