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.