Question: I have done a lot of Googling and I can't make sense of all the information.

I want to remotely operate a Lubuntu 14.04 machine from another of the same type. The remote machine has no monitor attached. I have Teamviewer10 on both machines.

The problem is that with no monitor attached, the remote desktop has only 1024x768 resolution. xrandr shows LVDS1 to be connected, although it isn't, and it only allows 1024x768 resolution. 

The solution appears to entail using xrandr to test resolution, and then inserting the xrandr commands somewhere to execute the commands on startup/login, and make the change permanent. It is also possible that I need to create /etc/X11/xorg.conf and set up a dummy monitor. I really do not understand the steps entailed in that, and many Googlees say it does not work anyway. Some say I need a hardware dongle (I really cannot believe that you need hardware to do something like this - it must be a common requirement to use a machine without a monitor).

I would be very grateful if somebody could tell me if I am on the right track and make these ideas more concrete. I do not really want to hear about solutions using other remote viewing software (vnc etc). I may try these ideas in the future when I have time, but right now I want to make it work using Teamviewer (because thus far I have found it to be less laggy than other software when some of the screen contains video).

Many thanks.

Answer: 
After a lot of trial and error, I determined the following commands on the remotely controlled machine (the headless machine) will increase the resolution of the screen seen by Teamviewer.

```
xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
xrandr --addmode VIRTUAL1 1920x1080_60.00
xrandr --output VIRTUAL1 --mode 1920x1080_60.00
xrandr --output LVDS1 --off

```

The commands should be executed on the the headless machine when it starts up, but if this cannot be achieved they can be executed from the remote machine using a low resolution connection. The screen can then be set to a higher resolution.
a bit late but here is how I got it to work for Teamviewer 13 (for my own reference mainly)

```
sudo apt install xserver-xorg-video-dummy

```

---

```
sudo nano /etc/X11/xorg.conf

```

---

```
Section "Device"
    Identifier "DummyDevice"
    Driver "dummy"
    VideoRam 256000
EndSection

Section "Screen"
    Identifier "DummyScreen"
    Device "DummyDevice"
    Monitor "DummyMonitor"
    DefaultDepth 24
    SubSection "Display"
        Depth 24
        Modes "1920x1080_60.0"
    EndSubSection
EndSection

Section "Monitor"
    Identifier "DummyMonitor"
    HorizSync 30-70
    VertRefresh 50-75
    ModeLine "1920x1080" 148.50 1920 2448 2492 2640 1080 1084 1089 1125 +Hsync +Vsync
EndSection

```