Xrandr is used to set the size, orientation and/or reflection of the outputs for a screen. It can also set the screen size.
Debian GNU/Linux 7 I have found
xrandr in the package named
xrandr is a tool to work with X server. It will be useless if you boot your OS with text console only and you want to keep it this way.
sudo apt-get update
sudo apt-get install x11-xserver-utils
How to know which package to install?
Check this question and its answers. In one of the answers I have created a basic guide to
xrandr as an example.
How to use
xrandr to change resolution?
First simply invoke:
You will probably see (among other things) some common video resolutions available to you, e.g.:
1360x768 59.8 60.0
You can switch to one of them like this:
xrandr -s 1024x768
Adding custom resolution is also possible. Read this.