The answer depends on whether you are running X (a current generation gui desktop) or not. You didn't specify.
There are several ways to handle this.
The most precise/limited way is to use
xmodmap. I haven't used it, so I'm not familiar with the details. It will remap keys with specific key codes to specific key symbols.
If you have trouble sorting things out, run
xev. When you press any key combination (or do other X things),
xev will tell you what the system saw which will give you the values you need for
Once you get the command to work, you can run it from your
~/.login script so it's there when you start an interactive shell. Or, you can add it as a bash script into your desktop environment's autostart system.
If you want to do more, you may want to check out
AutoKey which is a desktop automation tool. Among other things, you can define a macro which will be triggered by a simple or compound keypress which can do anything from just emitting another keypress to running a complex macro coded in Python which can do almost anything you can think of - if you know enough Python.
I use it every day and love it.
For simpler things along the same lines, check out
xdotool. It can also do a few things which
AutoKey currently can't do - like emit mouse events.
Not running X (server installation, etc.):
This is a lot harder to find information on because it's a much less common case.
I've never tried it, but I did find some information on it here yesterday answering another question.