This provides an input database for typing Pali. The method used is Velthuis, which is a way to write Pali using the limited ASCII character set.
The mapping is as follows:
AA -> Ā
aa -> ā
II -> Ī
ii -> ī
UU -> Ū
uu -> ū
"N -> Ṅ
"n -> ṅ
.M -> Ṃ
.m -> ṃ
~N -> Ñ
~n -> ñ
.T -> Ṭ
.t -> ṭ
.D -> Ḍ
.d -> ḍ
.N -> Ṇ
.n -> ṇ
.L -> Ḷ
.l -> ḷ
IBus is an input method framework used by many GNU/Linux distributions. It provides a system-wide method for typing a language for which you don't have keys on your keyboard. Here are some instructions for getting this system to work with Pali.
Modern distributions will probably already come with IBus pre-installed, in which case you can skip this step.
On debian-like systems (including ubuntu) installing IBus is accomplished by installing the ibus and ibus-m17n package:
sudo apt-get install ibus ibus-m17n
IBus by itself does nothing. It is just a daemon to help applications perform complex input. In order to actually make use of it, you'll need some extra packages depending on your particular window manager and the like. For myself, I had to install ibus packages for gtk and clutter to get my gnome desktop to work properly:
sudo apt-get install ibus-gtk ibus-gtk3 ibus-clutter
Again though, modern distros will most likely come with all required packages pre-installed already.
Other distros will have other but similar ways of installing packages.
Create the directory .m17n.d/ in your homedir if it isn't already there:
mkdir -p ~/.m17n.d
Copy the pali-velthuis.mim file into the ~/.m17n.d/:
cp pali-velthuis.mim ~/.m17n.d/
Log out and back in to ensure the file gets picked up by the system.
You should now be able to add "Pali (velthuis (m17n))" as an input source. The exact way to do this will depend on your desktop environment. In Gnome, you can do so under Settings -> Region & Language.
Depending on your desktop environment, you should now have a language/keyboard picker where you can set your input to Pali. For example, in Gnome, this menu will show up in the top right corner, and you should also be able to switch using the Super-spacebar key combination. (On many keyboards, the Super key is the one with the windows logo).
You should now be able to type "aa" and get "ā".
It looks like IBus doesn't really play well with Emacs, getting in the way of various keybindings, at least with this particular database. If you wish to input Pali into Emacs, I recommend using emacs-pali-velthuis instead. This uses Emacs' own internal input method, and therefore plays much more nicely with the rest of emacs.