add a simpler motd tutorial

This page is long! This first section hopes to get

you running with a simple task quickly.

## Adding an "message of the day" (motd) on a server

To post announcements to shell users of a servers, it might be a good

idea to post a "message of the day" (`/etc/motd`) that will show up on

login. Good examples are known issues, maintenance windows, or service

retirements.

This change should be fairly inoffensive because it should affect only

a single server, and only the `motd`, so the worst that can happen

here is a silly motd gets displayed (or nothing at all).

Here is how to make the change:

 1. To any change on the Puppet server, you will first need to clone

    the git repository:

        git clone pauli.torproject.org:/srv/puppet.torproject.org/git/tor-puppet

    This needs to be only done once.

 2. the messages are managed by the `motd` module, but to easily add

    an "extra" entry, you should had to the Hiera data storage for the

    specific host you want to modify. Let's say you want to add a

    `motd` on `perdulce`, the current `people.torproject.org`

    server. The file you will need to change (or create!) is

    `hiera/nodes/perdulce.torproject.org.yaml`:

        $EDITOR hiera/nodes/perdulce.torproject.org.yaml

 3. Hiera stores data in YAML. So you need to create a little YAML

    snippet, like this:

        motd::extra: |

           Hello world!

 4. Then you can commit this and *push*:

        git commit -m"add a nice friendly message to the motd" && git push

 5. Then you should login to the host and make sure the code applies

    correctly, in dry-run mode:

        ssh -tt perdulce.torproject.org sudo puppet agent -t --noop

 6. If that works, you can do it for real:

        ssh -tt perdulce.torproject.org sudo puppet agent -t

On next login, you should see your friendly new message. Do not forget

to revert the change!

The next tutorial is about a more elaborate change, performed on

multiple servers.

## Adding an IP address to the global allow list

In this tutorial, we will add an IP address to the global allow list,