This documentation is appropriate for Debian 10 (Buster) and Ubuntu 18.04 LTS.
### Security
We advise to make sure your webserver is secure enough.
For instance you can require authentication through SSH keys and not passwords, install Fail2Ban to block repeated login attempts and block unused ports by installing and configuring a firewall.
Then we need to install [certbot](https://certbot.eff.org/), a tool to ask for free Let's Encrypt HTTPS certificates.
```bash
sudo apt install certbot
```
You can use certbot with web server plugins or manually. See [Certbot's documentation](https://certbot.eff.org/instructions).
### NodeJS
We install the latest NodeJS version by adding NodeSource repos and installing NodeJS:
Head over to [this page](https://github.com/nodesource/distributions/blob/master/README.md#table-of-contents) and follow the instructions for `Node.js v12.x`.
!!! info
Unless stated otherwise, Mobilizon always supports only the latest LTS version of NodeJS.
!!! tip
NodeSource repos only gives updates for a specific version of NodeJS (it doesn't upgrade itself to a new major version). When a new major version of NodeJS is released, you need to remove the old repo and add the new one.
### Yarn
Mobilizon uses [Yarn](https://yarnpkg.com/) to manage NodeJS packages, so we need to install it as well.
Follow the instructions on [this page](https://yarnpkg.com/en/docs/install#debian-stable) to add Yarn's repository and install it.
!!! info
It is also possible to install `yarn` directly with `npm`:
```bash
npm install -g yarn
```.
You need to make sure npm's binary packages folder in your `$PATH` afterwards to use `yarn`.
### Erlang and Elixir
The packages from Debian or Ubuntu are badly packaged and often out of date, so we need to add one final source repository.
Follow the instructions for Ubuntu/Debian on [this page](https://elixir-lang.org/install.html#unix-and-unix-like) to add Erlang Solutions repo and install Erlang and Elixir.
!!! tip
The Erlang package also wants to install an add-on for Emacs for some reason (but it doesn't install Emacs). If you see a warning, nothing to worry about.
### PostgreSQL and PostGIS
Mobilizon uses the [PostgreSQL](https://www.postgresql.org) database, and the PostgreSQL [Postgis](https://postgis.net) extension to store geographical data into PostgreSQL.