PostgreSQL 9.6 should be available on debian stable (Jessie) from "main" area. Install it using apt: `apt install postgresql-9.6`. Make sure that older versions are not installed, debian allows multiple versions to coexist but still runs only one version.
You must install elixir 1.4+ from elixir-lang.org, because Debian repos only have 1.3.x version. You will need to add apt repo to sources.list(.d) and import GPG key. Follow instructions here: https://elixir-lang.org/install.html#unix-and-unix-like (See "Ubuntu or Debian 7"). This should be valid until Debian updates elixir in their repositories. Package you want is named `elixir`, so install it using `apt install elixir`
Elixir will also require `make` and probably other related software for building dependencies - in case you don't have them, get them via `apt install build-essential`
NodeJS is available as `nodejs` package on debian. `apt install nodejs`. Debian stable has 4.8.x version. If that does not work, use nodesource's repo https://github.com/nodesource/distributions#deb - version 5.x confirmed to work.
* Open psql shell as postgres user - while being root run `su postgres -c psql`
* There, enter following: `ALTER USER postgres with encrypted password '<PASSWORD>';` - where <PASSWORD> is just any string, no need to manually encrypt it, postgres will encrypt it automatically for you.
don't forget to revert it in the later step so you won't have to enter password when accessing psql console.
* Create and update your database with `mix ecto.create && mix ecto.migrate`. If it gives errors, try running again, this is a known issue.
* Undo changes you made in `/etc/postgresql/9.6/main/pg_hba.conf` (replace `md5` with `peer`)
* You most likely don't want having some application accessing database as superuser, so you need to create separate user for that. Right now it must be done manually (issue #27).
* The common and convenient way for adding HTTPS is by using nginx as reverse proxy. You can look at example nginx configuration in `installation/pleroma.nginx`. If you need TLS/SSL certificates for HTTPS, you can look get some for free with letsencrypt: https://letsencrypt.org/
On debian you can use `certbot` package and command to manage letsencrypt certificates.
* (not tested with reboots yet!) You'll also want to set up Pleroma to be run as a systemd service. Example .service can be found in `installation/pleroma.service` you can put it in `/etc/systemd/system/`.
Start pleroma by running `service pleroma start`
Logs can be watched by using `journalctl -fu pleroma.service`