SABnzbd

SABnzbd is a solid long-time usenet downloader. There are others, but i will focus on this one.

SABnzbd has an ebuild for Gentoo, so installing it it's a simple emerge:

emerge -v sabnzbd
mkdir /data/daemons/sabnzbd
mkdir /data/daemons/sabnzbd/cache
mkdir /data/daemons/sabnzbd/dirscan
mkdir /data/daemons/sabnzbd/admin
mkdir /data/daemons/sabnzbd/backup
chown -R sabnzbd:media /data/daemons/sabnzbd

Edit the default config file /etc/sabnzbd/sabnzbd.ini, the following are the required changes:

sabnzbd.ini

log_dir = /var/log/sabnzbd
admin_dir = /data/daemons/sabnzbd/admin
cache_dir = /data/daemons/sabnzbd/cache
complete_dir = /data/Media/Downloaded # where to put completed downloads 
download_dir = /data/Media/Downloading # where to put incompletes
dirscan_dir = /data/daemons/sabnzbd/dirscan
nzb_backup_dir = /data/daemons/sabnzbd/backup
port = 6789
host_whitelist = home.mydomain.com,

The host_whitelist is important, otherwise you will not be able to login from the reverse proxy.

Add the sabnzbd user to the media group:

usermod -a -G media sabnzbd

You need to do some fine tuning to the /etc/conf.d/sabnzbd file. Put the following content in it:

SABNZBD_CONFIGFILE="/etc/sabnzbd/sabnzbd.ini"
SABNZBD_USER="sabnzbd"
SABNZBD_GROUP="media"

# 0 - error/warnings, 1 - info, 2 - debug
SABNZBD_LOGGING="1"

And setup the downloads and temporary folders:

Before you proceed, you should make SABnzbd web accessible via the reverse-proxy, so that access, configuration and usage will be simplified from the beginning.

Add this file to /etc/nginx/folders:

sabnzbd.conf

# NZB Get
location ~ ^/sabnzbd($|./*) {
        rewrite /sabnzbd/(.*) /$1 break;
        proxy_pass http://127.0.0.1:6789;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
location ~ ^/sabnzbd$ {
        return 302 $scheme://$host$request_uri/;
}

Add the setup to the Reverse Proxy and reload it. Check The Reverse Proxy concept for more details.

Now, setup the daemon to start at boot, and start it now:

rc-update add sabnzbd default
/etc/init.d/sabnzbd start

Every download client needs to be integrated in your other tools. Unfortunately, you need to do it by hand for every tool.

Every *Arr's tool has the same settings → downloaders section that you can populate with the downloaders. Tap on the plus button and add the downloader. Test it before saving.

Prowlarr is a special case: you only need to define the downloader IF you plan to search from the Prowlarr web GUI, otherwise it's not needed. And no, Prowlarr will not synchronize your downloader to the other *Arr's, like it's done for indexers. Sad, but that's the way it is.