A seedbox is a nice step up from a normal torrent client if you want to get more serious about contributing back to your swarms. I personally run an rtorrent instance on my home Debian server. I’ve automated it to a fair degree, which lets me seed files 24/7. I use this mostly for linux distributions, such as the ArchLinux ISO, so that I can help indirectly contribute to the health of these open source projects.

I see a lot of people set up home services like this in a rather haphazard fashion, running a daemonized process as their administrative user and giving it free reign over their home directory. Isolating processes to their own user is a good security practice, it can help you keep a tidier box and lower your cognitive strain when working with a specific service. Personally, I also find it easier to keep track of everything in one location.

I’m assuming you’re running some variant of Debian on your server. The general setup principles are the same no matter the flavor of linux, so adjust as necessary based on your favorite package manager. To start out, we’ll install some software and add a new user:

sudo aptitude install rtorrent screen
sudo useradd -m rtorrent

This creates a new user named rtorrent, with a default home directory. Note that I didn’t pass the -p flag, leaving this account without a password. This was intentional, because this account shouldn’t ever be logged in to like a normal user. Having no password ensures that the rtorrent user can’t be logged in directly without an SSH key. We’ll be setting things up initially with su, but we can add that ssh key at the end for easy maintenance and monitoring.

Switch to the new user with:

sudo su rtorrent

This is a bit of a workaround but it’ll do for the initial configuration. Change to this user’s home directory with cd, open the file .rtorrent.rc in your favorite editor, and add the following:

download_rate = 0
upload_rate = 0

directory = /home/rtorrent/downloads
session = /home/rtorrent/.rtorrent/session

port_range = 49152-65535
port_random = yes

schedule = watch_directory,5,5,load_start=/home/rtorrent/torrents/*.torrent
schedule = untied_directory,5,5,stop_untied=
schedule = tied_directory,5,5,start_tied=

system.method.set_key = event.download.finished,link_complete,"execute=cp,-r,$d.get_base_path=,/home/rtorrent/finished"

The first 6 configuration options are rather self explanatory. The schedule lines respectively set up where rtorrent should watch for files, that it should start those torrents when they are created, and stop them when they are deleted. Your session folder is where rtorrent stores its internal database that allows it to keep track of torrents persistently. The very last line sets up rtorrent to copy the finished files to a different directory. This specific option lets me know when torrents have finished and lets me copy them to archival media before clearing the temporary folder.

So, now we need to create the necessary folders in the home directory. We can do that with:

mkdir -p downloads torrents finished .rtorrent/session

We also need to tweak a few settings so that rtorrent will work from the normal user account you logged in with. Set the finished and torrents folders group sticky with:

chmod g+s finished torrents

This is known as the “Set Group ID” or SGID bit. Be wary of the difference in sticky bits, as there is also a SUID bit and simply a ‘sticky bit’. All three can be set independently, and do rather different things. Next, Set open group permissions with:

chmod g+rwx finished torrents

This sets both folders as group writable, and the sticky permission ensures that files created within this folder inherit the same group.

Having rtorrent start as the proper user on boot would be really nice, so we’ll create a new file called start_rtorrent.sh. Add the following:

#!/bin/bash
screen -d -m rtorrent

Add executable permissions:

chmod +x start_rtorrent.sh

This script starts screen, executes the command rtorrent and immediately detaches from the session. We still need to add this script to our crontab. To ensure our newly created script is called on system boot, edit rtorrent’s crontab with crontab -e and add:

@reboot /home/rtorrent/start_rtorrent.sh

Next, edit the .bashrc file and add umask 0002. This overrides the rtorrent user’s default umask of 0022, which means new files created by the rtorrent user will have the permissions 775, or rwxrwxr-x. This lets anyone who is part of the rtorrent group to delete files in finished.

We’re all done, take the opportunity (optionally) to add your public key to ~/.ssh/authorized_keys and exit the session. Then, just make sure your normal user is in the rtorrent group with:

sudo usermod -Ga rtorrent username

Now, just create symlinks pointing to ~rtorrent/torrents and ~rtorrent/finished wherever you’d like in your home directory. Drop your torrents in the torrents folder, and wait for the finished download to appear in finished. You can safely delete these downloads and they’ll still be seeding, living in ~rtorrent/downloads. Personally, I access this server over NFS on my home LAN, but you could easily scp torrents or use any other mechanism you’d prefer to get them on the machine.