Wednesday, March 4, 2015

Mounting Shared Drive on Linux and Headless Bittorent Daemon

There are a number of different ways to automate the download of bittorrent files.  Many bittorrent clients have the ability to "watch" a directory and if a torrent files get added there then the bittorrent will automatically begin to download.  Some even don't need to download the file as it can subscribe to a feed directly.


What I did before was to log into a machine, connect to a shared drive and then open Transmission which was configured to look at the shared drive for any new torrent files.  I even wrote a program that grab checked and downloaded new torrent files every 24 hours.  Setting this up was extremely simple.  As part of my login items on OSX, I had it connected to my shared drive.  Then I would start Transmission and have it point to the shared drive to automatically download the torrents.  I used watch to execute my torrent downloads:

watch -n 72000 <program to download torrents>
I didn't use cron or anything because this was originally on a OSX laptop.

When I switched to a Linux machine that is kept on, I did the exact same thing.  The problem with this is that you're expected to be logged in to the system and keeping the programs running.  If someone else need to use the computer then everything stops since you'd have to log out.

Terminal Way

This similar to the GUI way described above except you do it in a terminal running in a tmux session so that you can disconnect without loosing your transmission job.  To connect to the shared smb drive without the GUI by using transmission-cli tool.

dbus-launch bash
gvfs-mount smb://<user>@<host>/<path-to-shared-drive>
sudo yum install transmission-cli
You'd put in your user name and password as it prompts you when you mount the shared drive.  You'll need to configure transmission.

Headless Way

This doesn't require any GUI or terminal and can automatically starts at each boot.

Install the transmission-daemon

sudo yum install transmission-daemon
sudo systemctl start transmission-daemon.service
sudo systemctl stop transmission-daemon.service
The service file is in /usr/lib/systemd/system/transmission-daemon.service.

I started and stopped the daemon because you need to configure it through the /var/lib/transmission/.config/transmission-daemon/settings.json and this gets created when you first start (for other locations of Transmission files click here).  This will also install the transmission user

Next you need to mount the shared drive in order for transmission to access and ONLY transmission:

sudo mount -t cifs -o -credential=<path-to-credential>,gid=`id -g transmission`,uid=`id -u transmission` <mount point>
The credential value points to a file that contains your username, password and domain for logging into the shared drive.  Make sure wherever you store it that it's not readable by others.

The gid and uid belongs to the user you want to be able to do read-and-writes to the shared drive otherwise it'll only be root that can do it.  For Fedora, the user is "transmission"

If it works and you can read-and-write, you can move this into /etc/fstab:

//<host>/<path-to-file> <mount-point> cifs credentials=<path-to-cred>,uid={user id},gid={group id}
and then reload fstab:

sudo mount -a
Once you configure the /var/lib/transmission/.config/transmission-daemon/settings.json to your liking then fire up:

sudo systemctl start transmission-daemon.service
sudo systemctl enable transmission-daemon.service
This starts up the service now and also at each machine reboot.  The one issue is that transmission-daemon might start before the drive is mounted and then it won't look for the changes.  It needs to be told to wait.

Systemd will look at /etc/fstab and automatically create an unit that can be added to the service file to tell it to wait.  Running the systemctl command will show you an unit that can be used (it'll be something with a .mount suffix).

Add that unit to the After line: <mount unit>

Finally, set up a cron job to regularly check for new torrents:

crontab -u <transmission user> -e
With the value being something like:

0 23 * * * <path-to-program-to-run> >> /var/lib/transmission/download.log 2>&1
which says to execute the program every night at 11pm and store the out put in /var/lib/transmission/download.log.

Since the transmission users is disabled for an interactive shell, to execute commands as the transmission user, use:

sudo -u <transmission user> <command>

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