Plex Media Server and Removable Media

About a year ago I got a Samsung Smart TV. One of the neat things about this TV is that it can run Apps like Plex. Plex is a client that connects to a corresponding media server, that could run on an old Linux box or Linux NAS.
While the whole world seems to go towards streaming stuff from the cloud (incurring excessive bandwidth charges) and buying terabytes of hard-drives (expensive), there is still a small fraction like me, that embraces on physical media. Especially Blu-Ray seems offers a reliable cost-efficient way to store immutable data (i.e. stuff you never modify) like movies, favourite TV series, etc. Assuming a dual-layer Blu-Rray you can stuff about 25 TB of stuff into a that case. If you buy the BD-R dual-layer in bulk from Japan, you can get them as low as 3$ - 4$ a piece. In terms of long-term storage characteristics, the Blu-Ray runs circles around your regular HDD. Compare that to investing a 25 TB NAS array. As you read this, Panasonic and Sony paired up to release a 300 GB disk by the end of 2015.
Anyways, the assumption to stream from a HDD is baked into many media servers like Plex. The obvious way to fix it hack the server at the OS level. Going back a decade the new kid on the block to do this was autofs in Linux that is still part of many modern distributions. My media server currently still runs Ubuntu 11.04. I could install it using

apt-get install autofs

Once installed it creates five files in /etc:

/etc/auto.master
/etc/auto.misc
/etc/auto.net
/etc/auto.smb

The idea of autofs is the following. Once you touch a directory that points to an external source, autofs tries to mount it. Specifically for my Blu-Ray player I did the following:

#/etc/auto.misc
cdrom -fstype=iso9660,ro,nosuid,nodev :/dev/cdrom

cdrom is the name of the directory to touch in the mount-point directory of autofs, which is declared in:

#/etc/auto.master
#
# Sample auto.master file
# This is an automounter map and it has the following format
# key [ -mount-options-separated-by-comma ] location
# For details of the format look at autofs(5).
#
/vol /etc/auto.misc --timeout 3

In my case I chose /vol which is unmounted after inactivity of 3 seconds. In a nutshell, this boils down to mounting /vol/cdrom if it gets touched. What is left to do is to create the mount-point directory and give it the appropriate permissions. Make sure that the autofs mount-point is not used in: /etc/fstab.

sudo mkdir /vol
sudo chmod 0755 /vol

Now restart the autofs service and try it out.

sudo service autofs restart
ls /vol/cdrom
...

Now the issue left on the table is to instruct the media server to reset its index every time a disk is removed and to re-index every time a disk is inserted. For Plex, I wrote this little script to do the grunt-work. It takes the auto-mount point as first parameter and the id of the collection that points to the drive as second parameter. If it is run and detects a medium, a re-index is triggered. If no media is inserted the index is wiped.

#!/bin/bash
if [ "$#" -ne 2 ]; then
    echo "Illegal number of parameters"
    exit 1
fi

VOL=$1
SECTION=$2

if [ `ls ${VOL} 2> /dev/null | wc -l ` -ge 1 ]; then
 # Make sure only one indexer is running at the same time
 if [ `ps -eadf | grep "Plex Media Scanner" | wc -l` -le 1]; then
  # Index the section
  /usr/lib/plexmediaserver/Plex\ Media\ Scanner --scan --refresh --section ${SECTION} &> /dev/null
 fi
else
 if [ `ps -eadf | grep "Plex Media Scanner" | wc -l` -le 1]; then
  # Wipe the section
  /usr/lib/plexmediaserver/Plex\ Media\ Scanner --reset --section ${SECTION} &> /dev/null
 fi
fi

To run it automatically, you can add it to the crontab of root as follows.

sudo crontab -e
# add the following line
* * * * * su plex -c "/usr/sbin/scan_plex /vol/cdrom 4"

Cron runs this script every minute. So within a full-minute you have your inserted media indexed. Potential extensions are to trigger such a script from udev on auto-mount, or write your own little daemon, but that is a little more complex.