Mounts and unmounts a USB drive based on the presence of another machine in the network. A little more explanation on what it does: http://justcurious.is/2013/raspberry-pi-and-external-drives/

automounter.sh

#!/bin/bash

host="island1.local"
mountPoint="/media/KRETA"
drive="/dev/sda1"
device="/dev/sda"

hostIsUp=-1

checkHostIsUp()
{
  
    ping -q -c 1 $host >> /dev/null
    if [ "$?" -eq 0 ]; then
  hostIsUp=1
    else
	hostIsUp=0
    fi
}

driveIsMounted=-1
checkDriveIsMounted()
{
    if grep -qs $mountPoint /proc/mounts >> /dev/null; then
	driveIsMounted=1
    else
        driveIsMounted=0
    fi
}

doMountDrive()
{
    sh -c 'AUTHFILE="/sys/bus/usb/devices/1-1.2/authorized" ; echo 0 > "$AUTHFILE" ; sleep 1 ; echo 1 > "$AUTHFILE"'
    sleep 10
    mount -t vfat $drive $mountPoint
}

doUnmountDrive()
{
    udisks --unmount $drive
}

doDisconnectDrive()
{
    udisks --detach $device >> /dev/null
}

checkHostIsUp
checkDriveIsMounted

if [ "$hostIsUp" == 1 ] 
then
    echo "host is up"
    if [ "$driveIsMounted" == 0 ] 
    then
        doMountDrive
	echo "mounted drive"
    else
	echo "host is available. drive already mounted."    
    fi
else
    echo $hostIsUp
    echo "host not up"
    if [ "$driveIsMounted" == 1 ] 
    then
        doUnmountDrive
        doDisconnectDrive
        echo "unmounted drive successfully"

    else
	   echo "host not available. drive is not mounted." 
    fi
fi

exit 0