run a script when a device is mounted

1. Make sure udev-automount is installed
   

   pacman -Sy udev-automount

2. Work out udev rules with udevadm (see Arch Wiki - udev)

   udevadm info -a -n /dev/sdc

3. Create a udev rule file based on step 2, e.g. /etc/udev/rules.d/81-sdcard-sync.rules, with contents like this:
   

   KERNEL=="sd?1", ATTRS{idVendor}=="0781", ATTRS{idProduct}=="a7a8", ATTRS{serial}=="6333011111B1", RUN+="/usr/bin/sd-card-sync-start.py"