These are some notes on the design considerations for a script-based
automounter for USB mass-storage devices, including FLASH drives, SD cards
and 'real' hard drives. Multi-card readers are supported.

I wanted something easy to use and easy to administrate by default that
could work as easily as USB storage devices do under Windows or MAC OS.

I started from scratch writing code in a linear fashion as I wasn't sure
what was possible and not. I tried to put myself in the place of a
typical inexperienced user and administrator and use a safe but easy
default behaviour.


A:  Installation should be easy with little configuration required, but
with the possibility to tighten things as needed.

Xusb-hotmount installs as a Slackware package without overwriting any
standard Slackware files and by default the program is unactivated.
For Slackware, simply setting the execute bit on /etc/rc.d/rc.usbwatch
makes the program active.

B:  Initialization and Program execution mode.
 Studying how other systems work, including autofs, usbmount and hotmnt
 shows a variety of modes of usage and interface:

Daemon/Polling:
 Runs some sort of daemon or polling program intermittently in order
 to search for new devices or removed devices
On-Demand/Event-triggered:
 Use hotplug or udev events to trigger actions
On-Request/User-driven:
 Run actions only when a user(or root) runs a program 

C:  Device Detection
 usbmount shows how either udev or hotplug can be used to trigger events.
Obtaining a list of 'eligible' devices/partitions to process is handled
 several ways. With udev 'ls /dev/sd*' is very direct. Looping through
 arbitrary ranges is slower and needless if you have udev. This won't work
 with kernel-2.4 so I use blkid as the partition lister. usbmount uses an
 external program sg_utils (try) to uniquely identify device partitions.
 I've seen other code that
 
 usbmount requires you to manually edit /etc/udev/udev.rules and/or
 /etc/hotplug/usb.agent. (hotmnt requires editing ude.rules also???)
 I found that it was better with hotplug to create a unique 'hook' in
 /etc/hotplug.d/usb. This avoids editing/overwriting standard hotplug files
 and needs no further configuration. Executable files in /etc/hotplug.d/usb 
 with the '.hotplug' extension are executed automatically.
 udev can apparently do the same -instead of editing udev-rules and executable
 script can be placed
 
D:  Mounting of devices

 Mount Options and Default behaviour: