Re: Working on a usb-storage hotplug script

[Wout Mertens <wmertens@cisco.com>]

Yesterday at 17:09, Olaf Hering ponderously produced:

>  On Tue, Dec 09, Wout Mertens wrote:
>
> > Comments?
>
> forget 2.4, work on 2.6. 2.6 will give you a block event if there is
> something of interrest.

Well, you're right. I just created a hotplug script that will automount
all block devices that get attached. I use this behaviour to use a USB
key as a token for connecting to a VNC session from a thin client.

It's way cleaner than the 2.4 version...

Here's the script, comments?

=====================#!/bin/sh
#
# Automount hotplugged block devices, by Wout Mertens.
#
# Linux v2.6 version
# This script is released under version 2 of the GPL.

# To install this, either make it /sbin/hotplug, or, if you have
# linux-hotplug installed, make it /etc/hotplug.d/block/automount.hotplug .
# It needs to be executable. I tested it with busybox's ash.
#
# The devices will be mounted for the console user if applicable.
#
# To work, this needs:
# - v2.6 kernel support:
#   - hotplugging, /proc mounted, /sys mounted
#   - filesystems that will be mounted, like vfat
# - sh, echo, tr, stat or ls, getent or grep passwd,
#   mount, umount, mkdir, rmdir. logger is used if there.
#
# Possible improvements:
# - Create a desktop entry for the device.
# - Call a notifier script when mounting/unmounting. This could create the
#   desktop entry by itself.
# - Mount as supermount if available. This will improve behaviour for
#   synchronous writes and hanging mounts, although umount -lf already
#   does a good job.
# - Detect filesystem on device, so filesystems that don't need a mounting
#   user can skip user detection.

# Debugging
# set -xv
# exec > /tmp/hotplug.$$ 2>&1

PATH="/bin:/sbin:/usr/bin:/usr/sbin"
export PATH

# We only handle block device messages
[ "$1" != "block" ] && exit 0

# Proclaim stuff to the world
mesg () {
	logger -t $0 "$*"
}

# Is path already mounted?
is_path_mounted () {
	while read dev path rest
	do
		if [ "$path" = "$1" ]
		then
			return 0
		fi
	done < /proc/mounts
	return 1
}

# Get mounted path for a device
get_mounted_path () {
	while read dev path rest
	do
		if [ "$dev" = "$1" ]
		then
			echo "$path"
			return 0
		fi
	done < /proc/mounts
	return 1
}

# Wait for a file to appear
wait_for () {
	local count=0
	while [ $count -lt 10 ] && [ ! -e "$1" ]
	do
		sleep 1
	done
	[ $count -eq 10 ] && return 1
	return 0
}

# Remove strange characters from a filename
clean_filename () {
	echo $1 | tr " /?*\"<>" "_______"
}

# Figure out the device to mount
set `echo $DEVPATH | tr / " "`
[ $# -ne 3 ] && exit 0
DEVICE=/dev/$3

if [ "$ACTION" = "remove" ]
then
	# Unmount it
	dir=`get_mounted_path $DEVICE`
	[ -d "$dir" ] || exit 1
	umount -lf "$dir"
	rmdir "$dir"
	exit 1
fi

if [ "$ACTION" = "add" ]
then
	# Mount it

	# Make sure we have support for vfat
	modprobe -q vfat

	wait_for /sys/$1/$2/device/vendor || exit 1

	# Find the name
	PRODUCT=`cat /sys/$1/$2/device/model`
	if [ -z "$PRODUCT" ]
	then
		PRODUCT=generic
	fi
	# Find out where we mount it
	MOUNTPATH=/mnt/usb/`clean_filename "$PRODUCT"`
	if is_path_mounted "$MOUNTPATH"
	then
		count=1
		while is_path_mounted "${MOUNTPATH}_${count}"
		do
			count=$(( $count + 1 ))
		done
		MOUNTPATH="${MOUNTPATH}_${count}"
	fi
	# Make sure it's a directory
	if [ -e "$MOUNTPATH" ]
	then
		if [ ! -d "$MOUNTPATH" ]
		then
			mesg "$MOUNTPATH exists but is not a directory"
			exit 1
		fi
	else
		mkdir -p "$MOUNTPATH"
		if [ $? -ne 0 ]
		then
			mesg "Could not create mountpoint $MOUNTPATH"
			exit 1
		fi
	fi
	# Find out who we are going to mount it as
	CONSOLEUSER=`stat -c%U /dev/console 2>/dev/null`
	if [ -z "$CONSOLEUSER" ]
	then
		set `ls -l /dev/console`
		CONSOLEUSER=$3
	fi
	[ -n "$CONSOLEUSER" ] || CONSOLEUSER=root
	PASSWD=`getent passwd $CONSOLEUSER 2>/dev/null`
	if [ -z "$PASSWD" ]
	then
		PASSWD=`grep "$CONSOLEUSER" /etc/passwd||grep root /etc/passwd`
	fi
	if [ -z "$PASSWD" ]
	then
		mesg "Could not get password entry for $CONSOLEUSER"
		exit 1
	fi
	set `echo $PASSWD | tr : " "`
	if [ $# -lt 4 ]
	then
		mesg "Bad password entry for $CONSOLEUSER"
		exit 1
	fi

	# These options should prevent abuse and make it writeable for the
	# console user.
	MOUNTOPTS="-s -osync,nosuid,umask\a7,uid=$3,gid=$4"
	mesg Mounting $DEVICE on $MOUNTPATH, options $MOUNTOPTS

	mount $MOUNTOPTS $DEVICE $MOUNTPATH
fi
=====================

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