Proposed addition to automatically mount usb-storage devices

[Andrew Robinson <awrobinson@cox.net>]

I'd like to offer this script as an addition to the hotplug system. It 
is a wrapper script for updfstab that mounts whatever updfstab adds to 
the /etc/fstab file. It also creates a remover script so that the device 
will be unmounted when it is unplugged.

The motivation for this script was an external USB drive I wanted to use 
on my Fedora Core 1 system. After reading as much documentation as I 
could tolerate, I figured out how to add the device to the 
/etc/updfstab.conf file. However, I could not get it to automatically 
mount. Greg Kroah-Hartman was kind enough to answer my query on this 
list. He suggested devlabel. devlabel does have an automount feature, 
but appeared to require an existing entry in the /etc/fstab file. This 
did not seem to honor the "true spirit" of hotplugging. I tried to get 
devlabel and updfstab to work together with no luck. A message on the 
Fedora mailing list suggested the user mode script, usb-storage in this 
case. I could not get it to work, and reading through the usb.agent 
script (and hotplug.functions), I saw that the usb-storage was executed 
before updfstab.

It seemed I was left with creating my own solution. Since updfstab is 
where I wanted to get the device to mount, that seemed to be the 
opportunity for a wrapper script. There are two other advantages to this 
approach. First, updfstab is called only in the special case of 
usb-storage, so the wrapper script would not disturb any other parts of 
the hotplug system. Second, the wrapper script does not require any 
additional configuration information. It responds to changes made by 
updfstab. I envision eventually a configurator that pops up the first 
time a device is plugged in. The configurator would ask the user if 
he/she would like the device mounted this time and automatically in the 
future. The configurator would then make the appropriate changes to the 
/etc/updfstab.conf file.

Given that this is the first time I've attempted to contribute to a 
development project and given the minutes and minutes I put into 
studying the problem, I would not be surprise if the answer I get back 
is along the lines of "Andrew you ignorant slut. If you had known this 
and looked at that, then you would see the correct way to do accomplish 
this is this." My one request is that you please be constructive in your 
criticism. :)

Thanks!

Andrew Robinson

###############################################################

updfstab.wrapper script:

#!/bin/bash
#
# updfstab.wrapper - monitor additions to the /etc/fstab file made
# by updfstab and mount those filesystems. In addition, create
# the remover file so that those filesystems can be unmounted
# later.
#
# HISTORY:
#
# 10-May-2004  Initial version by Andrew Robinson.
#
# $Id$

# Import the hotplug.functions file to enable use of the log
# messaging routine

cd /etc/hotplug
. ./hotplug.functions
#export DEBUG=yes

# Grab the mount point for each entry in the /etc/fstab file. Skip
# comments and blank lines

FSTAB_BEFORE=$(awk '/^#/ {next}; /^[ ]*$/ {next}; {print $2}' /etc/fstab)
debug_mesg "FSTAB_BEFORE: $FSTAB_BEFORE"

# Run updfstab.

if [ -x /usr/sbin/updfstab ]
then
     /usr/sbin/updfstab
else
     mesg "Cannot find updfstab program."
     exit
fi

# Create a similar list of entries after updfstab has manipulated
# the fstab file.

FSTAB_AFTER=$(awk '/^#/ {next}; /^[ ]*$/ {next}; {print $2}' /etc/fstab)
debug_mesg "FSTAB_AFTER: $FSTAB_AFTER"

# Compare the two lists to find any additions after updfstab has run.

FSTAB_DIFF=""
for elem in $FSTAB_AFTER
do
     if [ $(echo $FSTAB_BEFORE | grep -c $elem -) -eq 0 ]
     then
         FSTAB_DIFF="${FSTAB_DIFF}${elem} "
     fi
done
debug_mesg "FSTAB_DIFF: $FSTAB_DIFF"

# If there are no differences, bail

if [ "$FSTAB_DIFF" = "" ]
then
     mesg "No changes to be made"
     exit
fi

# Insure that the directory for the remover script exists

if [ ! -d $(dirname $REMOVER) ]
then
     mkdir -p $(dirname $REMOVER)
fi

# Create the remover file

echo "#!/bin/bash" > $REMOVER
echo ". $HOTPLUG_DIR/hotplug.functions" >> $REMOVER

# Attempt to mount the new mountpoints. Also add the new
# mountpoints to the remover file.

for mountpt in $FSTAB_DIFF
do
     mesg "mounting $mountpt"
     mount $mountpt
     echo "mesg \"unmounting $mountpt\"" >> $REMOVER
     echo "umount $mountpt" >> $REMOVER
done

# Make the remover file executable

chmod u+x $REMOVER

###############################################################

Changes to hotplug.functions to run updfstab.wrapper:

From:

if echo "$MODULE" | grep -q "usb-storage" > /dev/null 2>&1 ; then
     [ -x /usr/sbin/updfstab ] &&  /usr/sbin/updfstab
fi

To:

if echo "$MODULE" | grep -q "usb-storage" > /dev/null 2>&1 ; then
     if [ -x $HOTPLUG_DIR/updfstab.wrapper ]; then
         $HOTPLUG_DIR/updfstab.wrapper
     elif [ -x /usr/sbin/updfstab ]; then
         /usr/sbin/updfstab
     fi
fi






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