udev affects behavior of script, prevents dpkg from working

Question

I have a udev rule configured to run a shell script whenever a USB flash drive is inserted; I've verified that udev matches against the rule, that the shell script runs as intended when run manually with the correct parameter, and that the script is being run; it successfully mounts the drive and gets to the point where dpkg should be run, but nothing is actually installed.

Also frustrating my efforts is that I have both dpkg and the script itself set to redirect their output to temp files so I can debug this; however, while both display their output perfectly when run manually, they produce completely empty files when triggered by udev, so I can't even see what error dpkg might be producing, if it's making one at all. I've heard that udev doesn't run things with a terminal, but I don't know if that's the case or if that would cause this.

udev rule:

SUBSYSTEMS=="usb", KERNEL=="sd?1", RUN+="/usr/local/sbin/updater-runner.sh %"

Script being run directly by udev:

#!/bin/sh

/usr/local/sbin/updater.sh ${1} & > /tmp/updater.out`

Main script:

#!/bin/sh

DEVICE=$1
echo "Running..."
echo $DEVICE
# check input
if [ -z "$DEVICE" ]; then
    exit 1
fi

# test that the device isn't already mounted
device_is_mounted=`grep ${DEVICE} /etc/mtab`
if [ -n "$device_is_mounted" ]; then
    echo "error: seems /dev/${DEVICE} is already mounted"
fi

# pull in useful variables from vol_id, quote everything Just In Case
# eval `blkid /dev/${DEVICE} -o value | sed 's/^/export /; s/=/="/; s/$/"/'`

ID_FS_LABEL=$(blkid /dev/${DEVICE} -o value | head -n 1)
export ID_FS_LABEL
ID_FS_TYPE=$(blkid /dev/${DEVICE} -o value | tail -n 1)
export ID_FS_TYPE
echo $ID_FS_LABEL
echo $ID_FS_TYPE
if [ -z "$ID_FS_LABEL" ] || [ -z "$ID_FS_TYPE" ]; then
    echo "error: ID_FS_LABEL is empty! did vol_id break? tried /dev/${DEVICE}"
    exit 1
fi

# test mountpoint - it shouldn't exist
if [ ! -e "/media/${ID_FS_LABEL}" ]; then
    # make the mountpoint
    mkdir "/media/${ID_FS_LABEL}"

    # mount the device

    case "$ID_FS_TYPE" in

        vfat) mount -t vfat -o sync,noatime,uid=1000 /dev/${DEVICE} "/media/${ID_FS_LABEL}"
            ;;

        ntfs) mount -t auto -o sync,noatime,uid=1000,locale=en_US.UTF-8 /dev/${DEVICE} "/media/${ID_FS_LABEL}"
            ;;

        ext*) mount -t auto -o sync,noatime /dev/${DEVICE} "/media/${ID_FS_LABEL}"
            ;;
    esac

    #check if file exists

    #run dpkg
    if [ -f "/media/${ID_FS_LABEL}/ACS.deb" ]; then
        echo "Killing ACS..."
        killall ACS
        echo "Running dpkg..."
        yes | dpkg --force-architecture --force-depends -i "/media/${ID_FS_LABEL}/ACS.deb" > /tmp/dpkg.out
        echo "Restarting ACS..."
        nohup ACS &> /dev/null &
    fi
fi

exit 0

Answer 1

Not sure about the rest of it but the reason you are getting empty files is that you have a syntax error in your script:

#!/bin/sh

/usr/local/sbin/updater.sh ${1} & > /tmp/updater.out`

should be (you should also capture STDERR):

#!/bin/sh

/usr/local/sbin/updater.sh ${1} > /tmp/updater.out 2>/tmp/updater.error &

The way you have it, the script is put in the background before any output is generated and you get empty files. Also, I assume the ` at the end of the line is a typo right?

As for the rest, what user is this being run as? I don't know enough about udev to guess. Does whoever the script is run as have the rights to execute dpkg?