Roholt

udev rules 99-usb-mount-rules

# Warning this mounts only the first partition to the defined place, assuming first partition is 1
KERNEL=="sd[a-z]*1", SUBSYSTEMS=="usb", ACTION=="add", RUN+="/bin/systemctl start automount@%k.service"
KERNEL=="sd[a-z]*1", SUBSYSTEMS=="usb", ACTION=="remove", RUN+="/bin/systemctl stop automount@%k.service"

Add systemd service: automount@.service

[Unit]
Description=Automount usb drive to %i

[Service]
Type=oneshot
RemainAfterExit=true

Environment="MOUNTPOINT=/media/user_data/EXTERNAL"

ExecStart=/usr/bin/mount-usb-drive.sh add %i
ExecStop=/usr/bin/mount-usb-drive.sh remove %i

Add script to filesystem that actually mounts the usb drive:

#!/bin/bash

# First parameter indicates to add or remove drive.
# last parameter indicates the device name.

WATCHDIR="/tmp/swuwatchdir"
mkdir -p ${WATCHDIR}

usage()
{
    echo "Usage: $0 {add|remove} device_name (e.g. sdb1)"
    exit 1
}

function do_mount()
{
    check_mount_state

    # Get formatting of the drive. TYPE
    # "blkid -o udev" option does not work for busybox version of blkid.
    eval $(/sbin/blkid ${DEVICE} | tr " " "\n" | tail -n 1)

    echo "Mounting ${DEVICE} of type ${TYPE} to ${MOUNTPOINT}"

    /bin/mkdir -p ${MOUNTPOINT}

    # Global mount options
    OPTS="rw,relatime,sync"

    # File system type specific mount options
    if [[ ${TYPE} == "vfat" ]]; then
        OPTS+=",users,gid=100,umask=000,shortname=mixed,utf8=1,flush"
    fi

    if ! /bin/mount -o ${OPTS} ${DEVICE} ${MOUNTPOINT}; then
        echo "Error mounting ${DEVICE} (status = $?)"
        /bin/rmdir ${MOUNTPOINT}
        exit 1
    fi

    # Place dummy file in MOUNTPOINT/../mountWatch to not
    # have to watch the entire user directory.
    touch ${WATCHDIR}/asdf
    echo "**** Mounted ${DEVICE} at ${MOUNTPOINT} ****"
}

function do_unmount()
{
    if [[ ! -d ${MOUNTPOINT} ]]; then
        echo "Warning: ${DEVICE} is not mounted"
    else
        /bin/umount -l ${DEVICE}
        echo "**** Unmounted ${DEVICE}"
    fi


    rm ${WATCHDIR}/asdf
    /bin/rmdir ${MOUNTPOINT}
}

function check_mount_state() {
    # See if this drive is already mounted, and if so where
    MOUNTED_TO=$(/bin/mount | /bin/grep ${DEVICE} | /usr/bin/awk '{ print $3 }')
    if [[ -n ${MOUNTED_TO} ]]; then
        echo "Warning: ${DEVICE} is already mounted at ${MOUNTED_TO}"
        echo "We only expect one USB drive to be inserted at a time."
        exit 1
    fi
}

function main() {

    if [[ $# -ne 2 ]]; then
        usage
    fi

    ACTION=$1
    DEVBASE=$2
    DEVICE="/dev/${DEVBASE}"

    # Var MOUNTPOINT should be set by the systemd script. Check it.
    if [[ -z ${MOUNTPOINT} ]]; then
        echo "MOUNTPOINT is not set by systemd script."
        exit 1
    fi

    case "${ACTION}" in
        add)
            do_mount
            ;;
        remove)
            do_unmount
            ;;
        *)
            usage
            ;;
    esac
}

main $@

Based on: https://serverfault.com/questions/766506/automount-usb-drives-with-systemd