USB flash drives automatically mounted (headless computer)

Question

For the project SamplerBox, up to now I was using /dev/sda1 /media auto nofail 0 0 to have USB flash drives automatically mounted when inserted on the headless computer, see also Auto-mount and auto-remount with /etc/fstab. But this seems not very reliable, for example, when an USB flash drive is removed, and then re-inserted.

What lightweight and easy-to-configure solution is available in Debian to automatically mount every /dev/sd* device to /media/?

• If a second flash drive is plugged, ignore or mount to another folder /media2/

• If a drive is removed (even without a proper umount), and then re-inserted a few minutes later it should be mounted again

The use case is a headless device on which the end user can plug USB flash drives, and it should be always recognized (no matter if they removed the previous USB flash drive without asking permission in the software).

Answer 1

Based on @FelixJN's comment, I slightly modified this excellent guide by Andrea Fortuna according to my needs and here is the solution:

1. Create a file /root/usb-mount.sh containing this (and add +x permission):

   #!/bin/bash
   ACTION=$1
   DEVBASE=$2
   DEVICE="/dev/${DEVBASE}"
   MOUNT_POINT=$(/bin/mount | /bin/grep ${DEVICE} | /usr/bin/awk '{ print $3 }')  # See if this drive is already mounted
   case "${ACTION}" in
       add)
           if [[ -n ${MOUNT_POINT} ]]; then exit 1; fi          # Already mounted, exit
           eval $(/sbin/blkid -o udev ${DEVICE})                # Get info for this drive: $ID_FS_LABEL, $ID_FS_UUID, and $ID_FS_TYPE
           OPTS="rw,relatime"                                   # Global mount options
           if [[ ${ID_FS_TYPE} == "vfat" ]]; then OPTS+=",users,gid=100,umask=000,shortname=mixed,utf8=1,flush"; fi     # File system type specific mount options
           if ! /bin/mount -o ${OPTS} ${DEVICE} /media/; then exit 1; fi          # Error during mount process: cleanup mountpoint
           ;;
       remove)
           if [[ -n ${MOUNT_POINT} ]]; then /bin/umount -l ${DEVICE}; fi
           ;;
   esac
   

2. Create a file /etc/systemd/system/[email protected] containing:

   [Unit]
   Description=Mount USB Drive on %i
   
   [Service]
   Type=oneshot
   RemainAfterExit=true
   ExecStart=/root/usb-mount.sh add %i
   ExecStop=/root/usb-mount.sh remove %i
   

3. Create a file /etc/udev/rules.d/99-local.rules containing:

   KERNEL=="sd[a-z][0-9]", SUBSYSTEMS=="usb", ACTION=="add", RUN+="/bin/systemctl start usb-mount@%k.service"
   KERNEL=="sd[a-z][0-9]", SUBSYSTEMS=="usb", ACTION=="remove", RUN+="/bin/systemctl stop usb-mount@%k.service"
   

4. Restart the rules:

    udevadm control --reload-rules
    systemctl daemon-reload
   

5. Plug a USB flash drive. It should be mounted to /media/.