Auto mounting a USB drive in a Raspberry Pi

Last Updated on November 29, 2021.

When I’m building some retro arcade setups on a Raspberry Pi I’m often copying over some set of disk images, media files, configuration, or ROMs. They’re not always on the same network, and sometimes it’s just easier to take a keychain thumb drive and copy some files around. I’m not always in a windows environment on these boxes, either. I searched the web for a bit on how to do it and here’s the information I’ve compiled in a step by step format.

Step 1 – Install pmount

pmount is a wrapper around the standard mount program which permits normal users to mount removable devices without a matching /etc/fstab entry. This is how we’ll manage to auto mount our USB drives.

sudo apt install pmount

Step 2 – UDEV Rule

Udev allows for rules that specify what name is given to a device, regardless of which port it is plugged into.

sudo vi /etc/udev/rules.d/usbstick.rules

ACTION=="add", KERNEL=="sd[a-z][0-9]", TAG+="systemd", ENV{SYSTEMD_WANTS}="usbstick-handler@%k"

Step 3 – Create Systemd service

sudo vi /lib/systemd/system/usbstick-handler@.service

[Unit]
Description=Mount USB sticks
BindsTo=dev-%i.device
After=dev-%i.device

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/local/bin/automount %I
ExecStop=/usr/bin/pumount /dev/%I

Step 4 – Create Mount Script

sudo vi /usr/local/bin/automount

#!/bin/bash

PART=$1
FS_LABEL=`lsblk -o name,label | grep ${PART} | awk '{print $2}'`

if [ -z ${FS_LABEL} ]
then
    /usr/bin/pmount --umask 000 --noatime -w --sync /dev/${PART} /media/${PART}
else
    /usr/bin/pmount --umask 000 --noatime -w --sync /dev/${PART} /media/${FS_LABEL}_${PART}
fi

sudo chmod +x /usr/local/bin/automount

Step 5 – Should be working, but if not…

You’ll see your USB drives mounted under /media

Per the comment from James:

And rather than reboot, UDEV should automatically detect new rules[2], but if it fails to:

udevadm control –reload

If that doesn’t work… you can always try turning it off and on again 🙂

References

• pmount
• Stack Exchange Post