Setup external hard drive

You should choose an external hard drive that will spin down automatically after idle(no I/O activity) for some time. And in order to let it idle, you need to dismount the drive; that leads to the use of autofs.

Add this to /etc/auto.master:

# dismount after no file access for 120 seconds:
/mnt /etc/auto.mnt --timeout=120

Create file etc/auto.mnt with this:

usbhd -fstype=ext3,rw :/dev/disk/by-label/USB40G

Add thsi line to /etc/nsswitch.conf:

automount:     files

Restart autofs to take effect.

After that, whenever you access /mnt/usbhd, the partition labeled USB40G will be auto mounted.

First, don't use autofs for the drive.

tune2fs -L "USB1TB" /dev/sda1

/dev/disk/by-label/USB1TB /mnt/usbhd ext3 defaults,noauto,relatime,data=ordered 0 0

Add these line to /etc/udev/rules.d/mount-usb.rules:

ENV{ID_FS_LABEL}=="USB1TB", ACTION=="add", RUN+="/usr/local/bin/usbhd_added.sh"
ENV{ID_FS_LABEL}=="USB1TB", ACTION=="remove", RUN+="/bin/umount /mnt/usbhd", RUN+="/bin/touch /var/tmp/usbhd_removed"

Create file /usr/local/bin/usbhd_added.sh:

cat > /usr/local/bin/usbhd_added.sh <<EOT
#!/bin/sh

/bin/mount /mnt/usbhd

# restart services that broke after usbhd removed and inserted again
if [ -f /var/tmp/usbhd_removed ] ; then

        /bin/rm -f /var/tmp/usbhd_removed

        /usr/sbin/service minidlna restart
        
        # more services here
fi
EOT

chmod 755 /usr/local/bin/usbhd_added.sh

So, whenever the drive is plugged, it is mounted automatically, and dependent services are restarted as needed.