diff --git a/run/disk.sh b/run/disk.sh
index 90865a2..3f1b41e 100644
--- a/run/disk.sh
+++ b/run/disk.sh
@@ -163,6 +163,10 @@ if [ -f "${DATA2}" ]; then
     -drive file=${DATA2},if=none,id=drive-userdata2,format=raw,cache=${DISK_CACHE},aio=${DISK_IO},discard=${DISK_DISCARD},detect-zeroes=on \
     -device scsi-hd,bus=hw-userdata2.0,channel=0,scsi-id=0,lun=0,drive=drive-userdata2,id=userdata2,rotation_rate=${DISK_ROTATION},bootindex=4"
 
+else
+
+  [ -d "/storage2" ] && error "Disk image ${DATA2} does not exist! Use an empty file of at least 6 GB." && exit 53
+
 fi
 
 DATA3="/storage3/data.img"
@@ -174,11 +178,17 @@ if [ -f "${DATA3}" ]; then
     -drive file=${DATA3},if=none,id=drive-userdata3,format=raw,cache=${DISK_CACHE},aio=${DISK_IO},discard=${DISK_DISCARD},detect-zeroes=on \
     -device scsi-hd,bus=hw-userdata3.0,channel=0,scsi-id=0,lun=0,drive=drive-userdata3,id=userdata3,rotation_rate=${DISK_ROTATION},bootindex=5"
 
+else
+
+  [ -d "/storage3" ] && error "Disk image ${DATA3} does not exist! Use an empty file of at least 6 GB." && exit 54
+
 fi
 
-DEVICE="/device"
+: ${DEVICE:=''}        # Docker variable to passthrough a block device, like /dev/vdc1.
 
-if [ -d "${DEVICE}" ]; then
+if [ -n "${DEVICE}" ]; then
+
+  [ ! -b "${DEVICE}" ] && error "Device ${DEVICE} cannot be found! Please add it to the 'devices' section of your compose file." && exit 55
 
   DISK_OPTS="${DISK_OPTS} \
     -device virtio-scsi-pci,id=hw-userdata4,bus=pcie.0,addr=0xf \