diff --git a/install-stage1.sh b/install-stage1.sh
index 4978dc0..b7af702 100644
--- a/install-stage1.sh
+++ b/install-stage1.sh
@@ -102,6 +102,27 @@ else
   exit 1
 fi
 
+if grep "$TARGET_DISK" /proc/mounts >> $LOGFILE 2>&1; then
+  echo "The device seems to be mounted. Unmount?"
+  if yesno; then
+    echo -n "Attempting to unmount... "
+    readarray -t MOUNTPOINTS <<< "$(findmnt --raw --noheadings --output SOURCE,TARGET | grep "$TARGET_DISK" | sed 's/^[^ ]* //')"
+    for I in ${!MOUNTPOINTS[@]}; do
+      umount -R "${MOUNTPOINTS[$I]}" >> $LOGFILE 2>&1
+    done
+    if grep "$TARGET_DISK" /proc/mounts >> $LOGFILE 2>&1; then
+      echo "failed"
+      echo "It seems the device is still mounted. Installation cannot continue."
+      exit 1
+    else
+      echo "done"
+    fi
+  else
+    echo "Aborting."
+    exit 1
+  fi
+fi
+
 echo -n "Wiping and partitioning storage... "
 # new GPT
 # 2M BIOS GRUB