Fix SSH choice and image build safeguards

pi4/build/README.md

@@ -29,9 +29,10 @@ The script is designed for an x86_64 Arch host so it can emulate ARM binaries wi
 
 ## Building Your First Image
 1. Become root (`sudo -i`) so the script can create loop devices and mount them.
-2. From `/path/to/stormux`, run:
+2. From the Pi builder directory, run:
    ```bash
-   sudo ./pi4/build/build-stormux.sh -l en_US -s 8
+   cd /path/to/stormux/pi4/build
+   sudo ./build-stormux.sh -l en_US -s 8
    ```
    - The builder creates an aarch64 image for Raspberry Pi 4/5-class systems.
    - `-l en_US` selects the locale (use `es_ES`, `fr_FR`, etc.).

pi4/build/build-stormux.sh

@@ -236,6 +236,38 @@ if [ "$(whoami)" != "root" ] ; then
     exit 1
 fi
 
+# Refuse to mount the image over an unrelated filesystem already using /mnt.
+if ! command -v mountpoint > /dev/null 2>&1; then
+    echo "Error: mountpoint is required to verify that /mnt is available."
+    exit 1
+fi
+
+if [[ ! -d /mnt || ! -w /mnt ]]; then
+    echo "Error: /mnt is missing or not writable. Please create or fix permissions."
+    exit 1
+fi
+
+if mountpoint -q /mnt; then
+    if [[ -t 0 ]]; then
+        read -rp "/mnt is already mounted. Unmount it to continue? [y/N] " answerText
+        case "$answerText" in
+            y|Y|yes|YES)
+                if ! umount /mnt; then
+                    echo "Error: Failed to unmount /mnt."
+                    exit 1
+                fi
+                ;;
+            *)
+                echo "Error: Refusing to proceed while /mnt is mounted."
+                exit 1
+                ;;
+        esac
+    else
+        echo "Error: /mnt is already mounted. Refusing to proceed in non-interactive mode."
+        exit 1
+    fi
+fi
+
 # make sure the needed tools are installed
 if [[ "$(uname -m)" == "x86_64" ]]; then
     if ! pacman -Q qemu-user-static &> /dev/null ; then