Image script: trixie arm64, NetworkManager wifi, any free loop device

- Download the 2026-09-15 Raspberry Pi OS trixie arm64 lite image.
- Trixie (and NetworkManager-based bookworm) ignore wpa_supplicant.conf on the boot
  partition: write a NetworkManager profile there instead, and set the regulatory
  domain on the kernel command line. The SSID is now asked for too.
- Use whichever loop device is free rather than a hard-coded /dev/loop42, mount into a
  temporary directory, and unmount and detach on any exit. Resolve paths from the
  script's own location, and refuse to overwrite an already customised image.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/create-raspian-image/create-raspian-image.sh

@@ -2,10 +2,12 @@
 
 set -e  # exit on error
 
-TARGET_FOLDER="./rpi_image"
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
-IMG_FILE_BASENAME="2023-12-11-raspios-bookworm-armhf-lite"
+TARGET_FOLDER="$SCRIPT_DIR/rpi_image"
-#DOWNLOAD_URL="https://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2021-11-08/${IMG_FILE_BASENAME}.zip"
+#IMG_FILE_BASENAME="2023-12-11-raspios-bookworm-armhf-lite"
-DOWNLOAD_URL="https://downloads.raspberrypi.com/raspios_lite_armhf/images/raspios_lite_armhf-2023-12-11/${IMG_FILE_BASENAME}.img.xz"
+#DOWNLOAD_URL="https://downloads.raspberrypi.com/raspios_lite_armhf/images/raspios_lite_armhf-2023-12-11/${IMG_FILE_BASENAME}.img.xz"
+IMG_FILE_BASENAME="2026-09-15-raspios-trixie-arm64-lite"
+DOWNLOAD_URL="https://downloads.raspberrypi.com/raspios_lite_arm64/images/raspios_lite_arm64-2026-09-15/${IMG_FILE_BASENAME}.img.xz"
 
 echo "This script downloads raspian lite, and modifies the image to  enable SSH and set hostname"
 
@@ -14,15 +16,20 @@ if [[ $EUID -ne 0 ]]; then
    exit 1
 fi
 
-echo -n Hostname of new pi
 read -p "Hostname of new pi [newrpi]: " RPI_HOSTNAME
+read -p "WIFI SSID (only used if a password is given) [WLAN]: " WIFI_SSID
 read -p "WIFI password (leave empty for non-wifi setup) [] " WIFI_PASSWORD
 RPI_HOSTNAME=${RPI_HOSTNAME:-newrpi}
+WIFI_SSID=${WIFI_SSID:-WLAN}
 
-SCRIPT_DIR=`pwd`
+mkdir -p "$TARGET_FOLDER"
-mkdir -p $TARGET_FOLDER
+cd "$TARGET_FOLDER"
-cd $TARGET_FOLDER
 
+if [ -e "${IMG_FILE_BASENAME}.img" ]; then
+   echo "${TARGET_FOLDER}/${IMG_FILE_BASENAME}.img already exists (already customised?)."
+   echo "Remove it first if you want to start over."
+   exit 1
+fi
 
 echo "Downloading image"
 wget ${DOWNLOAD_URL}
@@ -36,36 +43,74 @@ unxz ${IMG_FILE_BASENAME}.img.xz
 
 
 echo "Mounting image"
-mkdir mounted_image
+MOUNT_DIR=$(mktemp -d "$TARGET_FOLDER/mounted_image.XXXXXX")
-mkdir mounted_image/boot
+LOOP_DEV=""
-mkdir mounted_image/system
+cleanup() {
-losetup -P /dev/loop42 ${IMG_FILE_BASENAME}.img
+   set +e
-mount /dev/loop42p1 mounted_image/boot
+   umount "$MOUNT_DIR/boot" "$MOUNT_DIR/system" 2>/dev/null
-mount /dev/loop42p2 mounted_image/system
+   [ -n "$LOOP_DEV" ] && losetup -d "$LOOP_DEV"
+   rmdir "$MOUNT_DIR/boot" "$MOUNT_DIR/system" "$MOUNT_DIR" 2>/dev/null
+}
+trap cleanup EXIT
+
+mkdir "$MOUNT_DIR/boot" "$MOUNT_DIR/system"
+LOOP_DEV=$(losetup -f --show -P ${IMG_FILE_BASENAME}.img)
+mount ${LOOP_DEV}p1 "$MOUNT_DIR/boot"    # firmware partition, /boot/firmware on the Pi
+mount ${LOOP_DEV}p2 "$MOUNT_DIR/system"
 
 
 echo "Enabling SSH and writing hostname"
-echo $RPI_HOSTNAME > mounted_image/system/etc/hostname
+echo $RPI_HOSTNAME > "$MOUNT_DIR/system/etc/hostname"
-touch mounted_image/boot/ssh  # startup ssh
+touch "$MOUNT_DIR/boot/ssh"  # startup ssh
-sed -i "/^#PermitRootLogin/ cPermitRootLogin prohibit-password" mounted_image/system/etc/ssh/sshd_config
+sed -i "/^#PermitRootLogin/ cPermitRootLogin prohibit-password" "$MOUNT_DIR/system/etc/ssh/sshd_config"
-mkdir -p mounted_image/system/root/.ssh
+mkdir -p "$MOUNT_DIR/system/root/.ssh"
-cat $SCRIPT_DIR/*.pub > mounted_image/system/root/.ssh/authorized_keys
+cat $SCRIPT_DIR/*.pub > "$MOUNT_DIR/system/root/.ssh/authorized_keys"
-chmod 700 mounted_image/system/root/.ssh
+chmod 700 "$MOUNT_DIR/system/root/.ssh"
-chmod 600 mounted_image/system/root/.ssh/authorized_keys
+chmod 600 "$MOUNT_DIR/system/root/.ssh/authorized_keys"
 
 
 if [ -z "$WIFI_PASSWORD" ]
 then
    echo "Skipping WIFI setup"
+elif [ -d "$MOUNT_DIR/system/etc/NetworkManager" ] && [ -e "$MOUNT_DIR/boot/user-data" ]
+then
+   # Trixie (and bookworm images from 2023-10 on, when they use NetworkManager) ignore
+   # wpa_supplicant.conf on the boot partition; give NetworkManager a connection profile.
+   echo "Setting up initial wifi config (NetworkManager)"
+   NM_DIR="$MOUNT_DIR/system/etc/NetworkManager/system-connections"
+   mkdir -p "$NM_DIR"
+   /bin/cat <<EOM >"$NM_DIR/wifi.nmconnection"
+[connection]
+id=wifi
+type=wifi
+autoconnect=true
+
+[wifi]
+mode=infrastructure
+ssid=${WIFI_SSID}
+
+[wifi-security]
+key-mgmt=wpa-psk
+psk=${WIFI_PASSWORD}
+
+[ipv4]
+method=auto
+
+[ipv6]
+method=auto
+EOM
+   chmod 600 "$NM_DIR/wifi.nmconnection"  # NetworkManager ignores profiles readable by others
+   # regulatory domain, so the 5GHz channels and the right power limits are usable at boot
+   sed -i '1 s/$/ cfg80211.ieee80211_regdom=DE/' "$MOUNT_DIR/boot/cmdline.txt"
 else
-   echo "Setting up initial wifi config"
+   echo "Setting up initial wifi config (wpa_supplicant)"
-   /bin/cat <<EOM >mounted_image/boot/wpa_supplicant.conf
+   /bin/cat <<EOM >"$MOUNT_DIR/boot/wpa_supplicant.conf"
 country=DE
 ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
 update_config=1
 
 network={
-   ssid="WLAN"
+   ssid="${WIFI_SSID}"
    psk="${WIFI_PASSWORD}"
 }
 EOM
@@ -75,12 +120,8 @@ fi
 
 echo "Unmounting image and other cleanup"
 sleep 3 # to prevent "device is busy"
-umount /dev/loop42p1
+cleanup
-umount /dev/loop42p2
+trap - EXIT
-losetup -d /dev/loop42
-rmdir mounted_image/boot
-rmdir mounted_image/system
-rmdir mounted_image
 rm ${IMG_FILE_BASENAME}.img.xz.sha256
 chmod a+rw ${IMG_FILE_BASENAME}.img .