Add script to create an .img to be flashed to raspberry pi

Author: MattBlack85

scripts/build_img.sh

@@ -0,0 +1,105 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# --- settings ---
+IMG=${IMG:-archarm-rpi-aarch64.img}
+SIZE=${SIZE:-4G}          # total image size
+BOOT_MB=${BOOT_MB:-768}   # FAT32 /boot size in MiB
+ROOT_LABEL=${ROOT_LABEL:-ALARM_ROOT}
+BOOT_LABEL=${BOOT_LABEL:-ALARM_BOOT}
+ROOTFS_TAR=${ROOTFS_TAR:-rootfs.tar}
+
+# sanity
+[ -f "$ROOTFS_TAR" ] || { echo "Missing $ROOTFS_TAR"; exit 1; }
+
+# tools needed: sfdisk, losetup, mkfs.vfat, mkfs.ext4, tar, rsync or cp -a
+command -v sfdisk >/dev/null
+command -v losetup >/dev/null
+
+# --- create sparse disk file ---
+truncate -s "$SIZE" "$IMG"
+
+# --- partition table: 1MiB align, 768MiB FAT32 boot, rest ext4 root ---
+BOOT_START=2048                               # 1MiB (512b sectors)
+BOOT_SIZE=$(( BOOT_MB * 2048 ))               # sectors (MiB * 2048)
+sfdisk "$IMG" <<EOF
+label: dos
+unit: sectors
+${IMG}1 : start=${BOOT_START}, size=${BOOT_SIZE}, type=c
+${IMG}2 : start=$((BOOT_START+BOOT_SIZE)), type=83
+EOF
+
+# --- map loop with partitions ---
+LOOP=$(sudo losetup --find --show --partscan "$IMG")
+BOOT_DEV=${LOOP}p1
+ROOT_DEV=${LOOP}p2
+PARTUUID=$(sudo blkid -s PARTUUID -o value "$ROOT_DEV")
+
+# --- mkfs ---
+sudo mkfs.vfat -F 32 -n "$BOOT_LABEL" "$BOOT_DEV"
+sudo mkfs.ext4 -F -L "$ROOT_LABEL" "$ROOT_DEV"
+
+BOOT_UUID=$(sudo blkid -s UUID -o value "$BOOT_DEV")
+ROOT_UUID=$(sudo blkid -s UUID -o value "$ROOT_DEV")
+echo "BOOT UUID is $BOOT_UUID"
+echo "ROOT UUID is $ROOT_UUID"
+
+# --- mount ---
+sudo mkdir -p /mnt/arch-root /mnt/arch-boot
+sudo mount "$ROOT_DEV" /mnt/arch-root
+sudo mkdir -p /mnt/arch-root/boot
+sudo mount "$BOOT_DEV" /mnt/arch-boot
+
+# --- extract rootfs (preserve xattrs/owners) ---
+sudo tar --numeric-owner -xpf "$ROOTFS_TAR" -C /mnt/arch-root
+
+# --- move/copy boot files to the FAT32 partition ---
+# Official instructions literally "move root/boot/* to boot" when using their tarball.
+# We do the equivalent from our extracted rootfs.
+if [ -d /mnt/arch-root/boot ] && [ -n "$(ls -A /mnt/arch-root/boot)" ]; then
+  sudo cp -a /mnt/arch-root/boot/* /mnt/arch-boot/
+fi
+
+# --- minimal boot config depending on strategy ---
+# If you installed linux-rpi (+ raspberrypi-bootloader), firmware boots kernel*.img via config.txt/cmdline.txt
+if [ -f /mnt/arch-boot/kernel8.img ]; then
+  printf 'arm_64bit=1\nenable_uart=1\n' | sudo tee /mnt/arch-boot/config.txt >/dev/null
+  # root= by PARTUUID (safest). Discover it:
+  sudo tee /mnt/arch-boot/cmdline.txt >/dev/null <<EOF
+console=serial0,115200 console=ttyAMA0,115200 root=PARTUUID=${PARTUUID} rw rootwait
+EOF
+fi
+
+# If you installed linux-aarch64 + uboot-raspberrypi, ensure extlinux.conf exists
+if [ -d /mnt/arch-boot/extlinux ]; then
+  :
+elif [ -f /mnt/arch-boot/u-boot.bin ] || [ -f /mnt/arch-root/boot/u-boot.bin ]; then
+  sudo install -d /mnt/arch-boot/extlinux
+  sudo tee /mnt/arch-boot/extlinux/extlinux.conf >/dev/null <<EOF
+DEFAULT arch
+MENU TITLE Arch Linux ARM
+TIMEOUT 3
+
+LABEL arch
+  LINUX /Image
+  INITRD /initramfs-linux.img
+  FDTDIR /dtbs
+  APPEND root=PARTUUID=${PARTUUID} rw rootwait console=ttyAMA0,115200 console=serial0,115200
+EOF
+fi
+
+# --- fstab (Pi 4 aarch64 note: ALARM docs use mmcblk1) ---
+# Use PARTUUIDs so device names don’t matter.
+sudo tee /mnt/arch-root/etc/fstab <<EOF
+UUID=${ROOT_UUID}  /      ext4   defaults,noatime  0 1
+UUID=${BOOT_UUID}  /boot  vfat   defaults,noatime  0 2
+EOF
+
+sync
+
+# --- unmount & detach ---
+sudo umount /mnt/arch-boot || true
+sudo umount /mnt/arch-root || true
+sudo losetup -d "$LOOP"
+
+echo "OK: ${IMG} is ready."