Can dope an .img file directly

.gitignore

@@ -1,2 +1,3 @@
 /build/
 parameters.env
+*.img

README.md

@@ -4,6 +4,8 @@ This project aims to create an easy way to burn a RPi SD card with an [Ubuntu Se
 
 ## Quick Start
 
+### Configure Torch and SSH Parameters
+
 Place your settings in `parameters.env`
 
 ```bash
@@ -22,6 +24,9 @@ EOF
 * SSH_PUBKEY - Pubkey to copy to the ~/.ssh directory for SSH access
 * TORCH_CONFIG_DIR - Directory containing Torch [configuration](/bj/torch-agent) files
 
+
+### Manual Image Configuration
+
 Run `build.sh`
 
 ```bash
@@ -33,3 +38,12 @@ Find the built configuration bundle in the `build` directory and extract it to t
 ```bash
 tar -xzvf build/rpi-cloud-init.tgz /mnt/rpi-boot/
 ```
+
+### Automatic Image Configuration
+
+Place a decompressed Ubuntu Server `*.img` file in the project directory and
+use `img-config.sh` to build and dope the boot partition of `*.img` file directly
+
+```bash
+sudo ./img-config.sh ubuntu-20.04.1-preinstalled-server-arm64+raspi.img
+```

img-config.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+SECTOR_BYTES=512
+SECTOR_START=2048
+OFFSET=$(($SECTOR_BYTES*$SECTOR_START))
+
+./build.sh
+mkdir -p boot-part
+mount -o rw,loop,offset=$OFFSET $1 ./boot-part
+tar -xzvf build/rpi-cloud-init.tgz -C boot-part
+umount ./boot-part
+rmdir ./boot-part