Update documentation

README.md

@@ -1,9 +1,56 @@
 # image-builder
-This repo contains script to build a `.iso` file to install customized Ubuntu.
+This repo contains script to build a `.iso` file to install customized Ubuntu for ICPC contests.
 
 # Usage
-Firstly, make a copy of `config.sh` called `local_config.sh` and change its content. You will want to change the `MIRROR` for faster installation.
 
-Then, run `./build.sh build` as `root`.
+## Prerequisites
 
-Install the `.iso` file on required machines, then head to `src/` for more information.
+> Note: The builder will require root access and may bind, use, and alternate two folders `/dev/` and `/run/`. If an error occurs during the run and the builder is not able to unmount the folders, it will be necessary to perform a physical hard reboot. Therefore, **it is recommended to run the builder in a virtual machine**.
+
+The builder requires a Linux system with at least 80GB of free storage and 4GB of RAM. The builder is tested on Ubuntu 20.04 LTS and 22.04 LTS.
+
+In case you want to build on a virtual machine, it is recommended to use VirtualBox, with **FIXED SIZE STORAGE** of at least 80GB and **4GB of RAM**.
+
+First, pull the repository and enter the directory:
+
+```bash
+git clone https://github.com/VNOI-Admin/image-builder.git
+cd image-builder
+```
+
+## Configuration
+
+After cloning the repository, you need to configure the builder. There are several files that need to be configured before building the image:
+
+- `config.local.sh`: A local copy of `config.sh` with personal configuration. This contains two important configuration variables:
+  - `ICPC_URL`: The URL to the ICPC ISO file. The ICPC Global may release new version of the ISO file that may overwrite the old one. Therefore, if errors related to failed download occur, please update this variable.
+  - `SUPER_PASSWD`: The password for the `root` user and bootloader.
+- `src/config.sh`: This a local copy of `src/config.sh` with machine-wide configuration. This contains several important configuration variables:
+  - `WEBSERVER_PUBLIC_ADDRESS`: The public address of the webserver, commonly for the backup server. This is accessible by the contestants without the need of VPN, therefore should only be used in case of VPN failure.
+  - `AUTH_ADDRESS`: The public address of the authentication and VPN central server.
+  - `SUBNET`: The subnet of the service nodes on the VPN network.
+- `src/config.local.sh`: This is an optional configuration file of `src/config.local.sh`. By setting the `VERSION` variable, it will store the version of the build to the image. Useful for debugging and tracking the version of the image.
+
+## Building
+
+To build the image for ICPC contests, run the following command:
+
+```bash
+sudo ./build.sh icpc_build
+```
+
+In case you want to use a specific version of the original ICPC ISO file, you can put the file inside the folder and rename it to `icpc-image.iso`. The builder will automatically use the file instead of downloading from the ICPC Global website.
+
+In case you want to forcefully download the original ICPC ISO file, you can run the following command:
+
+```bash
+sudo ./build.sh icpc_build --force
+```
+
+In case you want to optimize the build process, you can run the following command:
+
+```bash
+sudo ./build.sh icpc_build --github-action
+```
+
+This will automatically remove files that are not needed in the final stage of the build process. Should only be used in CI/CD environment or building on systems with limited storage, not for development.

build.sh

@@ -289,7 +289,7 @@ OPTIND=1 # Reset in case getopts has been used previously in the shell.
 help() {
     echo "Usage: $0 {icpc_build}"
     echo
-    echo "  icpc_build <image_file>: Build the ISO image based on the ICPC image"
+    echo "  icpc_build: Build the ISO image based on the ICPC image"
     echo "  generate_actions_secret: Generate actions secret from config.local.sh"
     echo "  clean: Clean up all files generated by this script"
     echo "  help: Show this help"

config.sh

@@ -1,11 +1,5 @@
 #!/bin/bash
 
-export ARCH="amd64" # Architecture
-export DISTRO="focal" # (DEPRECATED) Distribution, focal recommended
-export VARIANT="minbase" # Variant
-
-export MIRROR="http://vn.archive.ubuntu.com/ubuntu/" # see https://launchpad.net/ubuntu/+archivemirrors
-
 export INS_DIR="./live-build" # Installation directory
 export CHROOT=$INS_DIR/chroot
 export IMAGE=$INS_DIR/image