MirrorOS

Tool used to create MirrorOS images, pre-compipled with image processing. Forked from pi-gen.

Dependencies

The tool should be run in Debian systems, and pre-installed with these packages:

sudo apt-get install coreutils quilt parted qemu-user-static debootstrap zerofree zip \
dosfstools libarchive-tools libcap2-bin grep rsync xz-utils file git curl bc \
qemu-utils kpartx gpg pigz

The file depends contains a list of tools needed. The format of this package is <tool>[:<debian-package>].

Getting started with building your images

There are 2 ways to build the image:

1. Build manually

The image can be build by cloning the repo and run file build.sh as following:

git clone https://github.com/MasterPi-2124/MirrorOS
cd MirrorOS
sudo bash build.sh -c config

with config is the config file with parameters in detail below. The image will be stored in deploy/ by default. You can change the directory in config file.

2. Github Actions

There also an action of building the image. Go to Actions tab and download the artifact.

Config file

Upon execution, build.sh will source the file config in the current working directory. This bash shell fragment is intended to set needed environment variables.

The following environment variables are supported:

• GIT_USERNAME (Default: unset)

  The default username for git. Useful for code nerds.

• GIT_EMAIL (Default: unset)

The default email for git. Useful for code nerds as above.

• IMG_NAME required (Default: unset)

  The name of the image to build with the current stage directories. Setting IMG_NAME=Raspbian is logical for an unmodified RPi-Distro/pi-gen build, but you should use something else for a customized version. Export files in stages may add suffixes to IMG_NAME.

• USE_QCOW2 EXPERIMENTAL (Default: 0 )

  Instead of using traditional way of building the rootfs of every stage in single subdirectories and copying over the previous one to the next one, qcow2 based virtual disks with backing images are used in every stage. This speeds up the build process and reduces overall space consumption significantly.

  Additional optional parameters regarding qcow2 build:

  • BASE_QCOW2_SIZE (Default: 12G)

    Size of the virtual qcow2 disk. Note: it will not actually use that much of space at once but defines the maximum size of the virtual disk. If you change the build process by adding a lot of bigger packages or additional build stages, it can be necessary to increase the value because the virtual disk can run out of space like a normal hard drive would.

  CAUTION: Although the qcow2 build mechanism will run fine inside Docker, it can happen that the network block device is not disconnected correctly after the Docker process has ended abnormally. In that case see Disconnect an image if something went wrong

• RELEASE (Default: bullseye)

  The release version to build images against. Valid values are jessie, stretch, buster, bullseye, and testing.

• APT_PROXY (Default: unset)

  If you require the use of an apt proxy, set it here. This proxy setting will not be included in the image, making it safe to use an apt-cacher or similar package for development.

  If you have Docker installed, you can set up a local apt caching proxy to like speed up subsequent builds like this:

  docker-compose up -d
  echo 'APT_PROXY=http://172.17.0.1:3142' >> config
  

• BASE_DIR (Default: location of build.sh)

  CAUTION: Currently, changing this value will probably break build.sh

  Top-level directory for pi-gen. Contains stage directories, build scripts, and by default both work and deployment directories.

• WORK_DIR (Default: "$BASE_DIR/work")

  Directory in which pi-gen builds the target system. This value can be changed if you have a suitably large, fast storage location for stages to be built and cached. Note, WORK_DIR stores a complete copy of the target system for each build stage, amounting to tens of gigabytes in the case of Raspbian.

  CAUTION: If your working directory is on an NTFS partition you probably won't be able to build: make sure this is a proper Linux filesystem.

• DEPLOY_DIR (Default: "$BASE_DIR/deploy")

  Output directory for target system images and NOOBS bundles.

• DEPLOY_COMPRESSION (Default: zip)

  Set to:

  • none to deploy the actual image (.img).
  • zip to deploy a zipped image (.zip).
  • gz to deploy a gzipped image (.img.gz).
  • xz to deploy a xzipped image (.img.xz).

• DEPLOY_ZIP (Deprecated)

  This option has been deprecated in favor of DEPLOY_COMPRESSION.

  If DEPLOY_ZIP=0 is still present in your config file, the behavior is the same as with DEPLOY_COMPRESSION=none.

• COMPRESSION_LEVEL (Default: 6)

  Compression level to be used when using zip, gz or xz for DEPLOY_COMPRESSION. From 0 to 9 (refer to the tool man page for more information on this. Usually 0 is no compression but very fast, up to 9 with the best compression but very slow ).

• USE_QEMU (Default: "0")

  Setting to '1' enables the QEMU mode - creating an image that can be mounted via QEMU for an emulated environment. These images include "-qemu" in the image file name.

• LOCALE_DEFAULT (Default: "en_GB.UTF-8" )

  Default system locale.

• TARGET_HOSTNAME (Default: "raspberrypi" )

  Setting the hostname to the specified value.

• KEYBOARD_KEYMAP (Default: "gb" )

  Default keyboard keymap.

  To get the current value from a running system, run debconf-show keyboard-configuration and look at the keyboard-configuration/xkb-keymap value.

• KEYBOARD_LAYOUT (Default: "English (UK)" )

  Default keyboard layout.

  To get the current value from a running system, run debconf-show keyboard-configuration and look at the keyboard-configuration/variant value.

• TIMEZONE_DEFAULT (Default: "Europe/London" )

  Default keyboard layout.

  To get the current value from a running system, look in /etc/timezone.

• FIRST_USER_NAME (Default: pi)

  Username for the first user. This user only exists during the image creation process. Unless DISABLE_FIRST_BOOT_USER_RENAME is set to 1, this user will be renamed on the first boot with a name chosen by the final user. This security feature is designed to prevent shipping images with a default username and help prevent malicious actors from taking over your devices.

• FIRST_USER_PASS (Default: unset)

  Password for the first user. If unset, the account is locked.

• DISABLE_FIRST_BOOT_USER_RENAME (Default: 0)

  Disable the renaming of the first user during the first boot. This make it so FIRST_USER_NAME stays activated. FIRST_USER_PASS must be set for this to work. Please be aware of the implied security risk of defining a default username and password for your devices.

• WPA_ESSID, WPA_PASSWORD and WPA_COUNTRY (Default: unset)

  If these are set, they are use to configure wpa_supplicant.conf, so that the Raspberry Pi can automatically connect to a wireless network on first boot. If WPA_ESSID is set and WPA_PASSWORD is unset an unprotected wireless network will be configured. If set, WPA_PASSWORD must be between 8 and 63 characters.

• ENABLE_SSH (Default: 0)

  Setting to 1 will enable ssh server for remote log in. Note that if you are using a common password such as the defaults there is a high risk of attackers taking over you Raspberry Pi.

• PUBKEY_SSH_FIRST_USER (Default: unset)

Setting this to a value will make that value the contents of the FIRST_USER_NAME's ~/.ssh/authorized_keys. Obviously the value should therefore be a valid authorized_keys file. Note that this does not automatically enable SSH.

• PUBKEY_ONLY_SSH (Default: 0)

• Setting to 1 will disable password authentication for SSH and enable public key authentication. Note that if SSH is not enabled this will take effect when SSH becomes enabled.

• STAGE_LIST (Default: stage*)

  If set, then instead of working through the numeric stages in order, this list will be followed. For example setting to "stage0 stage1 mystage stage2" will run the contents of mystage before stage2. Note that quotes are needed around the list. An absolute or relative path can be given for stages outside the pi-gen directory.

A simple example for building Raspbian:

IMG_NAME='Raspbian'

The config file can also be specified on the command line as an argument the build.sh or build-docker.sh scripts.

./build.sh -c myconfig

This is parsed after config so can be used to override values set there.

How the build process works

The following process is followed to build images:

• Loop through all of the stage directories in alphanumeric order

• Move on to the next directory if this stage directory contains a file called "SKIP"

• Run the script prerun.sh which is generally just used to copy the build directory between stages.

• In each stage directory loop through each subdirectory and then run each of the install scripts it contains, again in alphanumeric order. These need to be named with a two digit padded number at the beginning. There are a number of different files and directories which can be used to control different parts of the build process:

  • 00-run.sh - A unix shell script. Needs to be made executable for it to run.

  • 00-run-chroot.sh - A unix shell script which will be run in the chroot of the image build directory. Needs to be made executable for it to run.

  • 00-debconf - Contents of this file are passed to debconf-set-selections to configure things like locale, etc.

  • 00-packages - A list of packages to install. Can have more than one, space separated, per line.

  • 00-packages-nr - As 00-packages, except these will be installed using the --no-install-recommends -y parameters to apt-get.

  • 00-patches - A directory containing patch files to be applied, using quilt. If a file named 'EDIT' is present in the directory, the build process will be interrupted with a bash session, allowing an opportunity to create/revise the patches.

• If the stage directory contains files called "EXPORT_NOOBS" or "EXPORT_IMAGE" then add this stage to a list of images to generate

• Generate the images for any stages that have specified them

It is recommended to examine build.sh for finer details.

Stage Anatomy

Raspbian Stage Overview

The build of Raspbian is divided up into several stages for logical clarity and modularity. This causes some initial complexity, but it simplifies maintenance and allows for more easy customization.

• Stage 0 - bootstrap. The primary purpose of this stage is to create a usable filesystem. This is accomplished largely through the use of debootstrap, which creates a minimal filesystem suitable for use as a base.tgz on Debian systems. This stage also configures apt settings and installs raspberrypi-bootloader which is missed by debootstrap. The minimal core is installed but not configured, and the system will not quite boot yet.

• Stage 1 - truly minimal system. This stage makes the system bootable by installing system files like /etc/fstab, configures the bootloader, makes the network operable, and installs packages like raspi-config. At this stage the system should boot to a local console from which you have the means to perform basic tasks needed to configure and install the system. This is as minimal as a system can possibly get, and its arguably not really usable yet in a traditional sense yet. Still, if you want minimal, this is minimal and the rest you could reasonably do yourself as sysadmin.

• Stage 2 - lite system. This stage produces the Raspbian-Lite image. It installs some optimized memory functions, sets timezone and charmap defaults, installs fake-hwclock and ntp, wireless LAN and bluetooth support, dphys-swapfile, and other basics for managing the hardware. It also creates necessary groups and gives the pi user access to sudo and the standard console hardware permission groups.

  There are a few tools that may not make a whole lot of sense here for development purposes on a minimal system such as basic Python and Lua packages as well as the build-essential package. They are lumped right in with more essential packages presently, though they need not be with pi-gen. These are understandable for Raspbian's target audience, but if you were looking for something between truly minimal and Raspbian-Lite, here's where you start trimming.

• Stage 3 - desktop system. Here's where you get the full desktop system with X11 and LXDE, web browsers, git for development, Raspbian custom UI enhancements, etc. This is a base desktop system, with some development tools installed.

• Stage 4 - Normal Raspbian image. System meant to fit on a 4GB card. This is the stage that installs most things that make Raspbian friendly to new users like system documentation.

• Stage 5 - The Raspbian Full image. More development tools, an email client, learning tools like Scratch, specialized packages like sonic-pi, office productivity, etc.

Stage specification

If you wish to build up to a specified stage (such as building up to stage 2 for a lite system), place an empty file named SKIP in each of the ./stage directories you wish not to include.

Then add an empty file named SKIP_IMAGES to ./stage4 and ./stage5 (if building up to stage 2) or to ./stage2 (if building a minimal system).

# Example for building a lite system
echo "IMG_NAME='Raspbian'" > config
touch ./stage3/SKIP ./stage4/SKIP ./stage5/SKIP
touch ./stage4/SKIP_IMAGES ./stage5/SKIP_IMAGES
sudo ./build.sh  # or ./build-docker.sh

If you wish to build further configurations upon (for example) the lite system, you can also delete the contents of ./stage3 and ./stage4 and replace with your own contents in the same format.

Skipping stages to speed up development

If you're working on a specific stage the recommended development process is as follows:

• Add a file called SKIP_IMAGES into the directories containing EXPORT_* files (currently stage2, stage4 and stage5)
• Add SKIP files to the stages you don't want to build. For example, if you're basing your image on the lite image you would add these to stages 3, 4 and 5.
• Run build.sh to build all stages
• Add SKIP files to the earlier successfully built stages
• Modify the last stage
• Rebuild just the last stage using sudo CLEAN=1 ./build.sh
• Once you're happy with the image you can remove the SKIP_IMAGES files and export your image to test