Tool used to create Debian and Raspberry Pi derived OS images.
Dependencies
pi-gen runs on Debian-based operating systems. Currently it is only
supported on either Debian Buster or Debian Bullseye and is known to
have issues building on earlier releases of these systems. On other
Linux distributions it may be possible to use the Docker build described
below.
To install the required dependencies for pi-gen you
should run:
The file depends contains a list of tools needed. The
format of this package is
<tool>[:<debian-package>].
Notes
Implementation uses qcow2
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.
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
Config
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:
IMG_NAMErequired (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.
INSTALL_RECOMMENDS (Default: unset)
If set to one, i.e. INSTALL_RECOMMENDS=1, installation
process will install recommended packages. Otherwise (default):
apt selection without recommended and suggested
Note: apt cache is disabled for all target
configurations.
ROOTFS_RO (Default: unset)
If set to one, i.e. ROOTFS_RO=1, the root filesystem
will be set read-only, an initramfs is used to load it via
loopfs and a tmpfs created at boot containing
the overlayfs mutable storage for
/etc
/home
/var
/srv
Further all apt-daily systemd tasks are disabled, the
ssh host keys are retained while regenerate_ssh_host_keys
is disabled and the final /boot/config.txt has
splash disabled (no rainbow).
REDUCED_FOOTPRINT (Default: unset)
If set to one, i.e. REDUCED_FOOTPRINT=1, installation
will attempt to keep the footprint as small as possible. This is
intended for small devices, perhaps in addition to
ROOTFS_RO=1. The following efforts are made:
apt selection without recommended and suggested
Reduced
Disk Footprint (Ubuntu) for most /usr/share/doc and
most locales but [ en*, da*,
de*, es*, fi*, fr*,
is*, nb*, ru*, sv*,
zh* ], i.e. includes locale for
English en
Danish da
German de
Icelandic is
Spanish es
Finnish fi
French fr
Norwegian Bokmål nb
Russia nb
Swedish sv
Chinese zh
It is also recommended to not include
stage3bstage4 and stage5 for a small
embedded system, as they contain heavy window-manager and broader
desktop applications, etc.
See detailed notes on stages below.
Note: apt cache is disabled for all target
configurations.
BASE_QCOW2_SIZE (Default: 15200M)
Size of the virtual qcow2 disk given in multiples of 1024, i.e. KiB,
MiB or GiB. 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.
The release version to build images against. Valid values are jessie,
stretch, buster and bullseye
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_ZIP (Default: 1)
Setting to 0 will deploy the actual image
(.img) instead of a zipped image
(.zip).
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
FIRST_USER_PASS (Default: "raspberry")
Password for the first user
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.
Docker Build
Docker can be used to perform the build inside a container. This
partially isolates the build from the host system, and allows using the
script on non-debian based systems (e.g. Fedora Linux). The isolate is
not complete due to the need to use some kernel level services for arm
emulation (binfmt) and loop devices (losetup).
To build:
vi config # Edit your config file. See above../build-docker.sh
If everything goes well, your finished image will be in the
deploy/ folder. You can then remove the build container
with docker rm -v pigen_work
If something breaks along the line, you can edit the corresponding
scripts, and continue:
CONTINUE=1 ./build-docker.sh
To examine the container after a failure you can enter a shell within
it using:
sudo docker run -it--privileged--volumes-from=pigen_work pi-gen /bin/bash
After successful build, the build container is by default removed.
This may be undesired when making incremental changes to a customized
build. To prevent the build script from remove the container add
PRESERVE_CONTAINER=1 ./build-docker.sh
There is a possibility that even when running from a docker
container, the installation of qemu-user-static will
silently fail when building the image because
binfmt-supportmust be enabled on the underlying
kernel. An easy fix is to ensure binfmt-support is
installed on the host machine before starting the
./build-docker.sh script (or using your own docker build
solution).
Passing arguments to Docker
When the docker image is run various required command line arguments
are provided. For example the system mounts the /dev
directory to the /dev directory within the docker
container. If other arguments are required they may be specified in the
PIGEN_DOCKER_OPTS environment variable. For example setting
PIGEN_DOCKER_OPTS="--add-host foo:192.168.0.23" will add
'192.168.0.23 foo' to the /etc/hosts file in the container.
The --name and --privileged options are
already set by the script and should not be redefined.
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.
stage0 - 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.
stage1 - 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.
stage2 - 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.
Python and Lua are included here, as they are often required by
certain setup scripts.
stage3a - litex system. Contains a minimal
xserver-xorg subset and dwm with stterm,
suitable for embedded systems using graphics.
stage3a_dev - litexdev system. Contains full
commandline development tools and developer library packages based on
stage3a inclusive build-essential, gcc, clang, OpenJDK
11, etc.
stage3b - desktop system. Contains a complete
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.
stage4 - 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.
stage5 - 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 systemecho"IMG_NAME='Raspbian'"> configtouch ./stage3/SKIP ./stage4/SKIP ./stage5/SKIPtouch ./stage4/SKIP_IMAGES ./stage5/SKIP_IMAGESsudo ./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
Regarding Qcow2 image
building
Get infos about the image in
use
If you issue the two commands shown in the example below in a second
command shell while a build is running you can find out, which network
block device is currently being used and which qcow2 image is bound to
it.
Here you can see, that the qcow2 image
image-stage4.qcow2 is currently connected to
/dev/nbd1 with the associated partition map
/dev/mapper/nbd1p1. Don't worry that lsblk
shows two entries. It is totally fine, because the device map is
accessible via /dev/mapper/nbd1p1 and also via
/dev/dm-0. This is all part of the device mapper
functionality of the kernel. See dmsetup for further
information.
Mount a qcow2 image
If you want to examine the content of a a single stage, you can
simply mount the qcow2 image found in the WORK_DIR
directory with the tool ./imagetool.sh.
See ./imagetool.sh -h for further details on how to use
it.
Disconnect an image
if something went wrong
It can happen, that your build stops in case of an error. Normally
./build.sh should handle image disconnection appropriately,
but in rare cases, especially during a Docker build, this may not work
as expected. If that happens, starting a new build will fail and you may
have to disconnect the image and/or device yourself.
A typical message indicating that there are some orphaned device
mapper entries is this:
Failed to set NBD socket
Disconnect client, due to: Unexpected end-of-file before all bytes were read
If that happens go through the following steps:
First, check if the image is somehow mounted to a directory entry
and umount it as you would any other block device, like i.e. a hard disk
or USB stick.
Second, to disconnect an image from qemu-nbd, the
QEMU Disk Network Block Device Server, issue the following command (be
sure to change the device name to the one actually used):
sudo qemu-nbd -d /dev/nbd1
Note: if you use Docker build, normally no active
qemu-nbd process exists anymore as it will be terminated
when the Docker container stops.
To disconnect a device partition map from the network block
device, execute:
Note: The imagetool.sh command will cleanup any
/dev/nbdX that is not connected to a running qemu-nbd
daemon. Be careful if you use network block devices for other tasks
utilizing NBDs on your build machine as well.
Now you should be able to start a new build without running into
troubles again. Most of the time, especially when using Docker build,
you will only need no. 3 to get everything up and running again.
Linux is able execute binaries from other architectures, meaning that
it should be possible to make use of pi-gen on an x86_64
system, even though it will be running ARM binaries. This requires
support from the binfmt_misc
kernel module.
You may see the following error:
update-binfmts: warning: Couldn't load the binfmt_misc module.
To resolve this, ensure that the following files are available
(install them if necessary):
