I found it hard to find info on the Pharo Bootstrap, so I went looking to understand the it by identifying very first creation on disk of the smallest�� "seed".image�� file that will later become the final build artifact.�� I'm sharing here to have a record I can refer to later, and maybe others find interesting.

Looking at the log from the latest build...

https://ci.inria.fr/pharo-ci-jenkins2/job/Test%20pending%20pull%20request%20and%20branch%20Pipeline/job/development/822/consoleFull

Searching on "BUILD_NUMBER=" indicates the first major CI step is...

+ BUILD_NUMBER=822 BOOTSTRAP_ARCH=32 bash ./bootstrap/scripts/2-download.sh�� [1]

which downloads 24MB " bootstrapImage.zip" [2]

which I presume is an almost full image to run the bootstrap process.

[1] https://github.com/pharo-project/pharo/blob/development/bootstrap/scripts/2-download.sh

[2] https://github.com/guillep/PharoBootstrap/releases/download/v1.4.1/bootstrapImage.zip

The next major CI step is...

+ BUILD_NUMBER=822 BOOTSTRAP_ARCH=32 bash ./bootstrap/scripts/3-prepare.sh�� [3]

which uses the downloaded "Pharo.image" to (I presume) produce the seed "bootstrap.image" file.��

(This is not indicated explicitly in the logs, but step 4 copies that file

with a shell command, so my presumption. It would be nice for this to be explicitly logged"

prepare.sh executes two commands...

./pharo Pharo.image ..../bootstrap/scripts/prepare_image.st --save --quit�� [4]

which seems to modify the downloaded "Pharo.image",��

not create bootstrap.image

./pharo Pharo.image ..../bootstrap/scripts/bootstrap.st --ARCH=32 --BUILD_NUMBER=822 --quit�� [5]

which does... "PBBootstrap fromCommandLine bootstrap"�� [6] [7]

which does...

�� PBBootstrap>>#bootstrap��

�� PBStepStartedSignal log: 'Starting�� Process.'.

�� self prepareBootstrap.

�� [self createImage ] on:AssertionFailure do: [ :e | e resume ].

�� self initializeImage.

�� PBStepFinishedSignal log: 'Process ended.'

and digging a bit...

�� PBBootstrap>>#createImage

�� | builder |

�� builder := PBImageBuilderSpur50 forArchitecture: architecture.

�� builder definitionFetcher: versionFetcher.

�� builder buildNumber: buildNumber.

�� builder imageFileReference: imageReference.

�� builder systemDefinition: ringEnvironment.

�� builder espellBackend instanceVariableMapping: (PBInstanceVariableMapping onEnvironment: ringEnvironment ).

�� builder bootstrap

�� PBImageBuilderSpur50-class>>#forArchitecture: architecture

�� | candidates |

�� candidates := self subclasses select: [ :sc | sc name endsWith: architecture, 'bit' ].

�� candidates��

�� ifEmpty: [ self error: 'No candidates for architecture: ', architecture ].

�� candidates size > 1

�� ifTrue: [ self error: 'More than one candidate for architecture: ', architecture ].

�� ^ candidates anyOne new

�� PBImageBuilderSpur50 >>#initialize

�� super initialize.

�� statistics := PBBootstrapStatistics new.

�� logger := PBBootstrapLogger new.

�� imageFileReference := 'bootstrap.image' asFileReference.

�� "the default espell backend for the bootstrap"

�� self initializeBackend.��

�� self instantiateClassLoader.��

ahh, there is the reference to "bootstrap.image"

So just to round out a high level overview, the last two messages sent are defined as...

�� PBImageBuilderSpur5032bit>>#initializeBackend

�� espellBackend := EPSimulatorBackend for32Bit forBootstrap��

which I won't dig further but the class seems available at��[8]

and Espell is described briefly at [9] (but what is a "MOP"? the term is not defined there)

�� PBImageBuilderSpur50>>#instantiateClassLoader

�� classLoader := PBSpurClassLoader new.��

which is defined at [10], and��there is an interesting example at [11].

[3]��https://github.com/pharo-project/pharo/blob/development/bootstrap/scripts/3-prepare.sh

[4] https://github.com/pharo-project/pharo/blob/development/bootstrap/scripts/prepare_image.st

[5]��https://github.com/pharo-project/pharo/blob/development/bootstrap/scripts/bootstrap.st

[6]��https://github.com/pharo-project/pharo/blob/development/bootstrap/src/Pharo30Bootstrap.package/PBBootstrap.class/class/fromCommandLine.st

[7]��https://github.com/pharo-project/pharo/blob/development/bootstrap/src/Pharo30Bootstrap.package/PBBootstrap.class/instance/bootstrap.st

[8]��https://github.com/guillep/espell/blob/master/src/EspellSimulator.package/EPSimulatorBackend.class/class/for32Bit.st

[9]��https://rmod.inria.fr/archives/papers/Poli15a-Onward-Bootstrapping.pdf

[10]��https://github.com/pharo-project/pharo/tree/development/bootstrap/src/Pharo30Bootstrap.package/PBSpurClassLoader.class

[11]��https://github.com/pharo-project/pharo/blob/development/bootstrap/src/Pharo30Bootstrap.package/PBImageBuilderSpur50.class/class/example5617.st

So now I guess that bootstrap.image has been generated?

Just curious, what is the size of this file right now, before the next step?

Perhaps an `ls -l` could echo this to the build log.

The penultimate major CI step seems to then start adding packages to bootstrap.image...

+ BUILD_NUMBER=822 BOOTSTRAP_ARCH=32 bash ./bootstrap/scripts/4-build.sh��

located at [12] and searching on "${VM}" is enlightening.

Its help information says...

Pharo Build Script

�� ==================

�� This script assumes the existence of a new uninitialized image. Then it proceeds to its initialization and \"growing\".

�� * Step 1:

�� - Initialize the image

�� - output: core.image

�� * Step 2:

�� - Bootstrap Monticello local repositories

�� - output: monticello_bootstrap.image and changes file

�� * Step 3:

�� - Load Monticello remote repositories

�� - output: monticello.image and changes file

�� * Step 4:

�� - Load Metacello

�� - output: metacello.image and changes file

�� * Step 5:

�� - Load the rest of the image using BaselineOfIDE

�� - output: Pharo.image and changes file

Unfortunately those steps are labelled in the script,

but the first action shown in the log is...

�� cp bootstrap.image Pharo7.0-compiler-32bit-9912d7c.image��

Initializing Bootstraped Image

�� pharo --headless Pharo7.0-compiler-32bit-9912d7c.image

[12]��https://github.com/pharo-project/pharo/blob/development/bootstrap/scripts/4-build.sh

The final major CI step was a fair way past what I was interested in right now. ...

+ BUILD_NUMBER=822 bash ../bootstrap/scripts/prepare_for_upload.sh

cheers -ben