Re: [RFC] v2 Documentation: dependencies specification in Bitbake and Debian

["Cirujano Cuesta, Silvano" <silvano.cirujano-cuesta@siemens.com>]

On Wed, 2019-04-03 at 10:32 +0200, Maxim Yu. Osipov wrote:
> Hi Silvano,
> 
> On 4/3/19 10:24 AM, Cirujano Cuesta, Silvano wrote:
> > Hi Maxim,
> > 
> > Thank you for the information!
> > I'm sorry, in the hurry I just concentrated in the content and not that much in the format of the e-mail.
> > I've just used wrongly my corporate e-mail client (Evolution) and
> > copy&paste.
> > But I know in general how to do it properly both with Evolution [1] and send-email and pay more attention when contributing code intended to be merged.
> > 
> > I found a cover letter overkilling and therefore I intended to put my message in the part of the diff being ignored (after '---' and before the files list).
> > The contribution guide mentions a cover letter associated to patch series, but I still find it a bit overkilling for such a RFC.
> > 
> > BTW I didn't find any information in the contribution guide about the 'scissors format' for providing some text to be ignored.
> > Is is accepted for single patch contributions?
> 
> Sure - send it in 'scissors format' if you find it more appropriate for 
> your patch. We are not "strict cover letter" purists :)

Ups, cutting above the 'scissors' is not the default for 'git am' :-/
I'll therefore stick for this RFC and future RFCs and Patches to the established workflow with cover letter.

Regards,
  Silvano

> 
> Thanks,
> Maxim.
> 
> > I still see the advantage of a cover letter for patch series.
> > 
> > Cheers,
> >    Silvano
> > 
> > [1] https://www.kernel.org/doc/html/v5.0/process/email-clients.html?highlight=evolution#evolution-gui
> > 
> > On Wed, 2019-04-03 at 09:19 +0200, Maxim Yu. Osipov wrote:
> > > Hi Silvano,
> > > 
> > > I've tried to apply your patch but 'git am' complains about malformed line.
> > > 
> > > Please have a look in the section Formatting Patches in
> > > https://github.com/ilbers/isar/blob/next/CONTRIBUTING.md
> > > 
> > > Personally I use the following sequence of commands when submitting the
> > > patch (f.e. v2) to the mailing list:
> > > 
> > > git format-patch --cover-letter --subject-prefix="PATCH v2" -o out -1
> > > vim out/0000-cover-letter.patch
> > > git send-email --suppress-cc=all --to isar-users@googlegroups.com out/*
> > > 
> > > In cover letter people usually mention differences versus previous
> > > patch series version and other stuff which shouldn't go into the commit
> > > message.
> > > 
> > > 
> > > Thanks,
> > > Maxim.
> > > 
> > > 
> > > On 3/29/19 2:17 PM, Cirujano Cuesta, Silvano wrote:
> > > > Reposting my first message on this thread adding the patch for mailing list review.
> > > > 
> > > > 
> > > > After my first try a couple of weeks ago, I'm coming back with a new try to improve the documentation.
> > > > 
> > > > I've taken Claudius feedback into account (thank you again for your very valuable input!).
> > > > And I let two colleagues of mine with a similar superficial/deep knowledge of ISAR review it.
> > > > 
> > > > Right now it's everything in a single MarkDown document, but I'd rather put the section "Dependency specification variables" into a separate document.
> > > > I keep it together right now to simplify the reviews.
> > > > 
> > > > For those of you who like to have some comfort in life, I've pushed the document to a fork of ISAR in my personal area.
> > > > That way you can take advantage of MarkDown conversion to HTML and rendering going to [1] ;-)
> > > > 
> > > > [1] https://github.com/Silvanoc/isar/blob/silvano/dependencies-documentation/doc/dependencies.md
> > > > 
> > > > Signed-off-by: Silvano Cirujano Cuesta <silvano.cirujano-cuesta@siemens.com>
> > > > ---
> > > >    doc/dependencies.md | 255 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >    1 file changed, 255 insertions(+)
> > > >    create mode 100644 doc/dependencies.md
> > > > 
> > > > diff --git a/doc/dependencies.md b/doc/dependencies.md
> > > > new file mode 100644
> > > > index 0000000..390e677
> > > > --- /dev/null
> > > > +++ b/doc/dependencies.md
> > > > @@ -0,0 +1,255 @@
> > > > +# Dependency management in ISAR
> > > > +
> > > > +## Introduction
> > > > +
> > > > +The typical goal of an ISAR build is to obtain:
> > > > +
> > > > +1. a disk image containing one or more partition images (all optional),
> > > > +1. containing one or more Debian root filesystems with
> > > > +1. certain Debian packages installed.
> > > > +
> > > > +Reaching this goal relies on the availability of the above listed elements on *runtime*, the specification of the **[runtime environments](#runtime-environment-specification)** helps the
> > > > different
> > > > build tools ensuring the availability of the mentioned elements on runtime.
> > > > +
> > > > +Usually some of the runtime dependencies have to be built, and it happens in special environments. These **[buildtime environments](#buildtime-environment-specification)** help the different
> > > > build
> > > > tools preparing the environment for building the runtime dependencies.
> > > > +
> > > > +The differentiation between buildtime and runtime environments is very important.
> > > > +The fact that ISAR uses Debian both for buildtime and runtime environments might mislead some people.
> > > > +In general the names of the variables being used to specify those dependencies aren't supporting this differentiation, but difficulting it.
> > > > +
> > > > +Not only the build environments have to be specified, but also the **[build process](#build-process-specification)** that takes care of building and integrating both the runtime dependencies
> > > > and
> > > > the
> > > > buildtime dependencies.
> > > > +
> > > > +## Runtime environment specification
> > > > +
> > > > +As mentioned above, ISAR can build [partitioned disk images](#disk-image) or only [root filesystems](#root-filesystem).
> > > > +
> > > > +Let's first analyze how the content of the different runtime containers can be specified from bigger to smaller container.
> > > > +
> > > > +```
> > > > ++---------------------------------------------------------------------------------------------------+
> > > > +|                                                                                                   |
> > > > +|    DISK IMAGE                                                                                     |
> > > > +|                                                                                                   |
> > > > +|   +------------+   +-----------------------------------+   +------------------------------+       |
> > > > +|   |            |   |                                   |   |                              ||      |
> > > > +|   | Bootloader |   | Bootable partition                |   | Other partitions             |||     |
> > > > +|   |            |   |                                   |   |                              ||||    |
> > > > +|   |            |   | +------------------------------+  |   |                              ||||    |
> > > > +|   |            |   | |                              |  |   |                              ||||    |
> > > > +|   |            |   | |  ROOT FILESYSTEM             |  |   |                              ||||    |
> > > > +|   +------------+   | |                              |  |   |                              ||||    |
> > > > +|                    | |    +-------------------+     |  |   |                              ||||    |
> > > > +|                    | |    |                   | |   |  |   |                              ||||    |
> > > > +|                    | |    |  DEBIAN PACKAGES  | |   |  |   |                              ||||    |
> > > > +|                    | |    |                   | |   |  |   |                              ||||    |
> > > > +|                    | |    |                   | |   |  |   |                              ||||    |
> > > > +|                    | |    |                   | |   |  |   |                              ||||    |
> > > > +|                    | |    +-------------------+ |   |  |   |                              ||||    |
> > > > +|                    | |     ---------------------+   |  |   |                              ||||    |
> > > > +|                    | |                              |  |   +------------------------------+|||    |
> > > > +|                    | +------------------------------+  |    -------------------------------+||    |
> > > > +|                    |                                   |    --------------------------------+|    |
> > > > +|                    +-----------------------------------+     --------------------------------+    |
> > > > +|                                                                                                   |
> > > > ++---------------------------------------------------------------------------------------------------+
> > > > +```
> > > > +
> > > > +### Disk image
> > > > +
> > > > +A disk image depends on:
> > > > +
> > > > +1. a bootloader (optional) and
> > > > +1. one or more partitions, containing one of them a [root filesystem](#root-filesystem).
> > > > +
> > > > +The ISAR way to **specify** them is through *WKS files* (OpenEmbedded KickStart files).
> > > > +ISAR doesn't change it in any significant way, therefore the corresponding [Yocto documentation][wks] provides the best reference.
> > > > +
> > > > +### Root filesystem
> > > > +
> > > > +A root filesystem depends on:
> > > > +
> > > > +1. a minimal set of files (the result of `debootstrap`) and
> > > > +1. additional files and configurations obtained from *Debian packages*.
> > > > +
> > > > +The ISAR way to **specify** them is quite complex and involves *ISAR variables* that can be found in configuration files or recipes and artifacts and metadata being provided by *Debian
> > > > packages*.
> > > > +
> > > > +See following sections for more information about how to specify the content of the root filesystem:
> > > > +
> > > > +* [ISAR `IMAGE_INSTALL` variable](#isar-image_install-variable)
> > > > +* [ISAR `IMAGE_PREINSTALL` variable](#isar-image_preinstall-variable)
> > > > +* [ISAR `DEBIAN_DEPENDS` variable](#isar-debian_depends-variable)
> > > > +* [Debian `Depends` control-file value](#debian-depends-control-file-value)
> > > > +
> > > > +## Buildtime environment specification
> > > > +
> > > > +The creation of the [above mentioned runtime units](#runtime-environment-specification) (disk images, bootloaders, root filesystems, packages, ...) takes place in different environments.
> > > > +
> > > > +These environments have to be specified.
> > > > +
> > > > +### Buildchroot
> > > > +
> > > > +The *Debian packages* are built in the so-called *buildchroot* filesystem.
> > > > +
> > > > +It's a Debian chroot that is used to build custom Debian packages required by the **[root filesystem](#root-filesystem)**.
> > > > +This build environment depends on the presence of certain artifacts (compilers, configurations, linkers, ...).
> > > > +
> > > > +The ISAR way to **specify** them is quite complex and involves *ISAR variables* that can be found in configuration files or recipes and artifacts and metadata being provided by *Debian
> > > > packages*.
> > > > +
> > > > +See following sections for more information about how to specify the content of the chroot:
> > > > +
> > > > +* [ISAR `IMAGER_INSTALL` variable](#isar-image_install-variable)
> > > > +* [ISAR `BUILDCHROOT_PREINSTALL` variable](#isar-buildchroot_preinstall-variable)
> > > > +* [Debian `Build-Depends` control-file value](#debian-build-depends-control-file-value)
> > > > +
> > > > +If a disk image is being created, the same environment is being used for building the image.
> > > > +For this usage additional dependencies might appear. See the [imager](#imager) section for more information.
> > > > +
> > > > +### Imager
> > > > +
> > > > +The *disk images* are built in the so-called *imager*.
> > > > +
> > > > +It's a Debian chroot that is used to build **[disk images](#disk-image)**.
> > > > +This build environment depends on the presence of certain artifacts (compilers, configurations, linkers, ...).
> > > > +Although conceptually the imager doesn't have anything to do with the buildchroot, in the implementation the same chroot is being used for both tasks.
> > > > +
> > > > +The ISAR way to **specify** them involves *ISAR variables* that can be found in configuration files or recipes.
> > > > +
> > > > +See following sections for more information about how to specify the content of the chroot:
> > > > +
> > > > +* [ISAR `WIC_IMAGER_INSTALL` variable](#isar-wic_imager_install-variable)
> > > > +* [ISAR `IMAGER_BUILD_DEPS` variable](#isar-imager_build_deps-variable)
> > > > +
> > > > +### Target filesystem
> > > > +
> > > > +It's a Debian root filesystem that results from creating a minimalistic Debian skeleton via `debootstrap` and installing Debian packages on it, resulting in the [root filesystem](#root-
> > > > filesystem).
> > > > +
> > > > +There's no need to **specify** this build environment, since it's the [root filesystem of the runtime environment](#root-filesystem).
> > > > +
> > > > +## Build process specification
> > > > +
> > > > +ISAR relies on a subset of Bitbake to take care of the build process.
> > > > +Therefore the ISAR way to **specify** the different tasks involved in the process is Bitbake recipes with some *Bitbake variables* (well documented ) and some *ISAR variables* (some of them
> > > > are
> > > > only
> > > > syntactic sugar).
> > > > +
> > > > +See following sections for more information about how to specify inter-tasks dependencies:
> > > > +
> > > > +* [Bitbake `DEPENDS` variable](#bitbake-depends-variable)
> > > > +* [ISAR `IMAGE_INSTALL` variable](#isar-image_install-variable)
> > > > +* [ISAR `IMAGER_BUILD_DEPS` variable](#isar-imager_build_deps-variable)
> > > > +
> > > > +## Mapping: Variables <=> Build environment and Stages
> > > > +
> > > > +| Variable | Environment | Stage |
> > > > +|:-------- |:-----------------:|:-----:|
> > > > +| [`DEPENDS`](#bitbake-depends-variable) | | All |
> > > > +| [`IMAGE_INSTALL`](#isar-image_install-variable) | [Root filesystem](#root-filesystem) | [Root filesystem](#root-filesystem) preparation and build |
> > > > +| [`IMAGE_PREINSTALL`](#isar-image_preinstall-variable) | [Root filesystem](#root-filesystem) | |
> > > > +| [`DEBIAN_DEPENDS`](#isar-debian_depends-variable) | [Root filesystem](#root-filesystem) | |
> > > > +| [`Depends` control-file](#debian-depends-control-file-value) | [Root filesystem](#root-filesystem) | |
> > > > +| [`IMAGE_TRANSIENT_PACKAGES`](#isar-image_transient_packages-variable) | [Root filesystem](#root-filesystem) | [Root filesystem](#root-filesystem) preparation and build |
> > > > +| [`BUILDCHROOT_PREINSTALL`](#isar-buildchroot_preinstall-variable) | [Buildchroot](#buildroot) | |
> > > > +| [`Build-Depends` control-file](#debian-build-depends-control-file-value) | [Buildchroot](#buildroot) | |
> > > > +| [`IMAGER_BUILD_DEPS`](#isar-imager_build_deps-variable) | | [Imager](#imager) preparation |
> > > > +| [`IMAGER_INSTALL`](#isar-imager_install-variable) | [Imager](#imager) | |
> > > > +| [`WIC_IMAGER_INSTALL`](#isar-wic_imager_install-variable) | [Imager](#imager) | |
> > > > +
> > > > +## Dependencies specification variables
> > > > +
> > > > +### Bitbake `DEPENDS` variable
> > > > +
> > > > +This is a **Bitbake** variable that specifies **Bitbake inter-task dependencies**.
> > > > +
> > > > +Since it specifies the recipes that another recipe depend upon, this variable can be specified in **package recipes** and **image recipes**.
> > > > +
> > > > +### ISAR `IMAGE_INSTALL` variable
> > > > +
> > > > +This is originally a **Bitbake** variable that has conceptually the same goal in ISAR as in Yocto.
> > > > +In the case of ISAR it specifies at the same time **Bitbake inter-task dependencies** and **image custom Debian package dependencies**.
> > > > +
> > > > +It basically specifies that a **[root filesystem](#root-filesystem)** (the prefix 'IMAGE' can be misleading here) requires a custom Debian package.
> > > > +But since custom Debian packages are being built from package recipes, this variable also specifies that an image recipe depends on package recipes.
> > > > +
> > > > +For this "magic" to work both the Debian package and the package recipe have to have the same name.
> > > > +Something else than this 1:1 behaviour (e.g. a recipe creating multiple Debian binary packages out of a single Debian source package) requires some hacking out of the scope of this document.
> > > > +
> > > > +This variable can be found in **configuration files** and **image recipes**.
> > > > +
> > > > +### ISAR `IMAGE_PREINSTALL` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **image upstream Debian package dependencies**.
> > > > +
> > > > +It specifies that a **[root filesystem](#root-filesystem)** requires certain *upstream Debian packages*, being "upstream Debian packages" ready built packages that can be downloaded from a
> > > > Debian
> > > > package repository.
> > > > +
> > > > +This variable can be found in **configuration files** and **image recipes**.
> > > > +
> > > > +### ISAR `DEBIAN_DEPENDS` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **Debian inter-package dependencies** and can be used only on package recipes inheriting from the **`dpkg-raw` class**.
> > > > +
> > > > +It lists the Debian binary packages that a custom Debian package depends upon.
> > > > +It can be used for both upstream and custom packages.
> > > > +It results in an entry in the corresponding **[Debian `Depends` control-file value](#debian-depends-control-file-value)**.
> > > > +
> > > > +A common usage is for creating meta-packages that only keep dependencies on further packages synchronized.
> > > > +
> > > > +This variable can be found in **package recipes**.
> > > > +
> > > > +### ISAR `IMAGE_TRANSIENT_PACKAGES` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **image custom Debian package dependencies** and **Bitbake inter-task dependencies**.
> > > > +
> > > > +This is a variable that is rarely needed and only for a very specific use case!
> > > > +That is when a package is needed in the **[root filesystem](#root-filesystem)** during the **root filesystem build stage**, but not in the final **[root filesystem](#root-filesystem)**.
> > > > +Meaning that the installation is only transient, therefore its name.
> > > > +
> > > > +This variable can be found in **configuration files** and **image recipes**.
> > > > +
> > > > +### Debian `Depends` control-file value
> > > > +
> > > > +This is an **Debian** variable that specifies **Debian inter-package dependencies**.
> > > > +
> > > > +`Depends` specifies the Debian packages that are required in the [runtime environment](#runtime-environment-specification) by the package declaring the dependencies.
> > > > +
> > > > +It relies on standard Debian mechanisms, therefore the corresponding [official Debian documentation][pkg-rels] provides the best reference.
> > > > +
> > > > +### ISAR `BUILDCHROOT_PREINSTALL` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **buildchroot Debian package dependencies**.
> > > > +
> > > > +It specifies that **[buildchroot](#buildroot)** requires certain *Debian packages*.
> > > > +
> > > > +This variable can be found in **buildchroot recipes**.
> > > > +
> > > > +### Debian `Build-Depends` control-file value
> > > > +
> > > > +This is an **Debian** variable that specifies **Debian inter-package dependencies**.
> > > > +
> > > > +`Build-Depends` specifies the Debian packages that are required in the [buildtime environment](#buildtime-environment-specification) to build the package declaring the dependencies.
> > > > +
> > > > +It relies on standard Debian mechanisms, therefore the corresponding [official Debian documentation][pkg-rels] provides the best reference.
> > > > +
> > > > +### ISAR `IMAGER_BUILD_DEPS` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **Bitbake inter-task dependencies**.
> > > > +
> > > > +It has exactly the same effect as `DEPENDS`.
> > > > +It simply provides syntactic sugar to separate dependencies on recipes for building the runtime environment from dependencies on recipes for building the **[imager](#imager)**.
> > > > +
> > > > +This variable can be found in **configuration files**.
> > > > +
> > > > +### ISAR `IMAGER_INSTALL` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **imager Debian package dependencies**.
> > > > +
> > > > +It specifies that certain *Debian packages* have to be installed on the **[imager](#imager)**.
> > > > +
> > > > +This variable can be found typically in **configuration files**, although it could also be part of **image recipes**.
> > > > +
> > > > +### ISAR `WIC_IMAGER_INSTALL` variable
> > > > +
> > > > +This is an **ISAR-only** variable that specifies **imager Debian package dependencies**.
> > > > +
> > > > +It specifies that an **[imager](#imager)** requires certain *Debian packages* so that WIC can build the disk images (e.g. `parted`).
> > > > +
> > > > +This variable can be found typically in **configuration files**, although it could also be part of **image recipes**.
> > > > +
> > > > +[wks]: https://www.yoctoproject.org/docs/current/ref-manual/ref-manual.html#ref-kickstart "OpenEmbedded Kickstart (.wks) Reference"
> > > > +[pkg-rels]: https://www.debian.org/doc/debian-policy/ch-relationships.html "Debian policy: Declaring relationships between packages"
> > > > -- 
> > > > 2.11.0
> > > > 
> > > 
> > > 
> > > -- 
> > > Maxim Osipov
> > > ilbers GmbH
> > > Maria-Merian-Str. 8
> > > 85521 Ottobrunn
> > > Germany
> > > +49 (151) 6517 6917
> > > mosipov@ilbers.de
> > > http://ilbers.de/
> > > Commercial register Munich, HRB 214197
> > > General Manager: Baurzhan Ismagulov
> > > 
> 
> 
-- 
With best regards,
Silvano Cirujano Cuesta

Siemens AG
Smart Embedded Systems
Mobile: +49 173 3181462
mailto:silvano.cirujano-cuesta@siemens.com