2020-05-19 18:20:18 +02:00
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title = "Self Hosting Fedora Base"
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date = 2014-01-14T16:15:52+00:00
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2023-10-26 11:53:38 +02:00
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[taxonomies]
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tags = ["fedora", "bootstrap", "buildroot"]
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2020-05-19 18:20:18 +02:00
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If you want to bootstrap a distribution or want to rebuild it from the sources (SRPMS) to get the same
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binaries (think CentOS), you have to build the build tools and rebuild them with the built build tools,
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which have to be built with other build tools…
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My goal for a self-hosting Fedora Base is to reduce the number of packages to do such a rebuild.
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<!-- more -->
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The first step is to get the packages to build the most important component for a linux distribution - the kernel.
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To get those packages, Phil Knirsch wrote a small python script, which calls `repoquery`.
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I extended this script to output graphviz .dot formatted files.
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The first run gives us [1806 packages](https://harald.fedorapeople.org/kernel-br-all.txt), with which you could build
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the tools to build the tools to […] build the kernel, if you manage to break the dependency cycle, etc.
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If you want to display this beast with e.g. "sfdp" and "gvmap" from the graphviz suite, this will give you a monster graph.
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[<img alt="Self-Hosting kernel build requirements" src="https://harald.fedorapeople.org/kernel-br-all.png" height="333" width="800" />](https://harald.fedorapeople.org/kernel-br-all.svg)
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Self-Hosting kernel build requirements
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This was generated with the [kernel-br-all.dot](https://harald.fedorapeople.org/kernel-br-all.dot) file and the command:
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```console
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$ START=7; cat kernel-br-all.dot | \
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sfdp -Gstart=$START -Goverlap=prism | \
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gvmap -e -d $START | \
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neato -Gstart=$START -n2 -Ecolor=#44444455 -Tsvg \
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> kernel-br-all.svg
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```
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My next step was to identify the source of weird build requirements like `qt`, `kdelibs` or `wayland`.
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So I build a list of packages, which might be removed from the build requirements, because they only build documentation
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or willingly add a build requirement to a graphical component like X, wayland or a GUI.
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After filtering those with [the python script](https://harald.fedorapeople.org/buildreq.py), the resulting graph was
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mainly dominated by perl packages, so I just merged them in one "perl" node. The graph from this is almost readable.
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[<img alt="Reduced Self-Hosting kernel build requirements" src="https://harald.fedorapeople.org/kernel-br-reduced.png" height="525" width="800" />](https://harald.fedorapeople.org/kernel-br-reduced.svg)
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Reduced Self-Hosting kernel build requirements
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`graphviz` comes with `tred`, which reduces the graph, so that at least one path leads from X to Y.
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With this reduction we get a nice graph generated from
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[kernel-br-reduced.dot](https://harald.fedorapeople.org/kernel-br-reduced.dot) by:
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```console
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$ START=7; tred kernel-br-reduced.dot | \
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sfdp -Gstart=$START -Goverlap=prism | \
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gvmap -e -d $START | \
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neato -Gstart=$START -n2 -Ecolor=#44444455 -Tsvg \
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> kernel-br-reduced-tred.svg
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```
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Now, most of the build requirements are missing, but one path, so you can at least find **one** package,
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which requires a specific package. All the red nodes in the graph are the build requirements, for which no
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build requirements were added. So the strategy should be to get rid of those, or make sure they don't pull in the #
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complete distribution. We might want to use the pre-built documentation shipped with the package or have a separate
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documentation build phase with the same source. For other packages, we might have to split out the GUI components.
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If you have other ideas, I am happy to get to know them.
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**Conclusion: 188 packages plus all the perl packages could form a basic buildroot to build itsself.
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To achieve this, we have to take care of those 56 red packages, that these are not used.**
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The list of the 65 spec files with the build requirements to ifdef can be found here:
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[http://harald.fedorapeople.org/bootstrap-not-needed-deps.txt](https://harald.fedorapeople.org/bootstrap-not-needed-deps.txt)
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[<img alt="" src="https://harald.fedorapeople.org/kernel-br-reduced-tred.svg" width="800" />](https://harald.fedorapeople.org/kernel-br-reduced-tred.svg)
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Reduced Build Requirements for the package kernel
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