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diff --git a/doc/manual/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in index 908e7e3d9..b386aa14b 100644 --- a/doc/manual/src/SUMMARY.md.in +++ b/doc/manual/src/SUMMARY.md.in @@ -59,6 +59,7 @@ @manpages@ - [Files](command-ref/files.md) - [nix.conf](command-ref/conf-file.md) +- [Architecture](architecture/architecture.md) - [Glossary](glossary.md) - [Contributing](contributing/contributing.md) - [Hacking](contributing/hacking.md) diff --git a/doc/manual/src/architecture/architecture.md b/doc/manual/src/architecture/architecture.md new file mode 100644 index 000000000..24150fc2b --- /dev/null +++ b/doc/manual/src/architecture/architecture.md @@ -0,0 +1,77 @@ +# Architecture + +This chapter describes how Nix works. +It should help users understand why Nix behaves as it does, and it should help developers understand how to modify Nix and how to write similar tools. + +## Overview + +Nix consists of [hierarchical layers]. + +[hierarchical layers]: https://en.m.wikipedia.org/wiki/Multitier_architecture#Layers + +``` ++---------------------------------------------------------------+ +| Nix | +| [ commmand line interface ]------, | +| | | | +| evaluates | | +| | manages | +| V | | +| [ configuration language ] | | +| | | | +| +----------------------------|-------------------V----------+ | +| | store evaluates to | | +| | | | | +| | referenced by V builds | | +| | [ build input ] ---> [ build plan ] ---> [ build result ] | | +| | | | +| +-----------------------------------------------------------+ | ++---------------------------------------------------------------+ +``` + +At the top is the [command line interface](../command-ref/command-ref.md), translating from invocations of Nix executables to interactions with the underlying layers. + +Below that is the [Nix language](../language/index.md), a [purely functional] configuration language. +It is used to compose expressions which ultimately evaluate to self-contained *build plans*, used to derive *build results* from referenced *build inputs*. + +[purely functional]: https://en.m.wikipedia.org/wiki/Purely_functional_programming + +Command line interface and Nix language are what users interact with most. + +> **Note** +> The Nix language itself does not have a notion of *packages* or *configurations*. +> As far as we are concerned here, the inputs and results of a build plan are just data. + +Underlying these is the [Nix store](../glossary.md#gloss-store), a mechanism to keep track of build plans, data, and references between them. +It can also execute build plans to produce new data. + +A build plan is a series of *build tasks*. +Each build task has a special build input, which is used as *build instructions*. +The result of a build task can be input to another build task. + +> **Important** +> A build task in Nix is called [derivation](../glossary#gloss-derivation). + +``` ++----------------------------------------------------------------------------------+ +| store .............................................. | +| : build plan : | +| : : | +| [ build input ]---instructions-, : | +| : | : | +| : v : | +| [ build input ]--------->[ build task ]-instructions-, : | +| : | : | +| : v : | +| [ build input ]---instructions-, [ build task ]--->[ build result ] | +| : | ^ : | +| : v | : | +| [ build input ]--------->[ build task ]--------------' : | +| : ^ : | +| : | : | +| [ build input ]----------------' : | +| : : | +| :............................................: | ++----------------------------------------------------------------------------------+ +``` + |