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| author | Valentin Gagarin <valentin.gagarin@tweag.io> | 2022-09-19 22:21:40 +0200 |
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| committer | Valentin Gagarin <valentin.gagarin@tweag.io> | 2022-11-09 01:29:01 +0100 |
| commit | be8744f937150c65ffa5d98ffdc74c502dbcdd5e (patch) | |
| tree | c331f632990e12035e384ed4b58f1be298b95fec /doc/manual/src/architecture | |
| parent | 37358d0bcfd8fa38b7f652c837b8e9204a3c43f9 (diff) | |
manual: architecture overview
these changes were not merged properly and had to be reverted.
see merge commit d8e54d19f71f78540dd967b2e42be6a5d8a0b1bb for full
history leading up to here.
Diffstat (limited to 'doc/manual/src/architecture')
| -rw-r--r-- | doc/manual/src/architecture/architecture.md | 77 |
1 files changed, 77 insertions, 0 deletions
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 ]----------------' : | +| : : | +| :............................................: | ++----------------------------------------------------------------------------------+ +``` + |