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diff --git a/doc/manual/src/architecture/architecture.md b/doc/manual/src/architecture/architecture.md new file mode 100644 index 000000000..b17eacd2e --- /dev/null +++ b/doc/manual/src/architecture/architecture.md @@ -0,0 +1,42 @@ +# 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](https://en.m.wikipedia.org/wiki/Multitier_architecture#Layers). + +``` + [ commmand line interface ] + | + | evaluates + V + [ configuration language ] + | + | evaluates to + | + reference V build +[ build inputs ] --> [ build plans ] --> [ build results ] + \ | / + \ | persisted to / + \ V / + [ store ] +``` + +At the top is the *command line interface*, translating from invocations of Nix executables to interactions with the underlying layers. + +Below that is the *Nix language*, a [purely functional](https://en.m.wikipedia.org/wiki/Purely_functional_programming) configuration language. +It is used to compose expressions which ultimately evaluate to self-contained *build steps*, used to derive *build results* from referenced *build inputs*. + +::: {.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 derivation are just data. +In practice this amounts to a set of files in a file system. +::: + +The command line and Nix language are what users interact with most. + +Underlying everything is the *Nix store*, a mechanism to keep track of build plans, data, and references between them. +It can also execute *build instructions*, captured in the build plans, to produce new data. + |