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diff --git a/doc/manual/src/architecture/store/store.md b/doc/manual/src/architecture/store/store.md deleted file mode 100644 index 08b6701d5..000000000 --- a/doc/manual/src/architecture/store/store.md +++ /dev/null @@ -1,151 +0,0 @@ -# Store - -A Nix store is a collection of *store objects* with references between them. -It supports operations to manipulate that collection. - -The following concept map is a graphical outline of this chapter. -Arrows indicate suggested reading order. - -``` - ,--------------[ store ]----------------, - | | | - v v v - [ store object ] [ closure ]--, [ operations ] - | | | | | | - v | | v v | - [ files and processes ] | | [ garbage collection ] | - / \ | | | - v v | v v -[ file system object ] [ store path ] | [ derivation ]--->[ building ] - | ^ | | | - v | v v | - [ digest ]----' [ reference scanning ]<------------' - / \ - v v -[ input addressing ] [ content addressing ] -``` - -## Store Object - -A store object can hold - -- arbitrary *data* -- *references* to other store objects. - -Store objects can be build inputs, build results, or build tasks. - -Store objects are [immutable][immutable-object]: once created, they do not change until they are deleted. - -## Reference - -A store object reference is an [opaque][opaque-data-type], [unique identifier][unique-identifier]: -The only way to obtain references is by adding or building store objects. -A reference will always point to exactly one store object. - -## Operations - -A Nix store can *add*, *retrieve*, and *delete* store objects. - - [ data ] - | - V - [ store ] ---> add ----> [ store' ] - | - V - [ reference ] - -<!-- --> - - [ reference ] - | - V - [ store ] ---> get - | - V - [ store object ] - -<!-- --> - - [ reference ] - | - V - [ store ] --> delete --> [ store' ] - - -It can *perform builds*, that is, create new store objects by transforming build inputs into build outputs, using instructions from the build tasks. - - - [ reference ] - | - V - [ store ] --> build --(maybe)--> [ store' ] - | - V - [ reference ] - - -As it keeps track of references, it can [garbage-collect][garbage-collection] unused store objects. - - - [ store ] --> collect garbage --> [ store' ] - -## Files and Processes - -Nix maps between its store model and the [Unix paradigm][unix-paradigm] of [files and processes][file-descriptor], by encoding immutable store objects and opaque identifiers as file system primitives: files and directories, and paths. -That allows processes to resolve references contained in files and thus access the contents of store objects. - -Store objects are therefore implemented as the pair of - - - a [file system object](fso.md) for data - - a set of [store paths](path.md) for references. - -[unix-paradigm]: https://en.m.wikipedia.org/wiki/Everything_is_a_file -[file-descriptor]: https://en.m.wikipedia.org/wiki/File_descriptor - -The following diagram shows a radical simplification of how Nix interacts with the operating system: -It uses files as build inputs, and build outputs are files again. -On the operating system, files can be run as processes, which in turn operate on files. -A build function also amounts to an operating system process (not depicted). - -``` -+-----------------------------------------------------------------+ -| Nix | -| [ commmand line interface ]------, | -| | | | -| evaluates | | -| | manages | -| V | | -| [ configuration language ] | | -| | | | -| +-----------------------------|-------------------V-----------+ | -| | store evaluates to | | -| | | | | -| | referenced by V builds | | -| | [ build input ] ---> [ build plan ] ---> [ build result ] | | -| | ^ | | | -| +---------|----------------------------------------|----------+ | -+-----------|----------------------------------------|------------+ - | | - file system object store path - | | -+-----------|----------------------------------------|------------+ -| operating system +------------+ | | -| '------------ | | <-----------' | -| | file | | -| ,-- | | <-, | -| | +------------+ | | -| execute as | | read, write, execute | -| | +------------+ | | -| '-> | process | --' | -| +------------+ | -+-----------------------------------------------------------------+ -``` - -There exist different types of stores, which all follow this model. -Examples: -- store on the local file system -- remote store accessible via SSH -- binary cache store accessible via HTTP - -To make store objects accessible to processes, stores ultimately have to expose store objects through the file system. - |