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diff --git a/doc/manual/src/glossary.md b/doc/manual/src/glossary.md index c916af4bc..b7c340d36 100644 --- a/doc/manual/src/glossary.md +++ b/doc/manual/src/glossary.md @@ -1,219 +1,275 @@ # Glossary - - [derivation]{#gloss-derivation}\ - A description of a build task. The result of a derivation is a - store object. Derivations are typically specified in Nix expressions - using the [`derivation` primitive](./language/derivations.md). These are - translated into low-level *store derivations* (implicitly by - `nix-env` and `nix-build`, or explicitly by `nix-instantiate`). +- [derivation]{#gloss-derivation} - [derivation]: #gloss-derivation + A description of a build task. The result of a derivation is a + store object. Derivations are typically specified in Nix expressions + using the [`derivation` primitive](./language/derivations.md). These are + translated into low-level *store derivations* (implicitly by + `nix-env` and `nix-build`, or explicitly by `nix-instantiate`). - - [store derivation]{#gloss-store-derivation}\ - A [derivation] represented as a `.drv` file in the [store]. - It has a [store path], like any [store object]. + [derivation]: #gloss-derivation - Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv` +- [store derivation]{#gloss-store-derivation} - See [`nix show-derivation`](./command-ref/new-cli/nix3-show-derivation.md) (experimental) for displaying the contents of store derivations. + A [derivation] represented as a `.drv` file in the [store]. + It has a [store path], like any [store object]. - [store derivation]: #gloss-store-derivation + Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv` - - [instantiate]{#gloss-instantiate}, instantiation\ - Translate a [derivation] into a [store derivation]. + See [`nix derivation show`](./command-ref/new-cli/nix3-derivation-show.md) (experimental) for displaying the contents of store derivations. - See [`nix-instantiate`](./command-ref/nix-instantiate.md). + [store derivation]: #gloss-store-derivation - [instantiate]: #gloss-instantiate +- [instantiate]{#gloss-instantiate}, instantiation - - [realise]{#gloss-realise}, realisation\ - Ensure a [store path] is [valid][validity]. + Translate a [derivation] into a [store derivation]. - This means either running the `builder` executable as specified in the corresponding [derivation] or fetching a pre-built [store object] from a [substituter]. + See [`nix-instantiate`](./command-ref/nix-instantiate.md). - See [`nix-build`](./command-ref/nix-build.md) and [`nix-store --realise`](./command-ref/nix-store.md#operation---realise). + [instantiate]: #gloss-instantiate - See [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental). +- [realise]{#gloss-realise}, realisation - [realise]: #gloss-realise + Ensure a [store path] is [valid][validity]. - - [content-addressed derivation]{#gloss-content-addressed-derivation}\ - A derivation which has the - [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed) - attribute set to `true`. + This means either running the [`builder`](@docroot@/language/derivations.md#attr-builder) executable as specified in the corresponding [derivation], or fetching a pre-built [store object] from a [substituter], or delegating to a [remote builder](@docroot@/advanced-topics/distributed-builds.html) and retrieving the outputs. <!-- TODO: link [running] to build process page, #8888 --> - - [fixed-output derivation]{#gloss-fixed-output-derivation}\ - A derivation which includes the - [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute. + See [`nix-build`](./command-ref/nix-build.md) and [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md). - - [store]{#gloss-store}\ - The location in the file system where store objects live. Typically - `/nix/store`. + See [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental). - From the perspective of the location where Nix is - invoked, the Nix store can be referred to - as a "_local_" or a "_remote_" one: + [realise]: #gloss-realise - + A *local store* exists on the filesystem of - the machine where Nix is invoked. You can use other - local stores by passing the `--store` flag to the - `nix` command. Local stores can be used for building derivations. +- [content-addressed derivation]{#gloss-content-addressed-derivation} - + A *remote store* exists anywhere other than the - local filesystem. One example is the `/nix/store` - directory on another machine, accessed via `ssh` or - served by the `nix-serve` Perl script. + A derivation which has the + [`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed) + attribute set to `true`. - [store]: #gloss-store +- [fixed-output derivation]{#gloss-fixed-output-derivation} - - [chroot store]{#gloss-chroot-store}\ - A local store whose canonical path is anything other than `/nix/store`. + A derivation which includes the + [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute. - - [binary cache]{#gloss-binary-cache}\ - A *binary cache* is a Nix store which uses a different format: its - metadata and signatures are kept in `.narinfo` files rather than in a - Nix database. This different format simplifies serving store objects - over the network, but cannot host builds. Examples of binary caches - include S3 buckets and the [NixOS binary - cache](https://cache.nixos.org). +- [store]{#gloss-store} - - [store path]{#gloss-store-path}\ - The location of a [store object] in the file system, i.e., an - immediate child of the Nix store directory. + The location in the file system where store objects live. Typically + `/nix/store`. - Example: `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1` + From the perspective of the location where Nix is + invoked, the Nix store can be referred to + as a "_local_" or a "_remote_" one: - [store path]: #gloss-store-path + + A [local store]{#gloss-local-store} exists on the filesystem of + the machine where Nix is invoked. You can use other + local stores by passing the `--store` flag to the + `nix` command. Local stores can be used for building derivations. - - [store object]{#gloss-store-object}\ - A file that is an immediate child of the Nix store directory. These - can be regular files, but also entire directory trees. Store objects - can be sources (objects copied from outside of the store), - derivation outputs (objects produced by running a build task), or - derivations (files describing a build task). + + A *remote store* exists anywhere other than the + local filesystem. One example is the `/nix/store` + directory on another machine, accessed via `ssh` or + served by the `nix-serve` Perl script. - [store object]: #gloss-store-object + [store]: #gloss-store + [local store]: #gloss-local-store - - [input-addressed store object]{#gloss-input-addressed-store-object}\ - A store object produced by building a - non-[content-addressed](#gloss-content-addressed-derivation), - non-[fixed-output](#gloss-fixed-output-derivation) - derivation. +- [chroot store]{#gloss-chroot-store} - - [output-addressed store object]{#gloss-output-addressed-store-object}\ - A store object whose store path hashes its content. This - includes derivations, the outputs of - [content-addressed derivations](#gloss-content-addressed-derivation), - and the outputs of - [fixed-output derivations](#gloss-fixed-output-derivation). + A [local store] whose canonical path is anything other than `/nix/store`. - - [substitute]{#gloss-substitute}\ - A substitute is a command invocation stored in the Nix database that - describes how to build a store object, bypassing the normal build - mechanism (i.e., derivations). Typically, the substitute builds the - store object by downloading a pre-built version of the store object - from some server. +- [binary cache]{#gloss-binary-cache} - - [substituter]{#gloss-substituter}\ - A *substituter* is an additional store from which Nix will - copy store objects it doesn't have. For details, see the - [`substituters` option](./command-ref/conf-file.md#conf-substituters). + A *binary cache* is a Nix store which uses a different format: its + metadata and signatures are kept in `.narinfo` files rather than in a + [Nix database]. This different format simplifies serving store objects + over the network, but cannot host builds. Examples of binary caches + include S3 buckets and the [NixOS binary cache](https://cache.nixos.org). - [substituter]: #gloss-substituter +- [store path]{#gloss-store-path} - - [purity]{#gloss-purity}\ - The assumption that equal Nix derivations when run always produce - the same output. This cannot be guaranteed in general (e.g., a - builder can rely on external inputs such as the network or the - system time) but the Nix model assumes it. + The location of a [store object] in the file system, i.e., an + immediate child of the Nix store directory. - - [Nix expression]{#gloss-nix-expression}\ - A high-level description of software packages and compositions - thereof. Deploying software using Nix entails writing Nix - expressions for your packages. Nix expressions are translated to - derivations that are stored in the Nix store. These derivations can - then be built. - - - [reference]{#gloss-reference}\ - A [store object] `O` is said to have a *reference* to a store object `P` if a [store path] to `P` appears in the contents of `O`. - - Store objects can refer to both other store objects and themselves. - References from a store object to itself are called *self-references*. - References other than a self-reference must not form a cycle. - - [reference]: #gloss-reference - - - [reachable]{#gloss-reachable}\ - A store path `Q` is reachable from another store path `P` if `Q` - is in the *closure* of the *references* relation. - - - [closure]{#gloss-closure}\ - The closure of a store path is the set of store paths that are - directly or indirectly “reachable” from that store path; that is, - it’s the closure of the path under the *references* relation. For - a package, the closure of its derivation is equivalent to the - build-time dependencies, while the closure of its output path is - equivalent to its runtime dependencies. For correct deployment it - is necessary to deploy whole closures, since otherwise at runtime - files could be missing. The command `nix-store -qR` prints out - closures of store paths. - - As an example, if the [store object] at path `P` contains a [reference] - to a store object at path `Q`, then `Q` is in the closure of `P`. Further, if `Q` - references `R` then `R` is also in the closure of `P`. - - [closure]: #gloss-closure + Example: `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1` - - [output path]{#gloss-output-path}\ - A [store path] produced by a [derivation]. - - [output path]: #gloss-output-path - - - [deriver]{#gloss-deriver}\ - The [store derivation] that produced an [output path]. - - - [validity]{#gloss-validity}\ - A store path is valid if all [store object]s in its [closure] can be read from the [store]. + [store path]: #gloss-store-path - For a local store, this means: - - The store path leads to an existing [store object] in that [store]. - - The store path is listed in the Nix database as being valid. - - All paths in the store path's [closure] are valid. +- [file system object]{#gloss-store-object} - [validity]: #gloss-validity - - - [user environment]{#gloss-user-env}\ - An automatically generated store object that consists of a set of - symlinks to “active” applications, i.e., other store paths. These - are generated automatically by - [`nix-env`](./command-ref/nix-env.md). See *profiles*. - - - [profile]{#gloss-profile}\ - A symlink to the current *user environment* of a user, e.g., - `/nix/var/nix/profiles/default`. + The Nix data model for representing simplified file system data. - - [installable]{#gloss-installable}\ - Something that can be realised in the Nix store. - - See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details. - - - [NAR]{#gloss-nar}\ - A *N*ix *AR*chive. This is a serialisation of a path in the Nix - store. It can contain regular files, directories and symbolic - links. NARs are generated and unpacked using `nix-store --dump` - and `nix-store --restore`. + See [File System Object](@docroot@/architecture/file-system-object.md) for details. - - [`∅`]{#gloss-emtpy-set}\ - The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile. + [file system object]: #gloss-file-system-object - - [`ε`]{#gloss-epsilon}\ - The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute. +- [store object]{#gloss-store-object} - - [string interpolation]{#gloss-string-interpolation}\ - Expanding expressions enclosed in `${ }` within a [string], [path], or [attribute name]. - See [String interpolation](./language/string-interpolation.md) for details. + A store object consists of a [file system object], [reference]s to other store objects, and other metadata. + It can be referred to by a [store path]. - [string]: ./language/values.md#type-string - [path]: ./language/values.md#type-path - [attribute name]: ./language/values.md#attribute-set + [store object]: #gloss-store-object + +- [input-addressed store object]{#gloss-input-addressed-store-object} + + A store object produced by building a + non-[content-addressed](#gloss-content-addressed-derivation), + non-[fixed-output](#gloss-fixed-output-derivation) + derivation. + +- [output-addressed store object]{#gloss-output-addressed-store-object} + + A [store object] whose [store path] is determined by its contents. + This includes derivations, the outputs of [content-addressed derivations](#gloss-content-addressed-derivation), and the outputs of [fixed-output derivations](#gloss-fixed-output-derivation). + +- [substitute]{#gloss-substitute} + + A substitute is a command invocation stored in the [Nix database] that + describes how to build a store object, bypassing the normal build + mechanism (i.e., derivations). Typically, the substitute builds the + store object by downloading a pre-built version of the store object + from some server. + +- [substituter]{#gloss-substituter} + + An additional [store]{#gloss-store} from which Nix can obtain store objects instead of building them. + Often the substituter is a [binary cache](#gloss-binary-cache), but any store can serve as substituter. + + See the [`substituters` configuration option](./command-ref/conf-file.md#conf-substituters) for details. + + [substituter]: #gloss-substituter + +- [purity]{#gloss-purity} + + The assumption that equal Nix derivations when run always produce + the same output. This cannot be guaranteed in general (e.g., a + builder can rely on external inputs such as the network or the + system time) but the Nix model assumes it. + +- [Nix database]{#gloss-nix-database} + + An SQlite database to track [reference]s between [store object]s. + This is an implementation detail of the [local store]. + + Default location: `/nix/var/nix/db`. + + [Nix database]: #gloss-nix-database + +- [Nix expression]{#gloss-nix-expression} + + A high-level description of software packages and compositions + thereof. Deploying software using Nix entails writing Nix + expressions for your packages. Nix expressions are translated to + derivations that are stored in the Nix store. These derivations can + then be built. + +- [reference]{#gloss-reference} + + A [store object] `O` is said to have a *reference* to a store object `P` if a [store path] to `P` appears in the contents of `O`. + + Store objects can refer to both other store objects and themselves. + References from a store object to itself are called *self-references*. + References other than a self-reference must not form a cycle. + + [reference]: #gloss-reference + +- [reachable]{#gloss-reachable} + + A store path `Q` is reachable from another store path `P` if `Q` + is in the *closure* of the *references* relation. + +- [closure]{#gloss-closure} + + The closure of a store path is the set of store paths that are + directly or indirectly “reachable” from that store path; that is, + it’s the closure of the path under the *references* relation. For + a package, the closure of its derivation is equivalent to the + build-time dependencies, while the closure of its output path is + equivalent to its runtime dependencies. For correct deployment it + is necessary to deploy whole closures, since otherwise at runtime + files could be missing. The command `nix-store --query --requisites ` prints out + closures of store paths. + + As an example, if the [store object] at path `P` contains a [reference] + to a store object at path `Q`, then `Q` is in the closure of `P`. Further, if `Q` + references `R` then `R` is also in the closure of `P`. + + [closure]: #gloss-closure + +- [output]{#gloss-output} + + A [store object] produced by a [derivation]. + + [output]: #gloss-output + +- [output path]{#gloss-output-path} + + The [store path] to the [output] of a [derivation]. + + [output path]: #gloss-output-path + +- [deriver]{#gloss-deriver} + + The [store derivation] that produced an [output path]. + +- [validity]{#gloss-validity} + + A store path is valid if all [store object]s in its [closure] can be read from the [store]. + + For a [local store], this means: + - The store path leads to an existing [store object] in that [store]. + - The store path is listed in the [Nix database] as being valid. + - All paths in the store path's [closure] are valid. + + [validity]: #gloss-validity + +- [user environment]{#gloss-user-env} + + An automatically generated store object that consists of a set of + symlinks to “active” applications, i.e., other store paths. These + are generated automatically by + [`nix-env`](./command-ref/nix-env.md). See *profiles*. + +- [profile]{#gloss-profile} + + A symlink to the current *user environment* of a user, e.g., + `/nix/var/nix/profiles/default`. + +- [installable]{#gloss-installable} + + Something that can be realised in the Nix store. + + See [installables](./command-ref/new-cli/nix.md#installables) for [`nix` commands](./command-ref/new-cli/nix.md) (experimental) for details. + +- [NAR]{#gloss-nar} + + A *N*ix *AR*chive. This is a serialisation of a path in the Nix + store. It can contain regular files, directories and symbolic + links. NARs are generated and unpacked using `nix-store --dump` + and `nix-store --restore`. + +- [`∅`]{#gloss-emtpy-set} + + The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile. + +- [`ε`]{#gloss-epsilon} + + The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute. + +- [string interpolation]{#gloss-string-interpolation} + + Expanding expressions enclosed in `${ }` within a [string], [path], or [attribute name]. + + See [String interpolation](./language/string-interpolation.md) for details. + + [string]: ./language/values.md#type-string + [path]: ./language/values.md#type-path + [attribute name]: ./language/values.md#attribute-set + +- [experimental feature]{#gloss-experimental-feature} + + Not yet stabilized functionality guarded by named experimental feature flags. + These flags are enabled or disabled with the [`experimental-features`](./command-ref/conf-file.html#conf-experimental-features) setting. + + See the contribution guide on the [purpose and lifecycle of experimental feaures](@docroot@/contributing/experimental-features.md). |