mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-11-15 18:56:16 +02:00
eb7d7780b1
This is needed to avoid this https://github.com/mesonbuild/meson/issues/13774 when we go back to making our subproject directory `src`.
364 lines
15 KiB
Markdown
364 lines
15 KiB
Markdown
# Glossary
|
||
|
||
- [content address]{#gloss-content-address}
|
||
|
||
A
|
||
[*content address*](https://en.wikipedia.org/wiki/Content-addressable_storage)
|
||
is a secure way to reference immutable data.
|
||
The reference is calculated directly from the content of the data being referenced, which means the reference is
|
||
[*tamper proof*](https://en.wikipedia.org/wiki/Tamperproofing)
|
||
--- variations of the data should always calculate to distinct content addresses.
|
||
|
||
For how Nix uses content addresses, see:
|
||
|
||
- [Content-Addressing File System Objects](@docroot@/store/file-system-object/content-address.md)
|
||
- [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md)
|
||
- [content-addressed derivation](#gloss-content-addressed-derivation)
|
||
|
||
Software Heritage's writing on [*Intrinsic and Extrinsic identifiers*](https://www.softwareheritage.org/2020/07/09/intrinsic-vs-extrinsic-identifiers) is also a good introduction to the value of content-addressing over other referencing schemes.
|
||
|
||
Besides content addressing, the Nix store also uses [input addressing](#gloss-input-addressed-store-object).
|
||
|
||
- [derivation]{#gloss-derivation}
|
||
|
||
A description of a build task. The result of a derivation is a
|
||
store object. Derivations declared in Nix expressions are specified
|
||
using the [`derivation` primitive](./language/derivations.md). These are
|
||
translated into low-level *store derivations* (implicitly by
|
||
`nix-build`, or explicitly by `nix-instantiate`).
|
||
|
||
[derivation]: #gloss-derivation
|
||
|
||
- [store derivation]{#gloss-store-derivation}
|
||
|
||
A [derivation] represented as a `.drv` file in the [store].
|
||
It has a [store path], like any [store object].
|
||
It is the [instantiated][instantiate] form of a derivation.
|
||
|
||
Example: `/nix/store/g946hcz4c8mdvq2g8vxx42z51qb71rvp-git-2.38.1.drv`
|
||
|
||
See [`nix derivation show`](./command-ref/new-cli/nix3-derivation-show.md) (experimental) for displaying the contents of store derivations.
|
||
|
||
[store derivation]: #gloss-store-derivation
|
||
|
||
- [instantiate]{#gloss-instantiate}, instantiation
|
||
|
||
Save an evaluated [derivation] as a [store derivation] in the Nix [store].
|
||
|
||
See [`nix-instantiate`](./command-ref/nix-instantiate.md), which produces a store derivation from a Nix expression that evaluates to a derivation.
|
||
|
||
[instantiate]: #gloss-instantiate
|
||
|
||
- [realise]{#gloss-realise}, realisation
|
||
|
||
Ensure a [store path] is [valid][validity].
|
||
|
||
This can be achieved by:
|
||
- Fetching a pre-built [store object] from a [substituter]
|
||
- Running the [`builder`](@docroot@/language/derivations.md#attr-builder) executable as specified in the corresponding [derivation]
|
||
- Delegating to a [remote machine](@docroot@/command-ref/conf-file.md#conf-builders) and retrieving the outputs
|
||
<!-- TODO: link [running] to build process page, #8888 -->
|
||
|
||
See [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md) for a detailed description of the algorithm.
|
||
|
||
See also [`nix-build`](./command-ref/nix-build.md) and [`nix build`](./command-ref/new-cli/nix3-build.md) (experimental).
|
||
|
||
[realise]: #gloss-realise
|
||
|
||
- [content-addressed derivation]{#gloss-content-addressed-derivation}
|
||
|
||
A derivation which has the
|
||
[`__contentAddressed`](./language/advanced-attributes.md#adv-attr-__contentAddressed)
|
||
attribute set to `true`.
|
||
|
||
- [fixed-output derivation]{#gloss-fixed-output-derivation} (FOD)
|
||
|
||
A [derivation] where a cryptographic hash of the [output] is determined in advance using the [`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute, and where the [`builder`](@docroot@/language/derivations.md#attr-builder) executable has access to the network.
|
||
|
||
- [store]{#gloss-store}
|
||
|
||
A collection of [store objects][store object], with operations to manipulate that collection.
|
||
See [Nix Store](./store/index.md) for details.
|
||
|
||
There are many types of stores, see [Store Types](./store/types/index.md) for details.
|
||
|
||
[store]: #gloss-store
|
||
|
||
- [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 path]{#gloss-store-path}
|
||
|
||
The location of a [store object] in the file system, i.e., an immediate child of the Nix store directory.
|
||
|
||
> **Example**
|
||
>
|
||
> `/nix/store/a040m110amc4h71lds2jmr8qrkj2jhxd-git-2.38.1`
|
||
|
||
See [Store Path](@docroot@/store/store-path.md) for details.
|
||
|
||
[store path]: #gloss-store-path
|
||
|
||
- [file system object]{#gloss-file-system-object}
|
||
|
||
The Nix data model for representing simplified file system data.
|
||
|
||
See [File System Object](@docroot@/store/file-system-object.md) for details.
|
||
|
||
[file system object]: #gloss-file-system-object
|
||
|
||
- [store object]{#gloss-store-object}
|
||
|
||
Part of the contents of a [store].
|
||
|
||
A store object consists of a [file system object], [references][reference] to other store objects, and other metadata.
|
||
It can be referred to by a [store path].
|
||
|
||
See [Store Object](@docroot@/store/store-object.md) for details.
|
||
|
||
[store object]: #gloss-store-object
|
||
|
||
- [IFD]{#gloss-ifd}
|
||
|
||
[Import From Derivation](./language/import-from-derivation.md)
|
||
|
||
- [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.
|
||
|
||
- [content-addressed store object]{#gloss-content-addressed-store-object}
|
||
|
||
A [store object] which is [content-addressed](#gloss-content-address),
|
||
i.e. 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).
|
||
|
||
See [Content-Addressing Store Objects](@docroot@/store/store-object/content-address.md) for details.
|
||
|
||
- [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.
|
||
|
||
- [impure derivation]{#gloss-impure-derivation}
|
||
|
||
[An experimental feature](#@docroot@/development/experimental-features.md#xp-feature-impure-derivations) that allows derivations to be explicitly marked as impure,
|
||
so that they are always rebuilt, and their outputs not reused by subsequent calls to realise them.
|
||
|
||
- [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 syntactically valid use of the [Nix language].
|
||
|
||
> **Example**
|
||
>
|
||
> The contents of a `.nix` file form a Nix expression.
|
||
|
||
Nix expressions specify [derivations][derivation], which are [instantiated][instantiate] into the Nix store as [store derivations][store derivation].
|
||
These derivations can then be [realised][realise] to produce [outputs][output].
|
||
|
||
> **Example**
|
||
>
|
||
> Building and deploying software using Nix entails writing Nix expressions as a high-level description of packages and compositions thereof.
|
||
|
||
- [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].
|
||
See [the `outputs` argument to the `derivation` function](@docroot@/language/derivations.md#attr-outputs) for details.
|
||
|
||
[output]: #gloss-output
|
||
|
||
- [output path]{#gloss-output-path}
|
||
|
||
The [store path] to the [output] of a [derivation].
|
||
|
||
[output path]: #gloss-output-path
|
||
|
||
- [output closure]{#gloss-output-closure}\
|
||
The [closure] of an [output path]. It only contains what is [reachable] from the output.
|
||
|
||
- [deriving path]{#gloss-deriving-path}
|
||
|
||
Deriving paths are a way to refer to [store objects][store object] that ar not yet [realised][realise].
|
||
This is necessary because, in general and particularly for [content-addressed derivations][content-addressed derivation], the [output path] of an [output] is not known in advance.
|
||
There are two forms:
|
||
|
||
- *constant*: just a [store path]
|
||
It can be made [valid][validity] by copying it into the store: from the evaluator, command line interface or another store.
|
||
|
||
- *output*: a pair of a [store path] to a [derivation] and an [output] name.
|
||
|
||
- [deriver]{#gloss-deriver}
|
||
|
||
The [store derivation] that produced an [output path].
|
||
|
||
The deriver for an output path can be queried with the `--deriver` option to
|
||
[`nix-store --query`](@docroot@/command-ref/nix-store/query.md).
|
||
|
||
- [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
|
||
[local store]: @docroot@/store/types/local-store.md
|
||
|
||
- [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.
|
||
|
||
- [Nix Archive (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 [Nix Archive](store/file-system-object/content-address.html#serial-nix-archive) 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.
|
||
|
||
- [`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.
|
||
|
||
- [package]{#package}
|
||
|
||
1. A software package; a collection of files and other data.
|
||
|
||
2. A [package attribute set].
|
||
|
||
- [package attribute set]{#package-attribute-set}
|
||
|
||
An [attribute set](@docroot@/language/types.md#attribute-set) containing the attribute `type = "derivation";` (derivation for historical reasons), as well as other attributes, such as
|
||
- attributes that refer to the files of a [package], typically in the form of [derivation outputs](#output),
|
||
- attributes that declare something about how the package is supposed to be installed or used,
|
||
- other metadata or arbitrary attributes.
|
||
|
||
[package attribute set]: #package-attribute-set
|
||
|
||
- [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/types.md#type-string
|
||
[path]: ./language/types.md#type-path
|
||
[attribute name]: ./language/types.md#attribute-set
|
||
|
||
- [base directory]{#gloss-base-directory}
|
||
|
||
The location from which relative paths are resolved.
|
||
|
||
- For expressions in a file, the base directory is the directory containing that file.
|
||
This is analogous to the directory of a [base URL](https://datatracker.ietf.org/doc/html/rfc1808#section-3.3).
|
||
<!-- which is sufficient for resolving non-empty URLs -->
|
||
|
||
<!--
|
||
The wording here may look awkward, but it's for these reasons:
|
||
* "with --expr": it's a flag, and not an option with an accompanying value
|
||
* "written in": the expression itself must be written as an argument,
|
||
whereas the more natural "passed as an argument" allows an interpretation
|
||
where the expression could be passed by file name.
|
||
-->
|
||
- For expressions written in command line arguments with [`--expr`](@docroot@/command-ref/opt-common.html#opt-expr), the base directory is the current working directory.
|
||
|
||
[base directory]: #gloss-base-directory
|
||
|
||
- [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@/development/experimental-features.md).
|
||
|
||
|
||
[Nix language]: ./language/index.md
|