forked from lix-project/lix
234 lines
10 KiB
Markdown
234 lines
10 KiB
Markdown
# 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
|
||
|
||
- [store derivation]{#gloss-store-derivation}\
|
||
A [derivation] represented as a `.drv` file in the [store].
|
||
It has a [store path], like any [store object].
|
||
|
||
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\
|
||
Translate a [derivation] into a [store derivation].
|
||
|
||
See [`nix-instantiate`](./command-ref/nix-instantiate.md).
|
||
|
||
[instantiate]: #gloss-instantiate
|
||
|
||
- [realise]{#gloss-realise}, realisation\
|
||
Ensure a [store path] is [valid][validity].
|
||
|
||
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-build`](./command-ref/nix-build.md) and [`nix-store --realise`](@docroot@/command-ref/nix-store/realise.md).
|
||
|
||
See [`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}\
|
||
A derivation which includes the
|
||
[`outputHash`](./language/advanced-attributes.md#adv-attr-outputHash) attribute.
|
||
|
||
- [store]{#gloss-store}\
|
||
The location in the file system where store objects live. Typically
|
||
`/nix/store`.
|
||
|
||
From the perspective of the location where Nix is
|
||
invoked, the Nix store can be referred to
|
||
as a "_local_" or a "_remote_" one:
|
||
|
||
+ 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.
|
||
|
||
+ 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]: #gloss-store
|
||
[local store]: #gloss-local-store
|
||
|
||
- [chroot store]{#gloss-chroot-store}\
|
||
A [local store] whose canonical path is anything other than `/nix/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`
|
||
|
||
[store path]: #gloss-store-path
|
||
|
||
- [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).
|
||
|
||
[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 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).
|
||
|
||
- [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}\
|
||
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).
|
||
|
||
[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 -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
|
||
|
||
- [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].
|
||
|
||
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).
|