forked from lix-project/lix
103 lines
4.2 KiB
Markdown
103 lines
4.2 KiB
Markdown
|
# Glossary
|
|||
|
|
|
|||
|
|
- derivation
|
|||
|
|
A description of a build action. The result of a derivation is a
|
|||
|
|
store object. Derivations are typically specified in Nix expressions
|
|||
|
|
using the [`derivation` primitive](#ssec-derivation). These are
|
|||
|
|
translated into low-level *store derivations* (implicitly by
|
|||
|
|
`nix-env` and `nix-build`, or explicitly by `nix-instantiate`).
|
|||
|
|
|
|||
|
|
- store
|
|||
|
|
The location in the file system where store objects live. Typically
|
|||
|
|
`/nix/store`.
|
|||
|
|
|
|||
|
|
- store path
|
|||
|
|
The location in the file system of a store object, i.e., an
|
|||
|
|
immediate child of the Nix store directory.
|
|||
|
|
|
|||
|
|
- 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 action), or
|
|||
|
|
derivations (files describing a build action).
|
|||
|
|
|
|||
|
|
- 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.
|
|||
|
|
|
|||
|
|
- 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 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
|
|||
|
|
A store path `P` is said to have a reference to a store path `Q` if
|
|||
|
|
the store object at `P` contains the path `Q` somewhere. The
|
|||
|
|
*references* of a store path are the set of store paths to which it
|
|||
|
|
has a reference.
|
|||
|
|
|
|||
|
|
A derivation can reference other derivations and sources (but not
|
|||
|
|
output paths), whereas an output path only references other output
|
|||
|
|
paths.
|
|||
|
|
|
|||
|
|
- reachable
|
|||
|
|
A store path `Q` is reachable from another store path `P` if `Q` is
|
|||
|
|
in the [closure](#gloss-closure) of the
|
|||
|
|
[references](#gloss-reference) relation.
|
|||
|
|
|
|||
|
|
- 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](#gloss-reference) 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 path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
|
|||
|
|
references `R` then `R` is also in the closure of `P`.
|
|||
|
|
|
|||
|
|
- output path
|
|||
|
|
A store path produced by a derivation.
|
|||
|
|
|
|||
|
|
- deriver
|
|||
|
|
The deriver of an [output path](#gloss-output-path) is the store
|
|||
|
|
derivation that built it.
|
|||
|
|
|
|||
|
|
- validity
|
|||
|
|
A store path is considered *valid* if it exists in the file system,
|
|||
|
|
is listed in the Nix database as being valid, and if all paths in
|
|||
|
|
its closure are also valid.
|
|||
|
|
|
|||
|
|
- user environment
|
|||
|
|
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`](#sec-nix-env). See
|
|||
|
|
[???](#sec-profiles).
|
|||
|
|
|
|||
|
|
- profile
|
|||
|
|
A symlink to the current [user environment](#gloss-user-env) of a
|
|||
|
|
user, e.g., `/nix/var/nix/profiles/default`.
|
|||
|
|
|
|||
|
|
- 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`.
|