Terms and Definitions in Nix Project
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Terms and Definitions
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| Term | Context | Meaning | Related Links |
|---|---|---|---|
| User Environment | Nix | A set of "active" applications. These applications usually exist in the Nix store. A single Nix user may have multiple User Environments. This is an important concept further explored in User Environment. Profiles and generations are closely related. |
Nix Manual - Basic Package Management chapter |
| (User) Profile | Nix | Profiles simplify managing and switching between user environments (and thus, control which applications and system configurations are used). Most generally, a profile is a link to a generation, and there's a profiles (note the s) folder which collects types of profiles together so that they form lists of generations. In standalone Nix (e.g. on a different Linux distro), its primary use is user profiles. In NixOS, there is also the system profile, which manages system-wide configuration (e.g. /etc, the kernel, initrd, systemd). Tools like Home Manager also have their own profile (which would also be per-user). The user's active profile is defined in ~/.nix-profile, and is what all nix-env commands would operate on by default.❯ ls -l ~/.nix-profile
lrwxrwxrwx ... /home/username/.nix-profile ->
/nix/var/nix/profiles/per-user/username/profile
|
Nix Manual: Profiles Nix Pills - The first profile |
| Generation | Nix | A revision of a user environment, newly created every time the system is updated (with old ones being preserved until manually removed). Technically, each generation is simply a link to a specific user environment in the Nix store. This term connotes the cloning and modification of an existing user environment. Nix's environment rollback facilities rely on Generations. The current generation is a user's currently selected user environment, and is generally selected via the active profile (which is just a symlink, normally in /nix/var/nix/profiles/). | Nix Manual: Profiles |
| Derivation | Nix | A Nix expression which describes a build action. High-level derivations (like the ones describing packages in Nixpkgs), get evaluated into low-level derivations (called store derivations — because they wind up in the Nix store). nix-instantiate is the command which translates high-level derivations into low-level ones. nix-store --realise can then check and finish their build for the nix store, producing output path(s). nix-build is a user-friendly wrapper for the previous commands. Derivations are analogous to package definitions in other package managers.
|
Nix Manual: Glossary - Derivation Nix Manual: Derivation |
| Output path | Nix | A store path produced by a derivation. These are generally analogous to built packages, or pieces of them.❯ ls -ld /nix/store/*-firefox-9*/
dr-xr-xr-x ... /nix/store/v4b8...3d0w-firefox-92.0/
|
Nix Manual: Derivation |
rec { }
|
Nix expressions | The { } block contains "mutually recursive" attributes, which means they can refer to each other.
|
Composing the Hello Package |
expression evaluator
|
Nix | The part of the Nix program which reads and evaluates a Nix expression. | Nix Manual: Common Options --arg Nix Manual: Built-in Functions |
stdenv
|
Nix expressions | An attribute which contains things expected in the most basic Unix environment. (e.g. Bash shell, gcc, cp, tar, grep, etc.)
|
all-packages.nix: stdenv =]
|
config.nix or nixpkgs-config.nix
|
NixOS Wiki | A Nix expression retrieved by and applied to the all-packages.nix Nix expression. This file enables an end-user to customize the Nix expressions contained in the community-owned NixPkgs list or to define entirely new Nix expressions to use with Nix commands. This file's path can be overridden by the NIXPKGS_CONFIG environment variable.
|
all-packages.nix: config
|
| attribute path | nix-env takes this if you pass the `-A` flag [1] | an unambiguous identifier for a package | |
| symbolic package name | [2] | This string represents what you commonly think of as a package. There can be multiple packages with the symbolic name "hello". | |
| selector | this term is used in nix-env error messages [3], it seems to be actually a DrvName struct [4] (a derivation name) | see "symbolic package name" | |
| selection path | nix-shell error message [5] | see "attribute path"[6] | |
| derivation name | manual[7], source code [8] | see "symbolic package name" | |
| package name | IRC[9] | see "symbolic package name" | |
| attribute selection path | source[10] | see "attribute path" |