Name

       nix registry - manage the flake registry

Synopsis

       nix registry [option…] subcommand

       where subcommand is one of the following:

       • nix registry add - add/replace flake in user flake registry
       • nix registry list - list available Nix flakes
       • nix  registry  pin  -  pin a flake to its current version or to the current version of a
         flake URL
       • nix registry remove - remove flake from user flake registry

Description

       nix registry provides subcommands for managing flake registries. Flake  registries  are  a
       convenience  feature that allows you to refer to flakes using symbolic identifiers such as
       nixpkgs, rather than full URLs such as git://github.com/NixOS/nixpkgs. You can  use  these
       identifiers on the command line (e.g. when you do nix run nixpkgs#hello) or in flake input
       specifications in flake.nix files. The latter are automatically resolved to full URLs  and
       recorded in the flake’s flake.lock file.

       In  addition,  the  flake registry allows you to redirect arbitrary flake references (e.g.
       github:NixOS/patchelf) to another location, such as a local fork.

       There are multiple registries. These are, in order from lowest to highest precedence:

       • The global registry, which is a file downloaded from the URL specified  by  the  setting
         flake-registry.  It  is  cached  locally  and updated automatically when it’s older than
         tarball-ttl seconds. The default global registry is kept in a GitHub repository.

       • The  system  registry,  which  is  shared  by  all  users.  The  default   location   is
         /etc/nix/registry.json.  On  NixOS, the system registry can be specified using the NixOS
         option nix.registry.

       • The user registry ~/.config/nix/registry.json. This registry can be modified by commands
         such as nix registry pin.

       • Overrides specified on the command line using the option --override-flake.

Registry format

       A registry is a JSON file with the following format:

       {
         "version": 2,
         "flakes": [
           {
             "from": {
               "type": "indirect",
               "id": "nixpkgs"
             },
             "to": {
               "type": "github",
               "owner": "NixOS",
               "repo": "nixpkgs"
             }
           },
           ...
         ]
       }

       That  is, it contains a list of objects with attributes from and to, both of which contain
       a flake reference in attribute representation. (For example,  {"type":  "indirect",  "id":
       "nixpkgs"}  is  the attribute representation of nixpkgs, while {"type": "github", "owner":
       "NixOS", "repo": "nixpkgs"} is the attribute representation of github:NixOS/nixpkgs.)

       Given some flake reference R, a registry entry is used if its from flake reference matches
       R. R is then replaced by the unification of the to flake reference with R.

Matching

       The  from  flake  reference  in  a  registry  entry  matches some flake reference R if the
       attributes in from are the same as the attributes in R. For example:

       • nixpkgs matches with nixpkgs.

       • nixpkgs matches with nixpkgs/nixos-20.09.

       • nixpkgs/nixos-20.09 does not match with nixpkgs.

       • nixpkgs does not match with git://github.com/NixOS/patchelf.

Unification

       The to flake reference in a registry entry is unified  with  some  flake  reference  R  by
       taking to and applying the rev and ref attributes from R, if specified. For example:

       • github:NixOS/nixpkgs unified with nixpkgs produces github:NixOS/nixpkgs.

       • github:NixOS/nixpkgs        unified        with       nixpkgs/nixos-20.09       produces
         github:NixOS/nixpkgs/nixos-20.09.

       • github:NixOS/nixpkgs/master     unified      with      nixpkgs/nixos-20.09      produces
         github:NixOS/nixpkgs/nixos-20.09.

                                                                                 nix3-registry(1)