Release 2.4 (2021-11-01)
This is the first release in more than two years and is the result of more than 2800 commits from 195 contributors since release 2.3.
Highlights
-
Nix's error messages have been improved a lot. For instance, evaluation errors now point out the location of the error:
$ nix build error: undefined variable 'bzip3' at /nix/store/449lv242z0zsgwv95a8124xi11sp419f-source/flake.nix:88:13: 87| [ curl 88| bzip3 xz brotli editline | ^ 89| openssl sqlite
-
The
nix
command has seen a lot of work and is now almost at feature parity with the old command-line interface (thenix-*
commands). It aims to be more modern, consistent and pleasant to use than the old CLI. It is still marked as experimental but its interface should not change much anymore in future releases. -
Flakes are a new format to package Nix-based projects in a more discoverable, composable, consistent and reproducible way. A flake is just a repository or tarball containing a file named
flake.nix
that specifies dependencies on other flakes and returns any Nix assets such as packages, Nixpkgs overlays, NixOS modules or CI tests. The newnix
CLI is primarily based around flakes; for example, a command likenix run nixpkgs#hello
runs thehello
application from thenixpkgs
flake.Flakes are currently marked as experimental. For an introduction, see this blog post. For detailed information about flake syntax and semantics, see the
nix flake
manual page. -
Nix's store can now be content-addressed, meaning that the hash component of a store path is the hash of the path's contents. Previously Nix could only build input-addressed store paths, where the hash is computed from the derivation dependency graph. Content-addressing allows deduplication, early cutoff in build systems, and unprivileged closure copying. This is still an experimental feature.
-
The Nix manual has been converted into Markdown, making it easier to contribute. In addition, every
nix
subcommand now has a manual page, documenting every option. -
A new setting that allows experimental features to be enabled selectively. This allows us to merge unstable features into Nix more quickly and do more frequent releases.
Other features
-
There are many new
nix
subcommands:-
nix develop
is intended to replacenix-shell
. It has a number of new features:-
It automatically sets the output environment variables (such as
$out
) to writable locations (such as./outputs/out
). -
It can store the environment in a profile. This is useful for offline work.
-
It can run specific phases directly. For instance,
nix develop --build
runsbuildPhase
.
- It allows dependencies in the Nix store to be "redirected" to
arbitrary directories using the
--redirect
flag. This is useful if you want to hack on a package and some of its dependencies at the same time.
-
-
nix print-dev-env
prints the environment variables and bash functions defined by a derivation. This is useful for users of other shells than bash (especially with--json
). -
nix shell
was previously namednix run
and is intended to replacenix-shell -p
, but without thestdenv
overhead. It simply starts a shell where some packages have been added to$PATH
. -
nix run
(not to be confused with the old subcommand that has been renamed tonix shell
) runs an "app", a flake output that specifies a command to run, or an eponymous program from a package. For example,nix run nixpkgs#hello
runs thehello
program from thehello
package innixpkgs
. -
nix flake
is the container for flake-related operations, such as creating a new flake, querying the contents of a flake or updating flake lock files. -
nix registry
allows you to query and update the flake registry, which maps identifiers such asnixpkgs
to concrete flake URLs. -
nix profile
is intended to replacenix-env
. Its main advantage is that it keeps track of the provenance of installed packages (e.g. exactly which flake version a package came from). It also has some helpful subcommands:-
nix profile history
shows what packages were added, upgraded or removed between each version of a profile. -
nix profile diff-closures
shows the changes between the closures of each version of a profile. This allows you to discover the addition or removal of dependencies or size changes.
Warning: after a profile has been updated using
nix profile
, it is no longer usable withnix-env
. -
-
nix store diff-closures
shows the differences between the closures of two store paths in terms of the versions and sizes of dependencies in the closures. -
nix store make-content-addressable
rewrites an arbitrary closure to make it content-addressed. Such paths can be copied into other stores without requiring signatures. -
nix bundle
uses thenix-bundle
program to convert a closure into a self-extracting executable. -
Various other replacements for the old CLI, e.g.
nix store gc
,nix store delete
,nix store repair
,nix nar dump-path
,nix store prefetch-file
,nix store prefetch-tarball
,nix key
andnix daemon
.
-
-
Nix now has an evaluation cache for flake outputs. For example, a second invocation of the command
nix run nixpkgs#firefox
will not need to evaluate thefirefox
attribute because it's already in the evaluation cache. This is made possible by the hermetic evaluation model of flakes.Intermediate results are not cached.
-
The new
--offline
flag disables substituters and causes all locally cached tarballs and repositories to be considered up-to-date. -
The new
--refresh
flag causes all locally cached tarballs and repositories to be considered out-of-date. -
Many
nix
subcommands now have a--json
option to produce machine-readable output. -
nix repl
has a new:doc
command to show documentation about builtin functions (e.g.:doc builtins.map
). -
Binary cache stores now have an option
index-debug-info
to create an index of DWARF debuginfo files for use bydwarffs
. -
To support flakes, Nix now has an extensible mechanism for fetching source trees. Currently it has the following backends:
-
Git repositories
-
Mercurial repositories
-
GitHub and GitLab repositories (an optimisation for faster fetching than Git)
-
Tarballs
-
Arbitrary directories
The fetcher infrastructure is exposed via flake input specifications and via the
fetchTree
built-in. -
-
Languages changes: the only new language feature is that you can now have antiquotations in paths, e.g.
./${foo}
instead of./. + foo
. -
New built-in functions:
-
builtins.fetchTree
allows fetching a source tree using any backends supported by the fetcher infrastructure. It subsumes the functionality of existing built-ins likefetchGit
,fetchMercurial
andfetchTarball
. -
builtins.getFlake
fetches a flake and returns its output attributes. This function should not be used inside flakes! Use flake inputs instead. -
builtins.floor
andbuiltins.ceil
round a floating-point number down and up, respectively.
-
-
Experimental support for recursive Nix. This means that Nix derivations can now call Nix to build other derivations. This is not in a stable state yet and not well documented.
-
The new experimental feature
no-url-literals
disables URL literals. This helps to implement RFC 45. -
Nix now uses
libarchive
to decompress and unpack tarballs and zip files, sotar
is no longer required. -
The priority of substituters can now be overridden using the
priority
substituter setting (e.g.--substituters 'http://cache.nixos.org?priority=100 daemon?priority=10'
). -
nix edit
now supports non-derivation attributes, e.g.nix edit .#nixosConfigurations.bla
. -
The
nix
command now provides command line completion forbash
,zsh
andfish
. Since the support for getting completions is built intonix
, it's easy to add support for other shells. -
The new
--log-format
flag selects what Nix's output looks like. It defaults to a terse progress indicator. There is a newinternal-json
output format for use by other programs. -
nix eval
has a new--apply
flag that applies a function to the evaluation result. -
nix eval
has a new--write-to
flag that allows it to write a nested attribute set of string leaves to a corresponding directory tree. -
Memory improvements: many operations that add paths to the store or copy paths between stores now run in constant memory.
-
Many
nix
commands now support the flag--derivation
to operate on a.drv
file itself instead of its outputs. -
There is a new store called
dummy://
that does not support building or adding paths. This is useful if you want to use the Nix evaluator but don't have a Nix store. -
The
ssh-ng://
store now allows substituting paths on the remote, asssh://
already did. -
When auto-calling a function with an ellipsis, all arguments are now passed.
-
New
nix-shell
features:-
It preserves the
PS1
environment variable ifNIX_SHELL_PRESERVE_PROMPT
is set. -
With
-p
, it passes any--arg
s as Nixpkgs arguments. -
Support for structured attributes.
-
-
nix-prefetch-url
has a new--executable
flag. -
On
x86_64
systems,x86_64
microarchitecture levels are mapped to additional system types (e.g.x86_64-v1-linux
). -
The new
--eval-store
flag allows you to use a different store for evaluation than for building or storing the build result. This is primarily useful when you want to query whether something exists in a read-only store, such as a binary cache:# nix path-info --json --store https://cache.nixos.org \ --eval-store auto nixpkgs#hello
(Here
auto
indicates the local store.) -
The Nix daemon has a new low-latency mechanism for copying closures. This is useful when building on remote stores such as
ssh-ng://
. -
Plugins can now register
nix
subcommands. -
The
--indirect
flag tonix-store --add-root
has become a no-op.--add-root
will always generate indirect GC roots from now on.
Incompatible changes
-
The
nix
command is now marked as an experimental feature. This means that you need to addexperimental-features = nix-command
to your
nix.conf
if you want to use it, or pass--extra-experimental-features nix-command
on the command line. -
The
nix
command no longer has a syntax for referring to packages in a channel. This means that the following no longer works:nix build nixpkgs.hello # Nix 2.3
Instead, you can either use the
#
syntax to select a package from a flake, e.g.nix build nixpkgs#hello
Or, if you want to use the
nixpkgs
channel in theNIX_PATH
environment variable:nix build -f '<nixpkgs>' hello
-
The old
nix run
has been renamed tonix shell
, while there is a newnix run
that runs a default command. So instead ofnix run nixpkgs.hello -c hello # Nix 2.3
you should use
nix shell nixpkgs#hello -c hello
or just
nix run nixpkgs#hello
if the command you want to run has the same name as the package.
-
It is now an error to modify the
plugin-files
setting via a command-line flag that appears after the first non-flag argument to any command, including a subcommand tonix
. For example,nix-instantiate default.nix --plugin-files ""
must now becomenix-instantiate --plugin-files "" default.nix
. -
We no longer release source tarballs. If you want to build from source, please build from the tags in the Git repository.
Contributors
This release has contributions from Adam Höse, Albert Safin, Alex Kovar, Alex Zero, Alexander Bantyev, Alexandre Esteves, Alyssa Ross, Anatole Lucet, Anders Kaseorg, Andreas Rammhold, Antoine Eiche, Antoine Martin, Arnout Engelen, Arthur Gautier, aszlig, Ben Burdette, Benjamin Hipple, Bernardo Meurer, Björn Gohla, Bjørn Forsman, Bob van der Linden, Brian Leung, Brian McKenna, Brian Wignall, Bruce Toll, Bryan Richter, Calle Rosenquist, Calvin Loncaric, Carlo Nucera, Carlos D'Agostino, Chaz Schlarp, Christian Höppner, Christian Kampka, Chua Hou, Chuck, Cole Helbling, Daiderd Jordan, Dan Callahan, Dani, Daniel Fitzpatrick, Danila Fedorin, Daniël de Kok, Danny Bautista, DavHau, David McFarland, Dima, Domen Kožar, Dominik Schrempf, Dominique Martinet, dramforever, Dustin DeWeese, edef, Eelco Dolstra, Ellie Hermaszewska, Emilio Karakey, Emily, Eric Culp, Ersin Akinci, Fabian Möller, Farid Zakaria, Federico Pellegrin, Finn Behrens, Florian Franzen, Félix Baylac-Jacqué, Gabriella Gonzalez, Geoff Reedy, Georges Dubus, Graham Christensen, Greg Hale, Greg Price, Gregor Kleen, Gregory Hale, Griffin Smith, Guillaume Bouchard, Harald van Dijk, illustris, Ivan Zvonimir Horvat, Jade, Jake Waksbaum, jakobrs, James Ottaway, Jan Tojnar, Janne Heß, Jaroslavas Pocepko, Jarrett Keifer, Jeremy Schlatter, Joachim Breitner, Joe Pea, John Ericson, Jonathan Ringer, Josef Kemetmüller, Joseph Lucas, Jude Taylor, Julian Stecklina, Julien Tanguy, Jörg Thalheim, Kai Wohlfahrt, keke, Keshav Kini, Kevin Quick, Kevin Stock, Kjetil Orbekk, Krzysztof Gogolewski, kvtb, Lars Mühmel, Leonhard Markert, Lily Ballard, Linus Heckemann, Lorenzo Manacorda, Lucas Desgouilles, Lucas Franceschino, Lucas Hoffmann, Luke Granger-Brown, Madeline Haraj, Marwan Aljubeh, Mat Marini, Mateusz Piotrowski, Matthew Bauer, Matthew Kenigsberg, Mauricio Scheffer, Maximilian Bosch, Michael Adler, Michael Bishop, Michael Fellinger, Michael Forney, Michael Reilly, mlatus, Mykola Orliuk, Nathan van Doorn, Naïm Favier, ng0, Nick Van den Broeck, Nicolas Stig124 Formichella, Niels Egberts, Niklas Hambüchen, Nikola Knezevic, oxalica, p01arst0rm, Pamplemousse, Patrick Hilhorst, Paul Opiyo, Pavol Rusnak, Peter Kolloch, Philipp Bartsch, Philipp Middendorf, Piotr Szubiakowski, Profpatsch, Puck Meerburg, Ricardo M. Correia, Rickard Nilsson, Robert Hensing, Robin Gloster, Rodrigo, Rok Garbas, Ronnie Ebrin, Rovanion Luckey, Ryan Burns, Ryan Mulligan, Ryne Everett, Sam Doshi, Sam Lidder, Samir Talwar, Samuel Dionne-Riel, Sebastian Ullrich, Sergei Trofimovich, Sevan Janiyan, Shao Cheng, Shea Levy, Silvan Mosberger, Stefan Frijters, Stefan Jaax, sternenseemann, Steven Shaw, Stéphan Kochen, SuperSandro2000, Suraj Barkale, Taeer Bar-Yam, Thomas Churchman, Théophane Hufschmitt, Timothy DeHerrera, Timothy Klim, Tobias Möst, Tobias Pflug, Tom Bereknyei, Travis A. Everett, Ujjwal Jain, Vladimír Čunát, Wil Taylor, Will Dietz, Yaroslav Bolyukin, Yestin L. Harrison, YI, Yorick van Pelt, Yuriy Taraday and zimbatm.