Merge branch 'master' into overlayfs-store

configure.ac

@@ -5,7 +5,14 @@ AC_CONFIG_AUX_DIR(config)
 
 AC_PROG_SED
 
-# Construct a Nix system name (like "i686-linux").
+# Construct a Nix system name (like "i686-linux"):
+# https://www.gnu.org/software/autoconf/manual/html_node/Canonicalizing.html#index-AC_005fCANONICAL_005fHOST-1
+# The inital value is produced by the `config/config.guess` script:
+# upstream: https://git.savannah.gnu.org/cgit/config.git/tree/config.guess
+# It has the following form, which is not documented anywhere:
+# <cpu>-<vendor>-<os>[<version>][-<abi>]
+# If `./configure` is passed any of the `--host`, `--build`, `--target` options, the value comes from `config/config.sub` instead:
+# upstream: https://git.savannah.gnu.org/cgit/config.git/tree/config.sub
 AC_CANONICAL_HOST
 AC_MSG_CHECKING([for the canonical Nix system name])
 

doc/manual/redirects.js

@@ -281,7 +281,7 @@ const redirects = {
     "chap-introduction": "introduction.html",
     "ch-basic-package-mgmt": "package-management/basic-package-mgmt.html",
     "ssec-binary-cache-substituter": "package-management/binary-cache-substituter.html",
-    "sec-channels": "package-management/channels.html",
+    "sec-channels": "command-ref/nix-channel.html",
     "ssec-copy-closure": "package-management/copy-closure.html",
     "sec-garbage-collection": "package-management/garbage-collection.html",
     "ssec-gc-roots": "package-management/garbage-collector-roots.html",

doc/manual/src/SUMMARY.md.in

@@ -21,7 +21,6 @@
   - [Profiles](package-management/profiles.md)
   - [Garbage Collection](package-management/garbage-collection.md)
     - [Garbage Collector Roots](package-management/garbage-collector-roots.md)
-  - [Channels](package-management/channels.md)
   - [Sharing Packages Between Machines](package-management/sharing-packages.md)
     - [Serving a Nix store via HTTP](package-management/binary-cache-substituter.md)
     - [Copying Closures via SSH](package-management/copy-closure.md)

doc/manual/src/command-ref/nix-channel.md

@@ -8,36 +8,46 @@
 
 # Description
 
-A Nix channel is a mechanism that allows you to automatically stay
-up-to-date with a set of pre-built Nix expressions. A Nix channel is
-just a URL that points to a place containing a set of Nix expressions.
-
-To see the list of official NixOS channels, visit
-<https://nixos.org/channels>.
+Channels are a mechanism for referencing remote Nix expressions and conveniently retrieving their latest version.
+
+The moving parts of channels are:
+- The official channels listed at <https://nixos.org/channels>
+- The user-specific list of [subscribed channels](#subscribed-channels)
+- The [downloaded channel contents](#channels)
+- The [Nix expression search path](@docroot@/command-ref/conf-file.md#conf-nix-path), set with the [`-I` option](#opt-i) or the [`NIX_PATH` environment variable](#env-NIX_PATH)
+
+> **Note**
+>
+> The state of a subscribed channel is external to the Nix expressions relying on it.
+> This may limit reproducibility.
+>
+> Dependencies on other Nix expressions can be declared explicitly with:
+> - [`fetchurl`](@docroot@/language/builtins.md#builtins-fetchurl), [`fetchTarball`](@docroot@/language/builtins.md#builtins-fetchTarball), or [`fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) in Nix expressions
+> - the [`-I` option](@docroot@/command-ref/opt-common.md#opt-I) in command line invocations
 
 This command has the following operations:
 
   - `--add` *url* \[*name*\]\
-    Adds a channel named *name* with URL *url* to the list of subscribed
-    channels. If *name* is omitted, it defaults to the last component of
-    *url*, with the suffixes `-stable` or `-unstable` removed.
+    Add a channel *name* located at *url* to the list of subscribed channels.
+    If *name* is omitted, default to the last component of *url*, with the suffixes `-stable` or `-unstable` removed.
+
+    > **Note**
+    >
+    > `--add` does not automatically perform an update.
+    > Use `--update` explicitly.
 
     A channel URL must point to a directory containing a file `nixexprs.tar.gz`.
     At the top level, that tarball must contain a single directory with a `default.nix` file that serves as the channel’s entry point.
 
   - `--remove` *name*\
-    Removes the channel named *name* from the list of subscribed
-    channels.
+    Remove the channel *name* from the list of subscribed channels.
 
   - `--list`\
-    Prints the names and URLs of all subscribed channels on standard
-    output.
+    Print the names and URLs of all subscribed channels on standard output.
 
   - `--update` \[*names*…\]\
-    Downloads the Nix expressions of all subscribed channels (or only
-    those included in *names* if specified) and makes them the default
-    for `nix-env` operations (by symlinking them from the directory
-    `~/.nix-defexpr`).
+    Download the Nix expressions of subscribed channels and create a new generation.
+    Update all channels if none is specified, and only those included in *names* otherwise.
 
   - `--list-generations`\
     Prints a list of all the current existing generations for the
@@ -49,13 +59,8 @@ This command has the following operations:
     ```
 
   - `--rollback` \[*generation*\]\
-    Reverts the previous call to `nix-channel
-                    --update`. Optionally, you can specify a specific channel generation
-    number to restore.
-
-Note that `--add` does not automatically perform an update.
-
-The list of subscribed channels is stored in `~/.nix-channels`.
+    Revert channels to the state before the last call to `nix-channel --update`.
+    Optionally, you can specify a specific channel *generation* number to restore.
 
 {{#include ./opt-common.md}}
 
@@ -69,23 +74,33 @@ The list of subscribed channels is stored in `~/.nix-channels`.
 
 # Examples
 
-To subscribe to the Nixpkgs channel and install the GNU Hello package:
+Subscribe to the Nixpkgs channel and run `hello` from the GNU Hello package:
 
 ```console
 $ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --list
+nixpkgs https://nixos.org/channels/nixpkgs
 $ nix-channel --update
-$ nix-env --install --attr nixpkgs.hello
+$ nix-shell -p hello --run hello
+hello
 ```
 
-You can revert channel updates using `--rollback`:
+Revert channel updates using `--rollback`:
 
 ```console
-$ nix-instantiate --eval --expr '(import <nixpkgs> {}).lib.version'
-"14.04.527.0e935f1"
+$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
+"22.11pre296212.530a53dcbc9"
 
 $ nix-channel --rollback
 switching from generation 483 to 482
 
-$ nix-instantiate --eval --expr '(import <nixpkgs> {}).lib.version'
-"14.04.526.dbadfad"
+$ nix-instantiate --eval '<nixpkgs>' --attr lib.version
+"22.11pre281526.d0419badfad"
+```
+
+Remove a channel:
+
+```console
+$ nix-channel --remove nixpkgs
+$ nix-channel --list
 ```

doc/manual/src/contributing/hacking.md

@@ -110,41 +110,72 @@ You can also build Nix for one of the [supported platforms](#platforms).
 
 ## Platforms
 
-As specified in [`flake.nix`], Nix can be built for various platforms:
-
-- `aarch64-linux`
-- `i686-linux`
-- `x86_64-darwin`
-- `x86_64-linux`
+Nix can be built for various platforms, as specified in [`flake.nix`]:
 
 [`flake.nix`]: https://github.com/nixos/nix/blob/master/flake.nix
 
+- `x86_64-linux`
+- `x86_64-darwin`
+- `i686-linux`
+- `aarch64-linux`
+- `aarch64-darwin`
+- `armv6l-linux`
+- `armv7l-linux`
+
 In order to build Nix for a different platform than the one you're currently
-on, you need to have some way for your system Nix to build code for that
-platform. Common solutions include [remote builders] and [binfmt emulation]
+on, you need a way for your current Nix installation to build code for that
+platform. Common solutions include [remote builders] and [binary format emulation]
 (only supported on NixOS).
 
 [remote builders]: ../advanced-topics/distributed-builds.md
 [binfmt emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
 
-These solutions let Nix perform builds as if you're on the native platform, so
-executing the build is as simple as
+Given such a setup, executing the build only requires selecting the respective attribute.
+For example, to compile for `aarch64-linux`:
 
 ```console
-$ nix build .#packages.aarch64-linux.default
+$ nix-build --attr packages.aarch64-linux.default
 ```
 
-for flake-enabled Nix, or
+or for Nix with the [`flakes`] and [`nix-command`] experimental features enabled:
 
 ```console
-$ nix-build --attr packages.aarch64-linux.default
+$ nix build .#packages.aarch64-linux.default
 ```
 
-for classic Nix.
+Cross-compiled builds are available for ARMv6 (`armv6l-linux`) and ARMv7 (`armv7l-linux`).
+Add more [system types](#system-type) to `crossSystems` in `flake.nix` to bootstrap Nix on unsupported platforms.
+
+## System type
+
+Nix uses a string with he following format to identify the *system type* or *platform* it runs on:
+
+```
+<cpu>-<os>[-<abi>]
+```
+
+It is set when Nix is compiled for the given system, and based on the output of [`config.guess`](https://github.com/nixos/nix/blob/master/config/config.guess) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.guess)):
+
+```
+<cpu>-<vendor>-<os>[<version>][-<abi>]
+```
+
+When Nix is built such that `./configure` is passed any of the `--host`, `--build`, `--target` options, the value is based on the output of [`config.sub`](https://github.com/nixos/nix/blob/master/config/config.sub) ([upstream](https://git.savannah.gnu.org/cgit/config.git/tree/config.sub)):
+
+```
+<cpu>-<vendor>[-<kernel>]-<os>
+```
 
-You can use any of the other supported platforms in place of `aarch64-linux`.
+For historic reasons and backward-compatibility, some CPU and OS identifiers are translated from the GNU Autotools naming convention in [`configure.ac`](https://github.com/nixos/nix/blob/master/config/config.sub) as follows:
 
-Cross-compiled builds are available for ARMv6 and ARMv7, and Nix on unsupported platforms can be bootstrapped by adding more `crossSystems` in `flake.nix`.
+| `config.guess`             | Nix                 |
+|----------------------------|---------------------|
+| `amd64`                    | `x86_64`            |
+| `i*86`                     | `i686`              |
+| `arm6`                     | `arm6l`             |
+| `arm7`                     | `arm7l`             |
+| `linux-gnu*`               | `linux`             |
+| `linux-musl*`              | `linux`             |
 
 ## Compilation environments
 

doc/manual/src/language/constructs.md

@@ -92,10 +92,10 @@ In this fragment from `all-packages.nix`,
 ```nix
 graphviz = (import ../tools/graphics/graphviz) {
   inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
-  inherit (xlibs) libXaw;
+  inherit (xorg) libXaw;
 };
 
-xlibs = {
+xorg = {
   libX11 = ...;
   libXaw = ...;
   ...
@@ -109,7 +109,7 @@ libjpg = ...;
 the set used in the function call to the function defined in
 `../tools/graphics/graphviz` inherits a number of variables from the
 surrounding scope (`fetchurl` ... `yacc`), but also inherits `libXaw`
-(the X Athena Widgets) from the `xlibs` (X11 client-side libraries) set.
+(the X Athena Widgets) from the `xorg` set.
 
 Summarizing the fragment
 
@@ -208,30 +208,41 @@ three kinds of patterns:
     ```nix
     { x, y, z, ... } @ args: z + y + x + args.a
     ```
-    
-    Here `args` is bound to the entire argument, which is further
-    matched against the pattern `{ x, y, z,
-            ... }`. `@`-pattern makes mainly sense with an ellipsis(`...`) as
+
+    Here `args` is bound to the argument *as passed*, which is further
+    matched against the pattern `{ x, y, z, ... }`.
+    The `@`-pattern makes mainly sense with an ellipsis(`...`) as
     you can access attribute names as `a`, using `args.a`, which was
     given as an additional attribute to the function.
-    
+
     > **Warning**
-    > 
-    > The `args@` expression is bound to the argument passed to the
-    > function which means that attributes with defaults that aren't
-    > explicitly specified in the function call won't cause an
-    > evaluation error, but won't exist in `args`.
-    > 
+    >
+    > `args@` binds the name `args` to the attribute set that is passed to the function.
+    > In particular, `args` does *not* include any default values specified with `?` in the function's set pattern.
+    >
     > For instance
-    > 
+    >
     > ```nix
     > let
-    >   function = args@{ a ? 23, ... }: args;
+    >   f = args@{ a ? 23, ... }: [ a args ];
     > in
-    >   function {}
-    > ````
-    > 
-    > will evaluate to an empty attribute set.
+    >   f {}
+    > ```
+    >
+    > is equivalent to
+    >
+    > ```nix
+    > let
+    >   f = args @ { ... }: [ (args.a or 23) args ];
+    > in
+    >   f {}
+    > ```
+    >
+    > and both expressions will evaluate to:
+    >
+    > ```nix
+    > [ 23 {} ]
+    > ```
 
 Note that functions do not have names. If you want to give them a name,
 you can bind them to an attribute, e.g.,

doc/manual/src/package-management/basic-package-mgmt.md

@@ -25,7 +25,7 @@ or completely new ones.)
 
 You can manually download the latest version of Nixpkgs from
 <https://github.com/NixOS/nixpkgs>. However, it’s much more
-convenient to use the Nixpkgs [*channel*](channels.md), since it makes
+convenient to use the Nixpkgs [*channel*](../command-ref/nix-channel.md), since it makes
 it easy to stay up to date with new versions of Nixpkgs. Nixpkgs is
 automatically added to your list of “subscribed” channels when you
 install Nix. If this is not the case for some reason, you can add it