expand on the system type in hacking guide

This commit is contained in:
Valentin Gagarin 2023-06-20 14:10:30 +02:00
parent 3763c7bb5e
commit 4944e37ec0
2 changed files with 54 additions and 23 deletions

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@ -7,12 +7,12 @@ AC_PROG_SED
# 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.guess` script:
# https://git.savannah.gnu.org/cgit/config.git/tree/config.guess
# 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.sub` instead:
# https://git.savannah.gnu.org/cgit/config.git/tree/config.sub
# 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])

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@ -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
```console
$ nix build .#packages.aarch64-linux.default
```
for flake-enabled Nix, or
Given such a setup, executing the build only requires selecting the respective output attribute.
For example, to compile for `aarch64-linux`:
```console
$ nix-build --attr packages.aarch64-linux.default
```
for classic Nix.
or for Nix with the [`flakes`] and [`nix-command`] experimental features enabled:
You can use any of the other supported platforms in place of `aarch64-linux`.
```console
$ nix build .#packages.aarch64-linux.default
```
Cross-compiled builds are available for ARMv6 and ARMv7, and Nix on unsupported platforms can be bootstrapped by adding more `crossSystems` in `flake.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>
```
For historic reasons and backward-compatibility, some CPU and OS identifiers are transformed as follows in [`configure.ac`](https://github.com/nixos/nix/blob/master/config/config.sub):
| `config.guess` | Nix |
|----------------------------|---------------------|
| `amd64` | `x86_64` |
| `i*86` | `i686` |
| `arm6` | `arm6l` |
| `arm7` | `arm7l` |
| `linux-gnu*` | `linux` |
| `linux-musl*` | `linux` |
## Compilation environments