Configuration

The pixi.toml is the pixi project configuration file, also known as the project manifest.

A toml file is structured in different tables. This document will explain the usage of the different tables. For more technical documentation check crates.io.

The `project` table#

The minimally required information in the project table is:

[project]
name = "project-name"
channels = ["conda-forge"]
platforms = ["linux-64"]

`name`#

The name of the project.

[project]
name = "project-name"

`channels`#

This is a list that defines the channels used to fetch the packages from. If you want to use channels hosted on anaconda.org you only need to use the name of the channel directly.

[project]
channels = ["conda-forge", "robostack", "bioconda", "nvidia", "pytorch"]

Channels situated on the file system are also supported with absolute file paths:

[project]
channels = ["conda-forge", "file:///home/user/staged-recipes/build_artifacts"]

To access private or public channels on prefix.dev or Quetz use the url including the hostname:

[project]
channels = ["conda-forge", "https://repo.prefix.dev/channel-name"]

`platforms`#

Defines the list of platforms that the project supports. Pixi solves the dependencies for all these platforms and puts them in the lockfile (pixi.lock).

[project]
platforms = ["win-64", "linux-64", "osx-64", "osx-arm64"]

The available platforms are listed here: link

`version` (optional)#

The version of the project. This should be a valid version based on the conda Version Spec. See the version documentation, for an explanation of what is allowed in a Version Spec.

[project]
version = "1.2.3"

`authors` (optional)#

This is a list of authors of the project.

[project]
authors = ["John Doe <j.doe@prefix.dev>", "Marie Curie <mss1867@gmail.com>"]

`description` (optional)#

This should contain a short description of the project.

[project]
description = "A simple description"

`license` (optional)#

The license as a valid SPDX string (e.g. MIT AND Apache-2.0)

[project]
license = "MIT"

`license-file` (optional)#

Relative path to the license file.

[project]
license-file = "LICENSE.md"

`readme` (optional)#

Relative path to the README file.

[project]
readme = "README.md"

`homepage` (optional)#

URL of the project homepage.

[project]
homepage = "https://pixi.sh"

`repository` (optional)#

URL of the project source repository.

[project]
repository = "https://github.com/prefix-dev/pixi"

`documentation` (optional)#

URL of the project documentation.

[project]
documentation = "https://pixi.sh"

The `tasks` table#

Tasks are a way to automate certain custom commands in your project. For example, a lint or format step. Tasks in a pixi project are essentially cross-platform shell commands, with a unified syntax across platforms. For more in-depth information, check the Advanced tasks documentation. Pixi's tasks are run in a pixi environment using pixi run and are executed using the deno_task_shell.

[tasks]
simple = "echo This is a simple task"
cmd = { cmd="echo Same as a simple task but now more verbose"}
depending = { cmd="echo run after simple", depends_on="simple"}
alias = { depends_on=["depending"]}

You can modify this table using pixi task.

Note

Specify different tasks for different platforms using the target table

The `system-requirements` table#

The system requirements are used to define minimal system specifications used during dependency resolution. For example, we can define a unix system with a specific minimal libc version. This will be the minimal system specification for the project. System specifications are directly related to the virtual packages.

Currently, the specified defaults are the same as conda-lock's implementation:

LinuxWindowsOsxOsx-arm64

default system requirements for linux

[system-requirements]
linux = "5.10"
libc = { family="glibc", version="2.17" }

default system requirements for windows

[system-requirements]

default system requirements for osx

[system-requirements]
macos = "10.15"

default system requirements for osx-arm64

[system-requirements]
macos = "11.0"

Only if a project requires a different set should you define them.

For example, when installing environments on old versions of linux. You may encounter the following error:

× The current system has a mismatching virtual package. The project requires '__linux' to be at least version '5.10' but the system has version '4.12.14'

This suggests that the system requirements for the project should be lowered. To fix this, add the following table to your configuration:

[system-requirements]
linux = "4.12.14"

Using Cuda in pixi#

If you want to use cuda in your project you need to add the following to your system-requirements table:

[system-requirements]
cuda = "11" # or any other version of cuda you want to use

This informs the solver that cuda is going to be available, so it can lock it into the lockfile if needed.

The `dependencies` table(s)#

This section defines what dependencies you would like to use for your project.

There are multiple dependencies tables. The default is [dependencies], which are dependencies that are shared across platforms.

Dependencies are defined using a VersionSpec. A VersionSpec combines a Version with an optional operator.

Some examples are:

# Use this exact package version
package0 = "1.2.3"
# Use 1.2.3 up to 1.3.0
package1 = "~=1.2.3"
# Use larger than 1.2 lower and equal to 1.4
package2 = ">1.2,<=1.4"
# Bigger or equal than 1.2.3 or lower not including 1.0.0
package3 = ">=1.2.3|<1.0.0"

Dependencies can also be defined as a mapping where it is using a matchspec:

package0 = { version = ">=1.2.3", channel="conda-forge" }
package1 = { version = ">=1.2.3", build="py34_0" }

Tip

The dependencies can be easily added using the pixi add command line. Running add for an existing dependency will replace it with the newest it can use.

Note

To specify different dependencies for different platforms use the target table

`dependencies`#

Add any conda package dependency that you want to install into the environment. Don't forget to add the channel to the project table should you use anything different than conda-forge. Even if the dependency defines a channel that channel should be added to the project.channels list.

[dependencies]
python = ">3.9,<=3.11"
rust = "1.72"
pytorch-cpu = { version = "~=1.1", channel = "pytorch" }

`pypi-dependencies` (Beta feature)#

Details regarding the PyPI integration

We use uv, which is a new fast pip replacement written in Rust.

We integrate uv as a library, so we use the uv resolver, to which we pass the conda packages as 'locked'. This disallows uv from installing these dependencies itself, and ensures it uses the exact version of these packages in the resolution. This is unique amongst conda based package managers, which usually just call pip from a subprocess.

The uv resolution is included in the lock file directly.

Pixi directly supports depending on PyPI packages, the PyPA calls a distributed package a 'distribution'. There are Source and Binary distributions both of which are supported by pixi. These distributions are installed into the environment after the conda environment has been resolved and installed. PyPI packages are not indexed on prefix.dev but can be viewed on pypi.org.

Important considerations

Stability: PyPI packages might be less stable than their conda counterparts. Prefer using conda packages in the dependencies table where possible.
Compatibility limitations: Currently, pixi doesn't support: - git dependencies (git+https://github.com/package-org/package.git) - Source dependencies - Private PyPI repositories

PEP404 Version specification:#

These dependencies don't follow the conda matchspec specification. The version is a string specification of the version according to PEP404/PyPA. Additionally, a list of extra's can be included, which are essentially optional dependencies. Note that this version is distinct from the conda MatchSpec type. See the example below to see how this is used in practice:

[dependencies]
# When using pypi-dependencies, python is needed to resolve pypi dependencies
# make sure to include this
python = ">=3.6"

[pypi-dependencies]
pytest = "*"  # This means any version (the wildcard `*` is a pixi addition, not part of the specification)
pre-commit = "~=3.5.0" # This is a single version specifier
# Using the toml map allows the user to add `extras`
requests = {version = ">= 2.8.1, ==2.8.*", extras=["security", "tests"]}

Did you know you can use: add --pypi?

Use the --pypi flag with the add command to quickly add PyPI packages from the CLI. E.g pixi add --pypi flask

Source dependencies#

The Source Distribution Format is a source based format (sdist for short), that a package can include alongside the binary wheel format. Because these distributions need to be built, the need a python executable to do this. This is why python needs to be present in a conda environment. Sdists usually depend on system packages to be built, especially when compiling C/C++ based python bindings. Think for example of Python SDL2 bindindings depending on the C library: SDL2. To help built these dependencies we activate the conda environment that includes these pypi dependencies before resolving. This way when a source distribution depends on gcc for example, it's used from the conda environment instead of the system.

`host-dependencies`#

This table contains dependencies that are needed to build your project but which should not be included when your project is installed as part of another project. In other words, these dependencies are available during the build but are no longer available when your project is installed. Dependencies listed in this table are installed for the architecture of the target machine.

[host-dependencies]
python = "~=3.10.3"

Typical examples of host dependencies are:

Base interpreters: a Python package would list python here and an R package would list mro-base or r-base.
Libraries your project links against during compilation like openssl, rapidjson, or xtensor.

`build-dependencies`#

This table contains dependencies that are needed to build the project. Different from dependencies and host-dependencies these packages are installed for the architecture of the build machine. This enables cross-compiling from one machine architecture to another.

[build-dependencies]
cmake = "~=3.24"

Typical examples of build dependencies are:

Compilers are invoked on the build machine, but they generate code for the target machine. If the project is cross-compiled, the architecture of the build and target machine might differ.
cmake is invoked on the build machine to generate additional code- or project-files which are then include in the compilation process.

Info

The build target refers to the machine that will execute the build. Programs and libraries installed by these dependencies will be executed on the build machine.

For example, if you compile on a MacBook with an Apple Silicon chip but target Linux x86_64 then your build platform is osx-arm64 and your host platform is linux-64.

The `activation` table#

If you want to run an activation script inside the environment when either doing a pixi run or pixi shell these can be defined here. The scripts defined in this table will be sourced when the environment is activated using pixi run or pixi shell

Note

The activation scripts are run by the system shell interpreter as they run before an environment is available. This means that it runs as cmd.exe on windows and bash on linux and osx (Unix). Only .sh, .bash and .bat files are supported.

If you have scripts per platform use the target table.

[activation]
scripts = ["env_setup.sh"]
# To support windows platforms as well add the following
[target.win-64.activation]
scripts = ["env_setup.bat"]

The `target` table#

The target table is a table that allows for platform specific configuration. Allowing you to make different sets of tasks or dependencies per platform.

The target table is currently implemented for the following sub-tables:

activation
dependencies
tasks

The target table is defined using [target.PLATFORM.SUB-TABLE]. E.g [target.linux-64.dependencies]

The platform can be any of:

win, osx, linux or unix (unix matches linux and osx)
or any of the (more) specific target platforms, e.g. linux-64, osx-arm64

The sub-table can be any of the specified above.

To make it a bit more clear, let's look at an example below. Currently, pixi combines the top level tables like dependencies with the target-specific ones into a single set. Which, in the case of dependencies, can both add or overwrite dependencies. In the example below, we have cmake being used for all targets but on osx-64 or osx-arm64 a different version of python will be selected.

[dependencies]
cmake = "3.26.4"
python = "3.10"

[target.osx.dependencies]
python = "3.11"

Here are some more examples:

[target.win-64.activation]
scripts = ["setup.bat"]

[target.win-64.dependencies]
msmpi = "~=10.1.1"

[target.win-64.build-dependencies]
vs2022_win-64 = "19.36.32532"

[target.win-64.tasks]
tmp = "echo $TEMP"

[target.osx-64.dependencies]
clang = ">=16.0.6"

The `feature` and `environments` tables#

The feature table allows you to define features that can be used to create different [environments]. The [environments] table allows you to define different environments. The design is explained in the this design document.

Simplest example

[feature.test.dependencies]
pytest = "*"

[environments]
test = ["test"]

This will create an environment called test that has pytest installed.

The `feature` table#

The feature table allows you to define the following fields per feature.

dependencies: Same as the dependencies.
pypi-dependencies: Same as the pypi-dependencies.
system-requirements: Same as the system-requirements.
activation: Same as the activation.
platforms: Same as the platforms. When adding features together the intersection of the platforms is taken. Be aware that the default feature is always implied thus this must contain all platforms the project can support.
channels: Same as the channels. Adding the priority field to the channels to allow concatenation of channels instead of overwriting.
target: Same as the target.
tasks: Same as the tasks.

These tables are all also available without the feature prefix. When those are used we call them the default feature. This is a protected name you can not use for your own feature.

Full feature table specification

[feature.cuda]
activation = {scripts = ["cuda_activation.sh"]}
channels = ["nvidia"] # Results in:  ["nvidia", "conda-forge"] when the default is `conda-forge`
dependencies = {cuda = "x.y.z", cudnn = "12.0"}
pypi-dependencies = {torch = "==1.9.0"}
platforms = ["linux-64", "osx-arm64"]
system-requirements = {cuda = "12"}
tasks = { warmup = "python warmup.py" }
target.osx-arm64 = {dependencies = {mlx = "x.y.z"}}

Full feature table but written as separate tables

[feature.cuda.activation]
scripts = ["cuda_activation.sh"]

[feature.cuda.dependencies]
cuda = "x.y.z"
cudnn = "12.0"

[feature.cuda.pypi-dependencies]
torch = "==1.9.0"

[feature.cuda.system-requirements]
cuda = "12"

[feature.cuda.tasks]
warmup = "python warmup.py"

[feature.cuda.target.osx-arm64.dependencies]
mlx = "x.y.z"

# Channels and Platforms are not available as separate tables as they are implemented as lists
[feature.cuda]
channels = ["nvidia"]
platforms = ["linux-64", "osx-arm64"]

The `environments` table#

The environments table allows you to define environments that are created using the features defined in the feature tables.

Important

default is always implied when creating environments. If you don't want to use the default feature you can keep all the non feature tables empty.

The environments table is defined using the following fields:

features: Vec<Feature>: The features that are included in the environment set, which is also the default field in the environments.
solve-group: String: The solve group is used to group environments together at the solve stage. This is useful for environments that need to have the same dependencies but might extend them with additional dependencies. For instance when testing a production environment with additional test dependencies. These dependencies will then be the same version in all environments that have the same solve group. But the different environments contain different subsets of the solve-groups dependencies set.

Simplest example

[environments]
test = ["test"]

Full environments table specification

[environments]
test = {features = ["test"], solve-group = "test"}
prod = {features = ["prod"], solve-group = "test"}
lint = ["lint"]

Configuration

The project table#

name#

channels#

platforms#

version (optional)#

authors (optional)#

description (optional)#

license (optional)#

license-file (optional)#

readme (optional)#

homepage (optional)#

repository (optional)#

documentation (optional)#

The tasks table#

The system-requirements table#

Using Cuda in pixi#

The dependencies table(s)#

dependencies#

pypi-dependencies (Beta feature)#

PEP404 Version specification:#

Source dependencies#

host-dependencies#

build-dependencies#

The activation table#

The target table#

The feature and environments tables#

The feature table#

The environments table#

The `project` table#

`name`#

`channels`#

`platforms`#

`version` (optional)#

`authors` (optional)#

`description` (optional)#

`license` (optional)#

`license-file` (optional)#

`readme` (optional)#

`homepage` (optional)#

`repository` (optional)#

`documentation` (optional)#

The `tasks` table#

The `system-requirements` table#

The `dependencies` table(s)#

`dependencies`#

`pypi-dependencies` (Beta feature)#

`host-dependencies`#

`build-dependencies`#

The `activation` table#

The `target` table#

The `feature` and `environments` tables#

The `feature` table#

The `environments` table#