devbox.json Reference

Your devbox configuration is stored in a devbox.json file, located in your project's root directory. This file can be edited directly, or using the devbox CLI.

{
    "packages": [],
    "env": {},
    "shell": {
        "init_hook": "...",
        "scripts": {}
    },
    "include": [],
    "nixpkgs": {
        "commit": "..."
    }
}

Packages

This is a list of Nix packages that should be installed in your Devbox shell and containers. These packages will only be installed and available within your shell, and will have precedence over any packages installed in your local machine. You can search for Nix packages using Nix Package Search.

You can add packages to your devbox.json using devbox add <package_name>, and remove them using devbox rm <package_name>

Pinning a Specific Version of a Package

You can pin a specific version of a package by adding a @ followed by the version number to the end of the package name. For example, to pin the go package to version 1.19, you can run devbox add go@1.19, or add go@1.19 to the packages list in your devbox.json:

{
    "packages": [
        "go@1.19"
    ]
}

Where possible, pinned packages follow semver. For example, if you pin python@3, it will install the latest version of python with major version 3.

To see a list of packages and their available versions, you can run devbox search <pkg>.

Adding Packages from Flakes

You can add packages from flakes by adding a reference to the flake in the packages list in your devbox.json. We currently support installing Flakes from Github and local paths.

{
    "packages": [
        // Add the default package from a github repository
        "github:numtide/flake-utils",
        // Install a specific attribute or package from a Github hosted flake
        "github:nix-community/fenix#stable.toolchain",
        // Install a package from a specific channel of Nixpkgs
        "github:nixos/nixpkgs/21.05#hello",
        // Install a package form a specific commit of Nixpkgs
        "github:nixos/nixpkgs/5233fd2ba76a3accb5aaa999c00509a11fd0793c#hello",
        // Install a package from a local flake. This should point to a directory that contains a flake.nix file.
        "path:../my-flake#my-package"
    ]
}

To learn more about using flakes, see the Using Flakes guide.

Env

This is a a map of key-value pairs that should be set as Environment Variables when activating devbox shell, running a script with devbox run, or starting a service. These variables will only be set in your Devbox shell, and will have precedence over any environment variables set in your local machine or by Devbox Plugins.

For example, you could set variable $FOO to bar by adding the following to your devbox.json:

{
    "env": {
        "FOO": "bar"
    }
}

Currently, you can only set values using string literals, $PWD, and $PATH. Any other values with environment variables will not be expanded when starting your shell.

Shell

The Shell object defines init hooks and scripts that can be run with your shell. Right now two fields are supported: init_hooks, which run a set of commands every time you start a devbox shell, and scripts, which are commands that can be run using devbox run

Init Hook

The init hook is used to run shell commands before the shell finishes setting up. This hook runs after any other ~/.*rc scripts, allowing you to override environment variables or further customize the shell.

The init hook will run every time a new shell is started using devbox shell or devbox run, and is best used for setting up environment variables, aliases, or other quick setup steps needed to configure your environment. For longer running tasks, you should consider using a Script.

This is an example devbox.json that customizes the prompt and prints a welcome message:

{
    "shell": {
        "init_hook": [
            "export PS1='📦 devbox> '",
            "echo 'Welcome! See CONTRIBUTING.md for tips on contributing to devbox.'"
        ]
    }
}

When run, you'll see:

> devbox shell
Installing nix packages. This may take a while...
Starting a devbox shell...
Welcome! See CONTRIBUTING.md for tips on contributing to devbox.
📦 devbox>

Scripts

Scripts are commands that are executed in your Devbox shell using devbox run <script_name>. They can be used to start up background process (like databases or servers), or to run one off commands (like setting up a dev DB, or running your tests).

Scripts can be defined by giving a name, and one or more commands. Single command scripts can be added by providing a name, and a string:

{
    "shell": {
        "scripts": {
            "print_once": "echo \"Hello Once!\""
        }
    }
}

To run multiple commands in a single script, you can pass them as an array:

{
    "shell": {
        "scripts": {
            "print_twice": [
                "echo \"Hello Once!\"",
                "echo \"Hello Twice!\""
            ]
        }
    }
}

Includes

Includes can be used to explicitly add extra configuration or plugins to your Devbox project. Currently this only supports adding our built-in plugins to your project.

You should use this section to activate plugins when you install a package from a Flake that uses a plugin. To ensure that a plugin is activated for your project, add it to the includes section of your devbox.json. For example, to explicitly activate the PHP plugin, you can add the following to your devbox.json:

{
    "includes": [
        "plugin:php-config"
    ]
}

Nixpkgs

The Nixpkg object is used to optionally configure which version of the Nixpkgs repository you want Devbox to use as the default for installing packages. It currently takes a single field, commit, which takes a commit hash for the specific revision of Nixpkgs you want to use.

If a Nixpkg commit is not set, Devbox will automatically add a default commit hash to your devbox.json. To upgrade your packages to the latest available versions in the future, you can replace the default hash with the latest nixpkgs-unstable hash from https://status.nixos.org.

To learn more, consult our guide on setting the Nixpkg commit hash.

Example: A Rust Devbox

An example of a devbox configuration for a Rust project called hello_world might look like the following:

{
    "packages": [
        "rustc",
        "cargo",
        "libiconv"
    ],
    "env": {
        "RUST_BACKTRACE": "1"
    },
    "shell": {
        "init_hook": [
            "source conf/set-environment.sh",
            "rustup default stable",
            "cargo fetch"
        ],
        "scripts": {
            "test": "cargo test -- --show-output",
            "start" : "cargo run",
            "build-docs": "cargo doc"
        }
    }
}

Packages​

Pinning a Specific Version of a Package​

Adding Packages from Flakes​

Env​

Shell​

Init Hook​

Scripts​

Includes​

Nixpkgs​

Example: A Rust Devbox​