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Assuming you followed official guidance to install Nix with Flakes enabled.

Reference in your flake:

inputs = {
composable = {
url = "github:ComposableFi/composable";
inputs.nixpkgs.follows = "nixpkgs";

Shell into dev env:

nix develop --impure

Format all:

nix run ".#fmt"

Check/lint all:

nix run ".#check"

Ask GPT or search internet (or just Github) for any issues and debugging.


Nix is a requirement to set up and start a local development environment with Composable's code. We recommend using the Zero-to-Nix installer. Refer to our docs for how to install and configure Nix.

After configuration, familiarize yourself with the following commands:

nix run "composable#devnet-picasso" to run local devnet for Polkadot CosmWasm development.

nix run "composable#fmt" format all files.

nix build "composable#unit-tests" check unit tests.

Per commit examples

# run Composable node
nix run "github:ComposableFi/composable/<COMMIT>" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed
# run local Picasso DevNet (for CosmWasm development)
nix run "github:ComposableFi/composable/<COMMIT>#devnet-picasso" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed
# CosmWasm on Substrate CLI tool
nix run "github:ComposableFi/composable/<COMMIT>#ccw" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed
# run cross chain devnet with Dotsama and Cosmos nodes 
nix run "github:ComposableFi/composable/<COMMIT>#devnet-xc-fresh" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed
# or same with docker
nix build "github:ComposableFi/composable/<COMMIT>#devnet-xc-image" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed \
&& docker load --input result && docker run -it --entrypoint bash devnet-xc:latest -c /bin/devnet-xc-fresh

Install Nix

Installing Nix

Once you have determined which one you want to use, follow the official Nix installation instructions.

Configuring your Nix install

On NixOS

In your Nix system config (/etc/nixos/configuration.nix by default), configure nix like this:

nix = {
useSandbox = "relaxed";
extraOptions = ''
experimental-features = nix-command flakes
allow-import-from-derivation = true
sandbox = "relaxed";

On non-NixOS

Set the contents of ~/.config/nix/nix.conf to this:

experimental-features = nix-command flakes
sandbox = relaxed
allow-import-from-derivation = true

Append to /etc/nix/nix.conf:

trusted-users = <your user>

Using flags

If you cannot edit these config files, then you can pass the following flags to nix.

--allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed

You are now ready to start running packages!

Running Nix packages

Locations and packages

Before trying to run Nix packages, make sure you have git installed. You can use which git to check for a git installation or run sudo apt install git to install it.

Now you can run Nix packages! In order to run one, you need both a location and a package.


Locations are the source of a git repository containing a Nix flake (such as ours). For example, a location can be:

  • . for your current directory.
  • github:ComposableFi/composable for the latest commit on branch main.
  • github:ComposableFi/composable/67b4df903bf8dc2ab0634f9adf9988203a93af27 for commit 67b4df903bf8dc2ab0634f9adf9988203a93af27.

Note that for the github: locations, you do not need to clone the repository. For . you need to clone the repository and cd into it.


Packages are defined in a repository's flake.nix. For example, a package can be:

  • composable-book which builds this book (so meta!).

If you want to see all packages defined by a repository's flake, run nix flake show "LOCATION", for example: nix flake show "github:ComposableFi/composable".

Once you know which location and package you want, simply run:

nix run "location#package"
nix run "github:ComposableFi/composable#devnet-picasso"

In case of error, append --print-build-logs --show-trace --debug --keep-derivations --keep-outputs to command.

Running in Docker

If you do not have access to nix, but you do have access to docker, then you can run nix packages within docker as follows:

Creating a nix cache volume

In order to save time on subsequent builds, we create a volume that caches nix artifacts:

docker volume create nix

Running your location#package

Make sure you replace location#package with your desired location and package.

docker run -v /var/run/docker.sock:/var/run/docker.sock -v nix:/nix -p 9988:9988 -it nixos/nix bash -c "nix-env -iA nixpkgs.cachix && cachix use composable && nix run location#package --print-build-logs --extra-experimental-features nix-command --extra-experimental-features flakes" --no-sandbox"

Now that you are able to run all packages, let's set up your declarative development environment!