06 / 06

Set up your project

Make sure the following prerequisites are in place before you begin:

Set up PostgreSQL database

Rell needs PostgreSQL 16.3. You can use the IDE without a database, but you won't be able to run a node. A console or a remote postchain app doesn't need a database.

Rell expects these database settings by default:

database: postchain
user: postchain
password: postchain

Install

Install Homebrew by following the Homebrew setup instructions.

Install PostgreSQL:

shell

brew install postgresql@16brew services start postgresql@16createuser -s postgres

Create and configure the database:

plsql

psql -U postgres -c "CREATE DATABASE postchain WITH TEMPLATE = template0 LC_COLLATE = 'C.UTF-8' LC_CTYPE = 'C.UTF-8' ENCODING 'UTF-8';" -c "CREATE ROLE postchain LOGIN ENCRYPTED PASSWORD 'postchain'; GRANT ALL ON DATABASE postchain TO postchain;"

Install PostgreSQL:
bash
```
sudo apt install postgresql-16
```

Create and configure the database:

bash

sudo -u postgres psql -c "CREATE DATABASE postchain WITH TEMPLATE = template0 LC_COLLATE = 'C.UTF-8' LC_CTYPE = 'C.UTF-8' ENCODING 'UTF-8';" -c "CREATE ROLE postchain LOGIN ENCRYPTED PASSWORD 'postchain'; GRANT ALL ON DATABASE postchain TO postchain;"

Install Docker by following the Docker setup instructions.
Create and configure the database:
dockerfile
```
docker run --name postgres -e POSTGRES_USER=postchain -e POSTGRES_PASSWORD=postchain -p 5432:5432 -d postgres:16.3-alpine3.20
```
note
The Alpine image of PostgreSQL is used here because its default collation settings are already correct. You can also set the collation explicitly with this environment variable:
bash
```
POSTGRES_INITDB_ARGS="--lc-collate=C.UTF-8 --lc-ctype=C.UTF-8 --encoding=UTF-8"
```

Get the PostgreSQL installer from the PostgreSQL download page.
Run the installer, then add the PostgreSQL folder that holds the binaries to your environment variables. In the Command Prompt (CMD), run the command below. Check that the path points to your binaries and substitute the real version number for the <version> placeholder:
shell
```
setx POSTGRESQL "C:\Program Files\PostgreSQL\<version>\bin"
```
Close and reopen the Command Prompt (CMD) so the new environment variables take effect. Then run these two commands, one after the other, to create and configure the database:
plsql
```
psql -U postgres -c "CREATE DATABASE postchain WITH TEMPLATE = template0 LC_COLLATE = 'en_US.UTF-8' LC_CTYPE = 'en_US.UTF-8' ENCODING 'UTF-8';"psql -U postgres -c "CREATE ROLE postchain LOGIN ENCRYPTED PASSWORD 'postchain'; GRANT ALL ON DATABASE postchain TO postchain;"
```
note
On some Windows versions, you may hit permission errors or problems caused by a faulty PostgreSQL installation. In that case, install Docker and run PostgreSQL as a container instead.

Install Chromia CLI

The steps below show how to install and update the Chromia CLI.

Prerequisite

You need the following before you start:

PostgreSQL database: Follow Set up PostgreSQL database.
RELL_JAVA environment: Chromia CLI runs on a Java runtime, version 21 or later. The package managers handle this for you, so no manual setup is needed. To choose a specific Java runtime for Chromia CLI, set the RELL_JAVA environment variable to the location of a valid Java installation.

Installation

Install Chromia CLI through a package manager, or download it from Chromia CLI Packages.

On macOS, install Chromia CLI (chr) as follows:

If you don't have Homebrew yet, install it:

bash

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

bash

brew tap chromia/core https://gitlab.com/chromaway/core-tools/homebrew-chromia.git

Install Chromia CLI:
bash
```
brew install chromia/core/chr
```
info
To pin a particular Chromia CLI version, run:
shell
```
brew install chromia/core/chr@<version>brew unlink chrbrew link chr@<version>
```
To see which versions are available, run brew search chr.
Confirm the installation by printing the version:
bash
```
chr --version
```

On Linux or WSL (Windows Subsystem for Linux), install Chromia CLI (chr) as follows:

Fetch the public key for Chromia's apt-repo and add it to your trusted keyrings:

bash

curl -fsSL https://apt.chromia.com/chromia.gpg | sudo tee /usr/share/keyrings/chromia.gpg

Add the Chromia repository to your package sources:

bash

echo "deb [arch=amd64 signed-by=/usr/share/keyrings/chromia.gpg] https://apt.chromia.com stable main" | sudo tee /etc/apt/sources.list.d/chromia.list

Refresh your package sources:
bash
```
sudo apt-get update
```
info
If apt.chromia.com was added on your system before Chromia CLI version 0.16.0, run this command so the repository can be updated:
bash
```
sudo apt-get --allow-releaseinfo-change update
```
After the update finishes, install Chromia CLI:
bash
```
sudo apt-get install chr
```
Confirm the installation by printing the version:
bash
```
chr --version
```

On Windows, install Chromia CLI (chr) with Scoop as follows:

If you don't have Scoop yet, open PowerShell as Administrator and run:
powershell
```
iwr -useb get.scoop.sh | iex
```

Add the Chromia bucket to Scoop:

powershell

scoop bucket add chromia https://gitlab.com/chromaway/core-tools/scoop-chromia/

Add the Java bucket to Scoop:
powershell
```
scoop bucket add java
```
Scoop needs this bucket to fetch openjdk21, which chromia-cli depends on during installation.
Install Chromia CLI:
powershell
```
scoop install chr
```
Confirm the installation by printing the version:
powershell
```
chr --version
```

Updating Chromia CLI

Get the newest Chromia CLI from the package registry. If you installed it through a package manager, update it with the command for your platform:

shell

brew updatebrew upgrade chr

shell

sudo apt-get updatesudo apt-get install chr

shell

scoop updatescoop update chr

Docker

With Docker, you can run a self-contained Linux container that already has Chromia CLI installed. You still need the PostgreSQL database set up.

The published images require Docker to be installed and configured on your host. For Windows, Mac, and Linux instructions, see install Docker in the Docker documentation.

Start the Docker container with Chromia CLI pre-installed

To run the latest Chromia CLI, pass the CLI image name and chr to the docker run command:

shell

docker run --rm -v $(pwd):/usr/app registry.gitlab.com/chromaway/core-tools/chromia-cli/chr:<latest version> chr

Windows Command Prompt Users

Windows Command Prompt (cmd) doesn't understand the $(pwd) syntax. Use one of these instead:

PowerShell: $(Get-Location) or $(pwd)
Command Prompt: %CD%

Command Prompt example:

cmd

docker run --rm -v %CD%:/usr/app registry.gitlab.com/chromaway/core-tools/chromia-cli/chr:<latest version> chr

For details on updating or removing the Docker image, see the Docker CLI reference.

bash

#!/bin/bash# Allocate a pseudo-TTY one when run in interactive modeif [ -t 0 ] && [ -t 1 ] ; then TTY="--tty"; else TTY=""; fidocker run \  # Sets the network to host to not need to change the database hostname (linux only)  --network=host \  # Set timezone based on system settings (linux only)  -e TZ=$(cat /etc/timezone) \  # Sets process ownership to current user  --user $(id -u):$(id -g) \  --mount type=bind,source="/etc/passwd",target=/etc/passwd,readonly \  --mount type=bind,source="/etc/group",target=/etc/group,readonly \  # Configures ssh-agent (only needed if chr install is called on non-public repositores)  -e SSH_AUTH_SOCK=$SSH_AUTH_SOCK \  --volume "$SSH_AUTH_SOCK:$SSH_AUTH_SOCK" \  --mount type=bind,source="${HOME}/.ssh",target=${HOME}/.ssh,readonly \  --mount type=bind,source="${HOME}/.config/jgit",target=${HOME}/.config/jgit \  # Mounts current folder into the container (Use `Get-Location` on PowerShell)  --mount type=bind,source="$(pwd)",target=/usr/app \  --interactive ${TTY} \  --rm \  registry.gitlab.com/chromaway/core-tools/chromia-cli/chr:${CHR_VERSION:-latest} chr "$@"

Windows Command Prompt Users

The bash script uses $(pwd), which Windows Command Prompt doesn't support. On Windows:

PowerShell: run the command unchanged; PowerShell also understands $(pwd)
Command Prompt: Change $(pwd) to %CD% in the mount command

Mount line for Command Prompt:

cmd

--mount type=bind,source="%CD%",target=/usr/app \

Start by creating your blockchain app project with the Chromia CLI.

shell

chr create-rell-dapp my_library --template=plain

shell

cd my_library

Running this command creates the core project files and configuration you need.

Then set up the chromia.yml file:

chromia.yml

blockchains:  my_library:    module: library_managementcompile:  rellVersion: 0.14.9database:  schema: schema_my_librarytest:  modules:    - test

Written for this site from Chromia’s public course. Code samples are the course’s own.