02 / 26Beginner

Set up your project

Set up the following prerequisites before you begin:

Set up PostgreSQL database

Rell needs PostgreSQL 16.3. You can use the IDE without a database, but you cannot run a node from it. A console or a remote postchain app runs without a database.

By default, Rell expects these database settings:

database: postchain
user: postchain
password: postchain

Install

Install Homebrew by following the Homebrew installation guide.

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 installation guide.
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 the ones Rell needs. You can also set the collation explicitly with an 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 website.
Run the installer, then add the PostgreSQL binaries folder to your environment variables. In Command Prompt (CMD), run the command below. Check that the path points to your binaries and swap the <version> placeholder for your installed version number:
shell
```
setx POSTGRESQL "C:\Program Files\PostgreSQL\<version>\bin"
```
Close and reopen 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
Some Windows versions produce permission errors or broken PostgreSQL installations. If you run into these, install Docker and run PostgreSQL as a container instead.

Install Chromia CLI

Follow these steps to install and update the Chromia CLI.

Prerequisite

You need the following in place first:

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 dependency 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 path 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:

Install Homebrew if you don't have it yet:

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:

Download Chromia's apt-repo public key 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 you added apt.chromia.com before Chromia CLI version 0.16.0, run this command so the repository update is allowed:
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:

Install Scoop if you don't have it yet. Run this in PowerShell as Administrator:
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

Download the latest Chromia CLI from the packages page. If you installed it with 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 includes the Chromia CLI. 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 newest Chromia CLI, pass the CLI image name and chr to docker run.

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) does not 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 updating or removing the Docker image, see the Docker command line 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

This bash script relies on $(pwd), which Windows Command Prompt does not support. On Windows:

PowerShell: run the command unchanged; PowerShell also understands $(pwd).
Command Prompt: In the mount command, change $(pwd) to %CD%.

Mount line adjusted 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 book-review --template=plain

shell

cd book-review

The command creates the core project files and configuration you need.

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