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Use the preBuild.bash Script

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Overview

The preBuild.bash script runs before packages install during the container build.

Use it to set up the environment and prepare for package installation. Commands run automatically when you rebuild the container.

The script runs as the container user with passwordless sudo access.

You can install system packages, modify permissions, and configure services. Changes persist across container restarts because they’re baked into the image.

The build context is separate from the project.

The script cannot access files in the /project/ directory during build. Install from external sources like GitHub, PyPI, or URLs instead.

Key Concepts

preBuild.bash

Optional bash script in the project root that runs before package installation. Used for environment setup and system preparation.

Build Order

Container build follows: base image —> preBuild.bash —> package installation —> postBuild.bash —> completed image. The onStart.bash script runs later, each time a container starts from that image.

Build Context

Separate folder containing only the containerfile, package files, and build scripts. Does not include project files, so the script cannot access /project/ during build.

Passwordless Sudo

The script can run commands with sudo without password prompts. Allows system-level changes during the build.

Edit preBuild.bash in the Desktop App

Step One: Open the script editor.

  1. Select Project Tab > Project Container > Scripts
  2. Select preBuild.bash
  3. Select Edit Script

Step Two: Add your commands to the script.

  1. Type or paste your bash commands in the editor
  2. Select Save

Step Three: Rebuild the container to apply changes.

  1. Select Project Tab > Project Container > Start Build

Success: The container rebuilds with your script changes applied.

Edit preBuild.bash Directly

Step One: Open the script file in your project root.

  1. Open preBuild.bash in any text editor

Step Two: Add your commands to the script.

  1. Write bash commands in the file
  2. Save the file

Step Three: Rebuild the container.

  1. Select Project Tab > Project Container > Start Build

Success: The container rebuilds with your script changes applied.

What preBuild.bash Can and Cannot Access

The script CANNOT access the following.

  • Files in the project (anything in /project/)
  • Environment variables defined in variables.env
  • Data files or models in your project

The script CAN access the following.

  • System package managers (apt, yum, etc.)
  • Python package managers (pip, conda)
  • External resources (GitHub, PyPI, URLs with curl/wget)
  • System directories and files being created during the build
  • Build-time environment variables you set in the script itself

Common Mistakes to Avoid

Don’t try to copy files from /project/

This will fail because /project/ doesn’t exist during build:

# This FAILS
cp /project/my-config.yaml /opt/app/

Don’t try to pip install from local project files

This will fail because the files aren’t in the build context:

# This FAILS
pip install /project/my-package/

Don’t reference environment variables from variables.env

These aren’t set during the build:

# This FAILS
echo $MY_CUSTOM_VAR  # Variable from variables.env

Workarounds

Install from external sources instead

Download from GitHub or other external locations:

# Install a Python package from GitHub
pip install git+https://github.com/user/repo.git

Set build-time variables in the script

Define variables you need in the build script itself:

# Set a variable for use in this script
export MY_BUILD_VAR="value"
echo $MY_BUILD_VAR

Use Cases for preBuild.bash

Add apt repositories or signing keys before packages install.

#!/bin/bash
# Add a custom apt repository
sudo add-apt-repository ppa:example/repo
sudo apt-get update

Create directories that will be needed later.

#!/bin/bash
# Create directories for data and models
sudo mkdir -p /opt/data /opt/models
sudo chown workbench:workbench /opt/data /opt/models

Install tools needed for compiling packages.

#!/bin/bash
# Install build essentials
sudo apt-get update
sudo apt-get install -y build-essential cmake

Configure custom package sources or mirrors.

#!/bin/bash
# Add custom pip index
mkdir -p /home/workbench/.pip
echo "[global]" > /home/workbench/.pip/pip.conf
echo "index-url = https://internal-pypi.company.com/simple" >> /home/workbench/.pip/pip.conf

Fix base image issues before package installation.

#!/bin/bash
# Fix locale settings
sudo locale-gen en_US.UTF-8
sudo update-locale LANG=en_US.UTF-8

Best Practices

Use set -e for error handling

Exit immediately if any command fails:

#!/bin/bash
set -e

Add comments to explain complex operations

Document what your script does:

# Add custom repository for latest Python build tools
# Required for building machine learning packages

Use absolute paths for file operations

Avoid issues with working directories:

sudo mkdir -p /opt/myapp
# Not: mkdir -p myapp

Test scripts in isolation when possible

Run commands manually in a container to verify they work before adding to scripts.