Volatile inputs can disappear

Inputs from the network—even if it doesn’t seem like it—are volatile. It’s best to make a build system not rely on remote data.

If it must be the case, then:

1. ensure integrity using cryptographic checksums,
2. keep backups.

Ideally, a fallback location should be available with the backups.

A good example is how the FreeBSD ports work. Port descriptions contain a list of MASTER_SITES, a list of files to be retrieved in DISTFILES, and a distinfo file with cryptographic checksums for each of these files. The FreeBSD infrastructure ensures that a copy of all distfiles are kept available on a mirror network. When building a port, the files will be downloaded from there if the original master site is unreachable.

---

← Documentation index

Documentation home

Introduction

• Definitions
• History
• Buy-in
• Making plans
• Academic publications

Achieve deterministic builds

• SOURCE_DATE_EPOCH
• Deterministic build systems
• Volatile inputs can disappear
• Stable order for inputs
• Value initialization
• Version information
• Timestamps
• Timezones
• Locales
• Archive metadata
• Stable order for outputs
• Randomness
• Build path
• System images
• JVM

Define a build environment

• What's in a build environment?
• Recording the build environment
• Definition strategies
• Proprietary operating systems

Distribute the environment

• Building from source
• Virtual machine drivers
• Formal definition

Comparison protocol

• Cryptographic checksums
• Embedded signatures
• Sharing certifications

Specifications

• SOURCE_DATE_EPOCH
• BUILD_PATH_PREFIX_MAP (WIP)