Why Install Packages Instead of Linking in Package Management?

Dependency Management: Why Packages Are Installed Instead of Linked

Package management tools like conda and pip install packages within specific environments rather than linking to a central location. Why is this the preferred approach?

Hardlinking: A Space-Saving Strategy

Conda, in fact, employs hardlinking to conserve space. Hardlinks create multiple references to the same file, reducing disk usage. When packages are installed, hardlinks are created from the central package cache to the specific environment directories.

Measuring Disk Occupancy

To accurately gauge the actual disk space consumed, use du. By examining the size of environment directories individually, the calculated usage may overestimate the true occupancy. By accounting for hardlinks, we obtain a more precise measure.

Example:

$ for d in envs/*; do du -sh $d; done

This command calculates the uncorrected per-environment usage, which appears to indicate significant space consumption.

However, considering the hardlinks, we discover substantial space savings:

$ du -sh envs/*

Separate Installation and Linking

Separating package installation and hardlinking offers several benefits:

• Environment Isolation: Packages are installed and isolated within specific environments, preventing conflicts with other environments.
• Package Upgrades: Upgrading packages in one environment does not affect other environments that reference the same package through hardlinks.
• Cache Optimization: By maintaining a separate package cache, conda can efficiently manage and optimize package downloads, saving time and reducing network traffic.

Conclusion

Installing packages rather than linking provides a robust and space-efficient mechanism for dependency management in Python environments. By leveraging hardlinks, conda minimizes storage requirements while upholding environment isolation and package upgrade flexibility.

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