Why Doesn\'t Conda Use Linking for Package Installation?

Linking Packages vs. Installation: Balancing Efficiency and Accessibility

When installing packages in Python environments, you may have noticed that they are typically installed in specific directories within conda or pip virtual environments. However, conda maintains a cache of all recently downloaded packages. This raises the question of why conda doesn't simply install all packages in a central location and create links to them when installing them in specific environments.

This approach, known as linking, would theoretically save space in the long run. So, why does conda not employ this method?

Conda's Use of Hardlinks

The key to understanding conda's behavior lies in its usage of hardlinks. When installing packages, conda creates hardlinks, which are file system pointers that reference the same underlying data on the disk. This allows multiple environments to access the same package files without duplicating the data.

Assessing Space Savings

While it may appear that environments take up a significant amount of space due to individual directory sizes, examining the real disk usage with the du command reveals a different picture. By correcting for hardlinks, you can see that conda already saves substantial space. However, this space saving is most apparent when considering the size of the shared packages directory (pkgs).

Conclusion

Conda's use of hardlinks effectively leverages available space by minimizing duplication of package data. This approach balances the efficiency of shared storage with the accessibility provided by individual environment directories. It should be noted that conda clean or pip cache purge can be periodically run to remove unused packages and further reduce space usage.

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