Why Install Packages Directly in Environments Instead of Hardlinking?

Why Install Packages Directly in Environments Instead of Linking?

In package management, packages are often installed directly in specific environments rather than being linked to a central location. This raises the question of why this approach is followed.

Conda's Use of Hardlinking

Contrary to the assumption that packages are fully installed in each environment, Conda utilizes a method known as hardlinking. Hardlinks create multiple references to a single file in different locations, resulting in space savings. When a package is installed in an environment, Conda typically creates a hardlink to the original package file stored in the central packages directory.

Benefits of Direct Installation

Despite the existence of hardlinks, there are practical reasons for installing packages directly in environments:

• Simplified Management: Direct installation eliminates the need to manage links between the environment and the central package cache. This simplifies the maintenance and updating of environments.
• Enhanced Portability: Packages installed directly in environments are portable along with the environment. This makes it convenient to share and distribute environments that include all their dependencies.
• Performance Benefits: In some cases, direct installation can provide performance benefits by reducing the need to traverse multiple file paths or access external locations.

Space Savings Example

An example provided in the answer illustrates how hardlinking saves space. Viewing environment directories individually may suggest excessive usage, but using du to calculate the actual disk usage reveals that the combined usage of all environments is significantly lower. This is because the hardlinks point to the shared packages directory, which contains the actual installation files.

Conclusion

While Conda caches downloaded packages in a central location, it utilizes hardlinking to optimize space usage and enhance the efficiency and portability of environments. The direct installation of packages in environments provides a practical balance between storage concerns and the ease of management, portability, and performance benefits.

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