How to make cargo use another path to compile instead of /tmp (No space left on device (os error 28))

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05-10-2024

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Escaping the /tmp Trap: How to Configure Cargo to Compile in a Different Location

Cargo, Rust's build system, can sometimes run into a frustrating problem: "No space left on device (os error 28)". This usually happens when your /tmp directory, the default location for Cargo's temporary build files, fills up. This article will guide you through understanding this issue and show you how to configure Cargo to use an alternative location for compilation, freeing you from this pesky error.

Understanding the /tmp Dilemma

Cargo, like many build systems, uses a temporary directory to store intermediate files during compilation. By default, this directory is /tmp. While /tmp is usually large enough, it can become a bottleneck if you are working with large projects, using multiple build systems simultaneously, or if your system has limited disk space.

Here's a simple example of how you might encounter this issue:

// cargo.toml
[package]
name = "my_project"
version = "0.1.0"
edition = "2021"

[dependencies]
serde = "1.0"

// main.rs
fn main() {
    println!("Hello, world!");
}

Running cargo build could result in the following error:

error: could not create temporary file: No space left on device (os error 28)

Changing Cargo's Compilation Path

To avoid this issue, we can tell Cargo to use a different directory for its temporary files. This can be done using the CARGO_TARGET_DIR environment variable.

Here's how to set it:

1. Choose a suitable directory: You can use any directory with enough space. A good option might be a subdirectory within your project folder, ensuring it's outside the target directory used by Cargo. For example:

   mkdir my_project/build
   

2. Set the environment variable: Before running cargo build, you can set CARGO_TARGET_DIR using your shell's environment variable commands.

   For bash/zsh:

   export CARGO_TARGET_DIR="my_project/build"
   cargo build
   

   For powershell:

   $env:CARGO_TARGET_DIR="my_project/build"
   cargo build
   

3. Permanent solution: To avoid setting the variable every time, you can add it to your shell's configuration files (e.g., .bashrc, .zshrc, .profile) or use system-wide environment variable management tools.

Benefits of Choosing a Different Location

• Improved efficiency: By using a dedicated directory for compilation, you separate the build process from the system's general temporary files. This can improve efficiency, especially on systems with limited resources.
• Better control: You can manage the temporary build files more effectively, allowing you to clean up or monitor them as needed.
• Customization: This approach lets you tailor the compilation process to fit your specific needs and project structure.

Alternative Solutions

While using CARGO_TARGET_DIR is the recommended approach, you can also consider these alternatives:

• Increase /tmp space: If you're facing temporary space issues specifically with /tmp, you can try increasing its size. However, this might not be a sustainable solution for long-term use.
• Clean up /tmp regularly: Periodically clearing out /tmp can help prevent it from filling up. You can use commands like tmpwatch to automate this process.

Conclusion

By understanding the root cause of "No space left on device" errors during Cargo compilation and utilizing the CARGO_TARGET_DIR environment variable, you can effectively control the temporary build location and avoid these frustrating issues. This approach allows you to build your Rust projects with greater efficiency, control, and customization.

Remember to choose a suitable directory for your build files, manage your environment variables properly, and consider alternative solutions if needed. Happy Rusting!