Claude Code storage

File Write Operations Failing with Permission Errors

Your application fails when trying to write files to disk, throwing EACCES, EPERM, or permission denied errors. File uploads, log writing, cache storage, or report generation all fail because the application process doesn't have write access to the target directories.

This commonly happens when Claude Code generates code that writes to absolute paths like /tmp, /var, or the project root directory, but the deployment environment (Docker container, cloud function, or restricted server) doesn't allow writes to those locations.

The code works perfectly in local development where you run as an admin user, but breaks immediately in production where the application runs as a restricted service account.

Error Messages You Might See

Error: EACCES: permission denied, open '/var/data/output.pdf' EPERM: operation not permitted, mkdir '/app/uploads' OSError: [Errno 13] Permission denied: '/opt/data/cache' Read-only file system
Error: EACCES: permission denied, open '/var/data/output.pdf'EPERM: operation not permitted, mkdir '/app/uploads'OSError: [Errno 13] Permission denied: '/opt/data/cache'Read-only file system

Common Causes

  • Hardcoded absolute paths — Code writes to /tmp or /var/data which may be read-only in containerized environments
  • Read-only filesystem in serverless — Cloud functions and some container runtimes have read-only root filesystems
  • Docker container running as non-root — The application user inside the container doesn't own the target directory
  • Missing directory creation — Code tries to write a file before creating its parent directory
  • SELinux or AppArmor restrictions — Security modules blocking file writes even when Unix permissions allow them

How to Fix It

  1. Use os.tmpdir() or platform-agnostic paths — Replace hardcoded paths with Node's os.tmpdir() or Python's tempfile.gettempdir()
  2. Create directories before writing — Always call fs.mkdirSync(dir, {recursive: true}) or os.makedirs(dir, exist_ok=True) before file operations
  3. Use /tmp in serverless — In AWS Lambda or similar, /tmp is the only writable directory. Configure your app to use it
  4. Set correct Docker permissions — Add RUN chown -R appuser:appuser /app/data in your Dockerfile for writable directories
  5. Use object storage for production — Replace local file writes with S3, GCS, or Supabase Storage for production deployments

Real developers can help you.

Antriksh Narang Antriksh Narang 5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies. Daniel Vázquez Daniel Vázquez Software Engineer with over 10 years of experience on Startups, Government, big tech industry & consulting. Alvin Voo Alvin Voo I’ve watched the tech landscape evolve over the last decade—from the structured days of Java Server Pages to the current "wild west" of Agentic-driven development. While AI can "vibe" a frontend into existence, I specialize in the architecture that keeps it from collapsing. My expertise lies in the critical backend infrastructure: the parts that must be fast, secure, and scalable. I thrive on high-pressure environments, such as when I had only three weeks to architect and launch an Ethereum redemption system with minimal prior crypto knowledge, turning it into a major revenue stream. What I bring to your project: Forensic Debugging: I don't just "patch" bugs; I use tools like Datadog and Explain Analyzers to map out bottlenecks and resolve root causes—like significantly reducing memory usage by optimizing complex DB joins. Full-Stack Context: Deep experience in Node.js and React, ensuring backends play perfectly with mobile and web teams. Sanity in the Age of AI: I bridge the gap between "best practices" and modern speed, ensuring your project isn't just built fast, but built to last. BurnHavoc BurnHavoc Been around fixing other peoples code for 20 years. hanson1014 hanson1014 Full-stack developer experienced in fixing and deploying AI-generated apps from Lovable, Bolt.new, Cursor, and Replit. I specialize in debugging Supabase integration issues (auth flows, RLS policies, database connections), fixing broken deployments, resolving routing/blank screen problems, and cleaning up messy React/Vite codebases. I also build production apps with the Claude API and have shipped a Mac desktop dev tool (Nexterm from scratch. Based in Hong Kong, fast turnaround. Costea Adrian Costea Adrian Embedded Engineer specilizing in perception systems. Latest project was a adas camera calibration system. Prakash Prajapati Prakash Prajapati I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale. Omar Faruk Omar Faruk As a Product Engineer at Klasio, I contributed to end-to-end product development, focusing on scalability, performance, and user experience. My work spanned building and refining core features, developing dynamic website templates, integrating secure and reliable payment gateways, and optimizing the overall system architecture. I played a key role in creating a scalable and maintainable platform to support educators and learners globally. I'm enthusiastic about embracing new challenges and making meaningful contributions. Tejas Chokhawala Tejas Chokhawala Full-stack engineer with 5 years experience building production web apps using React, Next.js and TypeScript. Focused on performance, clean architecture and shipping fast. Experienced with Supabase/Postgres backends, Stripe billing, and building AI-assisted developer tools. Mehdi Ben Haddou Mehdi Ben Haddou - Founder of Chessigma (1M+ users) & many small projects - ex Founding Engineer @Uplane (YC F25) - ex Software Engineer @Amazon and @Booking.com

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Frequently Asked Questions

Why does file writing work locally but not in production?

Local development typically runs as your user with full permissions. Production environments (Docker, serverless, cloud VMs) run as restricted users with limited filesystem access. Always use platform-appropriate writable directories.

Where can I write files in AWS Lambda?

Only the /tmp directory is writable in Lambda, with a 512MB limit (configurable up to 10GB). For persistent storage, upload to S3 instead of writing locally.

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