How to Fix Permission Denied in Elixir

Few things halt development faster than an unexpected permission denied in Elixir. The good news is this is a well-understood problem with a clear solution. Let's get you back on track.

What Triggers This

A permission error in Elixir typically means the running process cannot read, write, or execute a resource it needs. Common causes include:

• File or directory ownership doesn't match the application user
• Incorrect chmod settings on critical directories like uploads, cache, or logs

The Fix

case File.write("data/output.txt", content) do
  :ok ->
    Logger.info("File written successfully")
    :ok
  {:error, :eacces} ->
    Logger.error("Permission denied writing to data/output.txt. " <>
      "Fix: chmod 775 data/ && chown -R appuser data/")
    {:error, :permission_denied}
  {:error, reason} ->
    Logger.error("File write failed: #{inspect(reason)}")
    {:error, reason}
end

Pattern match on :eacces to handle permission errors specifically in Elixir. Provide clear fix instructions in the log output.

Deployment Checklist

• Verify the application runs as the correct OS user (not root in production)
• Set directory permissions to 755 for read/execute, 775 for directories that need write access
• Use chown -R appuser:appuser /app/data during container builds to assign proper ownership
• Add permission checks to your application startup sequence so failures are immediate and clear

[Bugsly](https://bugsly.dev) flags permission errors in real time across your Elixir deployments, including the exact file path and user context so you can fix access issues before users notice.