Fix Error: EACCES: permission denied, open '/var/log/app/server.log' in Node.js

This error means Node.js does not have file system permissions to read, write, or execute at the specified path. Common causes include running as the wrong user, incorrect file ownership, or restrictive directory permissions. Fix it by adjusting file permissions, running as the correct user, or writing to a permitted directory.

Reading the Stack Trace

Here's what each line means:

• at Object.openSync (node:fs:603:3): The operating system denied Node's attempt to open the file because the process user lacks the necessary permissions.
• at Logger.write (src/utils/logger.js:18:8): Your logger at line 18 tries to write to a log file in a directory the Node process user cannot access.
• at Object.<anonymous> (src/index.js:6:8): The logger is invoked at startup on line 6, so the permission error crashes the app immediately.

Common Causes

const fs = require('fs');
fs.appendFileSync('/var/log/app/server.log', logEntry);
// Process runs as 'node' user, /var/log/app is owned by root

# Dockerfile
USER node
# docker run -v /host/logs:/var/log/app myapp
# /host/logs is owned by root, 'node' user can't write

// umask 0077 means only the owner can read/write newly created files
fs.writeFileSync('/shared/output.txt', data); // Fails for other users

The Fix

Use an environment variable for the log directory so it can be configured to a writable location in each environment. Create the directory if it does not exist. Catch EACCES specifically to provide a helpful error message.

const fs = require('fs');

class Logger {
  write(message) {
    fs.appendFileSync('/var/log/app/server.log', message + '\n');
  }
}

const fs = require('fs');
const path = require('path');

const LOG_DIR = process.env.LOG_DIR || path.join(process.cwd(), 'logs');

class Logger {
  constructor() {
    if (!fs.existsSync(LOG_DIR)) {
      fs.mkdirSync(LOG_DIR, { recursive: true });
    }
    this.logPath = path.join(LOG_DIR, 'server.log');
  }

  write(message) {
    try {
      fs.appendFileSync(this.logPath, message + '\n');
    } catch (err) {
      if (err.code === 'EACCES') {
        console.error(`Permission denied writing to ${this.logPath}. Set LOG_DIR to a writable directory.`);
      }
      throw err;
    }
  }
}

Testing the Fix

const fs = require('fs');
const path = require('path');
const os = require('os');

describe('Logger', () => {
  let Logger, tempDir;

  beforeEach(() => {
    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'logger-test-'));
    process.env.LOG_DIR = tempDir;
    jest.resetModules();
    Logger = require('./logger').Logger;
  });

  afterEach(() => {
    fs.rmSync(tempDir, { recursive: true, force: true });
  });

  it('writes log messages to the configured directory', () => {
    const logger = new Logger();
    logger.write('test message');
    const content = fs.readFileSync(path.join(tempDir, 'server.log'), 'utf8');
    expect(content).toContain('test message');
  });

  it('creates the log directory if it does not exist', () => {
    process.env.LOG_DIR = path.join(tempDir, 'subdir', 'logs');
    jest.resetModules();
    Logger = require('./logger').Logger;
    const logger = new Logger();
    expect(fs.existsSync(process.env.LOG_DIR)).toBe(true);
  });
});

Run your tests:

npm test

Pushing Through CI/CD

git checkout -b fix/nodejs-permission-denied-logger,git add src/utils/logger.js src/utils/__tests__/logger.test.js,git commit -m "fix: use configurable log directory and handle EACCES",git push origin fix/nodejs-permission-denied-logger

Your CI config should look something like this:

name: CI
on:
  pull_request:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm test -- --coverage
      - run: npm run lint

The Full Manual Process: 18 Steps

Here's every step you just went through to fix this one bug:

1. Notice the error alert or see it in your monitoring tool
2. Open the error dashboard and read the stack trace
3. Identify the file and line number from the stack trace
4. Open your IDE and navigate to the file
5. Read the surrounding code to understand context
6. Reproduce the error locally
7. Identify the root cause
8. Write the fix
9. Run the test suite locally
10. Fix any failing tests
11. Write new tests covering the edge case
12. Run the full test suite again
13. Create a new git branch
14. Commit and push your changes
15. Open a pull request
16. Wait for code review
17. Merge and deploy to production
18. Monitor production to confirm the error is resolved

Total time: 30-60 minutes. For one bug.

npm install bugstack-sdk

const { initBugStack } = require('bugstack-sdk')

initBugStack({ apiKey: process.env.BUGSTACK_API_KEY })

Deploying the Fix (Manual Path)

1. Identify which user the Node.js process runs as.
2. Set correct ownership and permissions on the target directory.
3. Use an environment variable for the log directory path.
4. Run tests to verify write access.
5. Open a PR, merge after CI, and verify in staging.

Frequently Asked Questions