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PM2 CHEATSHEET
Production-ready PM2 commands and patterns for Node.js process management

Category: DevOps · Type: cheatsheet
Official docs: https://pm2.keymetrics.io/

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## What is PM2?

**PM2** (Process Manager 2) is a production-ready process manager for Node.js applications. Keep apps running 24/7 with automatic restarts, load balancing, and zero-downtime deployments.

**⚡ Key Features**
- Process Management & Auto Restart
- Load Balancing & Cluster Mode
- Monitoring & Log Management
- Zero Downtime Deployments

**🎯 Use Cases**
- Production Deployment
- Microservices Management
- Performance Optimization
- Real-time Monitoring

---

## 📥 PM2 - Install & Version

Install PM2 globally and verify installation.

```bash
npm install -g pm2
pm2 -v
```

**When to use**
- First-time PM2 setup
- CI/CD agents
- VPS or production servers

## 🚀 PM2 - Start Application

Start a Node.js application with a custom name.

```bash
pm2 start app.js --name my-app
```

Start with environment variables.

```bash
NODE_ENV=production pm2 start app.js --name my-app
```

## 🔌 PM2 - Start with Port

Run application on a specific port.

```bash
PORT=3000 pm2 start app.js --name my-app
```

## 📊 PM2 - List Processes

View all running processes managed by PM2.

```bash
pm2 list
```

## ℹ️ PM2 - Process Status & Info

Get detailed information about a specific process.

```bash
pm2 show my-app
```

Includes:
- PID
- Memory usage
- Restart count
- Environment variables

## 🛑 PM2 - Stop Application

Stop a running process.

```bash
pm2 stop my-app
```

Stop by process ID.

```bash
pm2 stop 0
```

## 🔄 PM2 - Restart Application

Restart application without downtime (single instance).

```bash
pm2 restart my-app
```

Restart all applications.

```bash
pm2 restart all
```

## ⚡ PM2 - Reload (Zero Downtime)

Reload application with zero downtime (cluster mode).

```bash
pm2 reload my-app
```

**Recommended for**
- Production deployments
- API servers
- User-facing services

## 🗑️ PM2 - Delete Process

Remove application from PM2.

```bash
pm2 delete my-app
```

Delete all processes.

```bash
pm2 delete all
```

## 📄 PM2 - Logs (All Processes)

View combined logs.

```bash
pm2 logs
```

## 📝 PM2 - Logs (Single App)

View logs for a specific app.

```bash
pm2 logs my-app
```

## 🧹 PM2 - Clear Logs

Clear all PM2 logs.

```bash
pm2 flush
```

**Useful when**
- Disk usage increases
- Logs grow too large

## 📈 PM2 - Monitor Resources

Live monitoring dashboard.

```bash
pm2 monit
```

Shows:
- CPU usage
- Memory usage
- Restart count

## 🔀 PM2 - Cluster Mode

Run application in cluster mode using all CPU cores.

```bash
pm2 start app.js -i max --name my-app
```

Run with specific number of instances.

```bash
pm2 start app.js -i 4 --name my-app
```

## 📦 PM2 - Ecosystem File

Generate ecosystem configuration.

```bash
pm2 ecosystem
```

Start using ecosystem file.

```bash
pm2 start ecosystem.config.js
```

## 📋 PM2 - Ecosystem Example

```js
module.exports = {
  apps: [
    {
      name: "my-app",
      script: "app.js",
      instances: "max",
      exec_mode: "cluster",
      env: {
        NODE_ENV: "development"
      },
      env_production: {
        NODE_ENV: "production"
      }
    }
  ]
}
```

## 🌍 PM2 - Start with Environment

Start application using production environment.

```bash
pm2 start ecosystem.config.js --env production
```

## 🔁 PM2 - Auto Restart on Crash

PM2 automatically restarts crashed applications.

To limit restarts:

```bash
pm2 start app.js --max-restarts 5
```

## 💾 PM2 - Save Process List

Save current process list for startup.

```bash
pm2 save
```

## 🚀 PM2 - Startup on Server Boot

Generate startup script.

```bash
pm2 startup
```

Follow the command output and then run:

```bash
pm2 save
```

## 👀 PM2 - Reload on File Change (Dev)

Watch files and restart on change.

```bash
pm2 start app.js --watch
```

**Not recommended for production**

## 🔧 PM2 - Update Environment Variables

Reload app after updating env variables.

```bash
pm2 restart my-app --update-env
```

## 🔄 PM2 - Reset Restart Counter

Reset restart count for an app.

```bash
pm2 reset my-app
```

## ❌ PM2 - Uninstall PM2

Remove PM2 globally.

```bash
npm uninstall -g pm2
```

## ✅ PM2 - Common Production Checklist

- [ ] Use cluster mode
- [ ] Enable startup script
- [ ] Save process list
- [ ] Use ecosystem file
- [ ] Monitor memory usage
- [ ] Rotate logs externally
- [ ] Reload instead of restart

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