# 📊 EC2 Disk Usage Monitoring with Amazon CloudWatch Agent

This guide describes how to manually install and configure the **CloudWatch Agent** on an **Ubuntu EC2 instance** to monitor **disk usage** and set up **email alerts** using CloudWatch Alarms.

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## ✅ Prerequisites

- EC2 instance (Ubuntu)
- IAM role attached to the instance with the following policies:
  - `AmazonSSMManagedInstanceCore`
  - `CloudWatchAgentServerPolicy`
- Sudo privileges on the instance
- Access to AWS CloudWatch and SNS for setting up alerts

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## 🔐 Step 1: Attach IAM Role to EC2

1. Go to **EC2 → Instances → [Your Instance]**
2. Click **Actions → Security → Modify IAM Role**
3. Select a role that has:
   - `AmazonSSMManagedInstanceCore`
   - `CloudWatchAgentServerPolicy`
4. Click **Update IAM Role**

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## 📦 Step 2: Install the CloudWatch Agent

```bash
cd /tmp
wget https://s3.amazonaws.com/amazoncloudwatch-agent/ubuntu/amd64/latest/amazon-cloudwatch-agent.deb
sudo dpkg -i -E ./amazon-cloudwatch-agent.deb

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⚙️ Step 3: Create Agent Config File

Create the config JSON file to monitor disk usage:

sudo nano /opt/aws/amazon-cloudwatch-agent/bin/config.json

Paste the following content:

{
  "metrics": {
    "append_dimensions": {
      "InstanceId": "${aws:InstanceId}"
    },
    "metrics_collected": {
      "disk": {
        "measurement": [
          "used_percent"
        ],
        "metrics_collection_interval": 60,
        "resources": [
          "/"
        ]
      }
    }
  }
}

Save and exit.

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▶️ Step 4: Start CloudWatch Agent

Run the following command to start the agent using the above config:

sudo /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl \
  -a fetch-config -m ec2 \
  -c file:/opt/aws/amazon-cloudwatch-agent/bin/config.json \
  -s

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🧹 Step 5: Clean Up Installer (Optional)

rm /tmp/amazon-cloudwatch-agent.deb

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🔍 Step 6: Verify CloudWatch Metrics

1. Go to CloudWatch → Metrics
2. Navigate to CWAgent namespace
3. Check for the metric: disk_used_percent for your instance
4. Make sure values are being recorded

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🔔 Step 7: Create Storage Alert (Alarm)

1. Go to CloudWatch → Alarms → Create Alarm

2. Choose metric: CWAgent → disk_used_percent

3. Set condition:

   • Threshold: Greater than 70
   • Evaluation period: 1 out of 1 datapoints

4. Set Notification:

   • Choose or create an SNS topic
   • Add your email address and confirm it

5. Name the alarm and click Create Alarm

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✅ Summary

Step	Description
1	Attach IAM role to instance
2	Install CloudWatch Agent
3	Create config file to monitor disk usage
4	Start CloudWatch Agent with config
5	(Optional) Remove installer
6	Check CloudWatch metrics
7	Create alarm to notify on high disk usage

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🛠️ Useful Commands

Check disk usage:

df -h

Restart CloudWatch Agent:

sudo systemctl restart amazon-cloudwatch-agent

Stop Agent:

sudo /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a stop

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📬 Notification Tip

If using SNS for alerts, don’t forget to confirm the email address via the subscription confirmation email from AWS!