Fix CentOS Disk Space Issues Instantly by Expanding AWS EBS Volume (Live Case Study)

Fix CentOS Disk Space Issues Instantly by Expanding AWS EBS Volume (Live Case Study)

Running out of disk space on a CentOS server hosted on AWS can crash your services, slow down performance, and trigger security risks. In this guide, we’ll show you how we fixed a critical CentOS server disk issue by expanding the attached EBS volume—without any downtime.

Whether you're running blogs, APIs, newsletters, or any Linux-powered service, this post is for you. Let’s dive in with real steps and commands.

🔐 Step 1: Connect to Your CentOS Server via SSH

First, you need to SSH into your CentOS server hosted on AWS.

Requirements:

• .pem key file (downloaded when you launched the instance)
• Public IP or DNS of your EC2 instance
• Default CentOS username: centos

Example Command:

ssh -i "your-key.pem" centos@203.0.113.10

Make sure your .pem file has the right permissions:

chmod 400 your-key.pem

📊 Step 2: Check Current Disk Usage

Once logged in, run:

df -h

You’ll see something like this:

Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p1   50G   48G  1.2G  97% /

If your usage is over 85–90%, your server is at high risk of crashing.

🔍 Step 3: Identify What’s Taking Up Space

To explore top-level disk usage:

sudo du -sh /* 2>/dev/null | sort -hr | head -n 10

Check inside /var, which usually holds logs, databases, and cache:

sudo du -sh /var/* | sort -hr | head -n 10

Tip: If /var/lib/mysql is huge, be careful — that’s your database.

📈 Step 4: Resize the EBS Volume from AWS Console

Go to your EC2 instance on the AWS Management Console:

1. Click Volumes under Elastic Block Store
2. Find the volume attached to your instance (e.g., vol-0a1b2c3d4e5f6g7h8)
3. Click Actions > Modify Volume
4. Change size from 50 GiB to 70 GiB
5. Click Modify and confirm

✅ No reboot or downtime required. Wait until the volume state says "available".

🖥️ Step 5: Log Back In and Resize the Partition

Run the following command to confirm your disk now shows 70G:

lsblk

Expected output:

NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
nvme0n1       259:0    0   70G  0 disk
└─nvme0n1p1   259:1    0   50G  0 part /

Notice the partition is still 50G. We’ll expand it now.

Run:

sudo growpart /dev/nvme0n1 1

Then resize the XFS filesystem:

sudo xfs_growfs -d /

✅ Step 6: Verify the New Size

df -h

Now you should see:

Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p1   70G   48G   22G  69% /

🎉 Your CentOS server now has more room and better performance.

🛡️ Step 7: Set Up Monitoring (Optional but Recommended)

To avoid this in future:

Install UptimeRobot or Similar:

• https://uptimerobot.com

Monitor Disk Space via CLI:

Add this to your crontab:

*/30 * * * * df -h | mail -s "Disk usage alert" your@email.com

Or use CloudWatch metrics in AWS for full automation.

Final Thoughts

Expanding your EBS volume is the safest, most scalable way to fix disk space issues on a live CentOS server—without disrupting service.

This guide works for:

• EC2 Linux instances (CentOS, Amazon Linux, Ubuntu)
• LAMP/LEMP servers
• Blog platforms (WordPress, Ghost)
• Custom apps with growing data

By following these steps, we resolved caching problems, server restarts, and SEO-affecting downtime — all in less than 15 minutes.

Got stuck at any step? Drop a comment or reach out. We’re here to help.