Understanding the Issue

When working with Amazon EC2 instances, it’s not uncommon to encounter an EBS (Elastic Block Store) volume that fails to mount upon reboot. This can happen due to the volume being stuck in a “Busy” or “Attaching” state, or due to Input/output errors within operating systems such as Ubuntu. This issue may also arise when mdadm cannot reassemble a RAID array on the EBS volume.

Diagnosing the Problem

The problem often presents itself when an EBS volume, say /dev/sdi, does not properly attach to an EC2 instance. In the Amazon AWS console, the status may persist as “attaching” or “busy,” or in Ubuntu, the device might show Input/output errors or not appear in /dev at all, impeding file operations and system functions.

Step-by-Step Resolution Guide

The following is a structured approach to troubleshoot and resolve the issue with the EBS volume:

    1. Force Detachment: Begin by “Force Detaching” the problematic volume from your EC2 instance within the AWS console.
    2. Clean the Local Device References: On your Ubuntu system, refresh the block device information and check for the device presence using the following commands:

  % sudo blkid -g
  % ls /dev/sd*
    1. Remove Stale Device Node: If the problematic /dev/sdi still appears, remove this stale device node to prevent conflicts:

  % sudo rm /dev/sdi
  1. Reattach to a New Device: Back in the AWS console, reassign the EBS volume to a different device, such as /dev/sdg (confirm it’s not already in use), and then proceed to attach the volume.
  2. Update File System Configuration: Modify the /etc/fstab entry to reflect the new device assignment by replacing /dev/sdi with /dev/sdg, and then attempt to mount the volume:

Finalizing the Solution

After successfully attaching and mounting the EBS volume to the new device node, ensure that any applications or services that depend on this volume are updated to reference the new device location. This will help to avoid any future service disruption.

Conclusion and Preventative Measures

While the resolution to this issue is typically straightforward, it underscores the importance of regular monitoring and maintenance of cloud infrastructure. To prevent potential data access issues or service downtime, consider implementing automated checks and alerts for your volumes’ statuses. Additionally, familiarize your team with AWS’s best practices for EBS management to mitigate similar problems in the future.

Need Further Assistance?

If the problem persists or if you require more in-depth support, please consult AWS’s documentation or contact their support team for professional assistance.