get the hash value of EBS

Hi Vikram,

If you really need a hash of the volume content, you can create a script that runs when your EC2 instance starts up.

The script would:

• Briefly mount the EBS volume.
• Use md5sum or a similar tool to calculate the hash.
• Store the hash in a secure location (like an S3 bucket).
• Unmount the volume.

Here the Basic example script.

#!/bin/bash

DEVICE="/dev/xvdf"
BUCKET_NAME="my-s3-bucket"
OBJECT_KEY="ebs-volume-hash.txt"

sudo mount $DEVICE /mnt/ebs
VOLUME_HASH=$(md5sum /mnt/ebs/ | cut -d ' ' -f 1)
aws s3 cp --quiet /tmp/ebs-hash.txt s3://$BUCKET_NAME/$OBJECT_KEY
sudo umount /mnt/ebs
rm -f /tmp/ebs-hash.txt
echo "EBS volume hash uploaded to s3://$BUCKET_NAME/$OBJECT_KEY"

replace the placeholders with your specific values:

• DEVICE: The device name of your EBS volume.
• BUCKET_NAME: The name of your S3 bucket.
• OBJECT_KEY: The desired filename within the S3 bucket

EBS Snapshots with ETag info: https://docs.aws.amazon.com/ebs/latest/userguide/ebs-creating-snapshot.html

md5sum command explanation: https://community.linuxmint.com/tutorial/view/346

Hi

To get the hash value of an EBS volume without mounting it, you can use the AWS CLI along with a tool like dd to read the raw data and a hashing tool like sha256sum to compute the hash.

Use the dd Command to Read the Raw Data:

• SSH into your EC2 instance.

• Use the dd command to read the raw data from the EBS volume and pipe it to a hashing tool.

• sudo: Run the command with root privileges.

• dd if=/dev/xvdf bs=4M: The dd command reads from the input file (if) which is the EBS volume device (/dev/xvdf) with a block size (bs) of 4 megabytes.

• |: The pipe symbol directs the output of the dd command to the next command.

• sha256sum: This command calculates the SHA-256 hash of the input.