Amazon AWS - EBS Volume Deletion on Instance Termination

This post explains how to set the DeleteOnTermination flag for an AMI image so that on down-scaling, you don't have to clean up all the EBS volumes that have been retained (which incur extra cost)

Prerequisites:

• AWS Cli 
• in ubuntu, apt-get awscli will install this, you will need to run aws configure post installation
• AMI image which currently have the DeleteOnTermination flag false (When you click on the AMI, see the 'Block Devices'. /dev/sda=snap-snapshot_id:10:false:gp2  - The false indicates that the volume won't be deleted upon instance termination)

Step 1 (Optional) :

Run 

aws ec2 describe-images --image-ids ami-image_id

You will see the details of the image and you can spot   "DeleteOnTermination": false 

Step 2:

What you are going to do is to register a new AMI, which is a clone of the original AMI (with the DeleteOnTermination flag false) and set the DeleteOnTermination flag while registering. And the following command achieves this:

aws ec2 register-image --name "AMI New"  --block-device-mappings "[{\"DeviceName\": \"device_name_of_old\",\"Ebs\": {\"SnapshotId\": \"snap-snapshot_id_of_old_ami\",\"VolumeSize\": volume_size_of_old_ami,\"DeleteOnTermination\": true,\"VolumeType\":\"volume_type_of_old\"}}]"  --architecture architecture_of_old --virtualization-type virtualization_type_of_old --kernel-id kernel_id_of_old --root-device-name "root_device_name_of_old" 

If the command was successful, you will receive the Image ID of the newly registered AMI, which you can use in your code for up-scaling and down-scaling without worrying about unused volumes piling up. You can verify the change by redoing step 1 and replacing the ami-image_id with the image_id of the new AMI

JSON to HTML - Display JSON as a list in HTML

Many-a-times it is required to print list out your json object in html, like when you are testing your API and api produces the out put as json. The following javascript function may be used to print your json object as a neat html un-ordered list

function json_to_html(json) 
{

   ret = "";
   ret += "<ul>";
   for( i in json) 
   {
      ret += "<li>"+i+": ";

      if( typeof json[i] === "object") 
         ret += json_to_html(json[i]);
      else 
         ret += json[i];
          
     ret += "</li>";
   }
   ret += "</ul>";
   return ret;
}

Converting Putty ppk file to pem in Ubuntu

First you need to install putty tools. You may either install putty from the Software Center or use the following command in terminal

sudo apt-get install putty-tools

Converting the ppk file to pem file 

Use puttygen to convert ppk to pem

sudo puttygen /path/to/ppk/file.ppk -O private-openssh -o /path/for/saving/pem/key.pem

Copy the key.pem to ~/.ssh path 

sudo cp /path/of/pem/key.pem ~/.ssh/

Set file permission for ~/.ssh/key.pem 

sudo chmod 400 ~/.ssh/key.pem 

Use the pem key to ssh to the remote system 

sudo ssh -i ~/.ssh/key.pem user@your.systems.ip.address