[amazon-web-services] Add Keypair to existing EC2 instance

I was given AWS Console access to an account with 2 instances running that I cannot shut down (in production). I would, however, like to gain SSH access to these instances, is it possible to create a new Keypair and apply it to the instances so I can SSH in? Obtaining the existing pem file for the keypair the instances were created under is currently not an option.

If this isn't possible is there some other way I can get into the instances?

I didn't find an easy way to add a new key pair via the console, but you can do it manually.

Just ssh into your EC2 box with the existing key pair. Then edit the ~/.ssh/authorized_keys and add the new key on a new line. Exit and ssh via the new machine. Success!

You can actually add a key pair through the elastic beanstalk config page. it then restarts your instance for you and everything works.

Once an instance has been started, there is no way to change the keypair associated with the instance at a meta data level, but you can change what ssh key you use to connect to the instance.

stackoverflow.com/questions/7881469/change-key-pair-for-ec2-instance

You can just add a new key to the instance by the following command:

ssh-copy-id -i ~/.ssh/id_rsa.pub domain_alias

You can configure domain_alias in ~/.ssh config

host domain_alias
  User ubuntu
  Hostname domain.com
  IdentityFile ~/.ssh/ec2.pem

On your local machine, run command:

ssh-keygen -t rsa -C "SomeAlias"

After that command runs, a file ending in *.pub will be generated. Copy the contents of that file.

On the Amazon machine, edit ~/.ssh/authorized_keys and paste the contents of the *.pub file (and remove any existing contents first).

You can then SSH using the other file that was generated from the ssh-keygen command (the private key).

This happened to me earlier (didn't have access to an EC2 instance someone else created but had access to AWS web console) and I blogged the answer: http://readystate4.com/2013/04/09/aws-gaining-ssh-access-to-an-ec2-instance-you-lost-access-to/

Basically, you can detached the EBS drive, attach it to an EC2 that you do have access to. Add your SSH pub key to ~ec2-user/.ssh/authorized_keys on this attached drive. Then put it back on the old EC2 instance. step-by-step in the link using Amazon AMI.

No need to make snapshots or create a new cloned instance.

In my case I used this documentation to associate a key pair with my instance of Elastic Beanstalk

Important

You must create an Amazon EC2 key pair and configure your Elastic Beanstalk–provisioned Amazon EC2 instances to use the Amazon EC2 key pair before you can access your Elastic Beanstalk–provisioned Amazon EC2 instances. You can set up your Amazon EC2 key pairs using the AWS Management Console. For instructions on creating a key pair for Amazon EC2, see the Amazon Elastic Compute Cloud Getting Started Guide.

Configuring Amazon EC2 Server Instances with Elastic Beanstalk

For Elasticbeanstalk environments, you can apply a key-value pair to a running instance like this:

• Create a key-value pair from EC2 -> Key Pairs (Under NETWORK & SECURITY tab)
• Go to Elasticbeanstalk and click on your application
• Go to configuration page and modify security settings
• Choose your EC2 key pair and click Apply
• Click confirm to confirm the update. It will terminate the environment and apply the key value to your environment.

Though you can't add a key pair to a running EC2 instance directly, you can create a linux user and create a new key pair for him, then use it like you would with the original user's key pair.

In your case, you can ask the instance owner (who created it) to do the following. Thus, the instance owner doesn't have to share his own keys with you, but you would still be able to ssh into these instances. These steps were originally posted by Utkarsh Sengar (aka. @zengr) at http://utkarshsengar.com/2011/01/manage-multiple-accounts-on-1-amazon-ec2-instance/. I've made only a few small changes.

1. Step 1: login by default “ubuntu” user:

   $ ssh -i my_orig_key.pem [email protected]
   

2. Step 2: create a new user, we will call our new user “john”:

   [ubuntu@ip-11-111-111-111 ~]$ sudo adduser john
   

   Set password for “john” by:

   [ubuntu@ip-11-111-111-111 ~]$ sudo su -
   [root@ip-11-111-111-111 ubuntu]# passwd john
   

   Add “john” to sudoer’s list by:

   [root@ip-11-111-111-111 ubuntu]# visudo
   

   .. and add the following to the end of the file:

   john   ALL = (ALL)    ALL
   

   Alright! We have our new user created, now you need to generate the key file which will be needed to login, like we have my_orin_key.pem in Step 1.

   Now, exit and go back to ubuntu, out of root.

   [root@ip-11-111-111-111 ubuntu]# exit
   [ubuntu@ip-11-111-111-111 ~]$
   

3. Step 3: creating the public and private keys:

   [ubuntu@ip-11-111-111-111 ~]$ su john
   

   Enter the password you created for “john” in Step 2. Then create a key pair. Remember that the passphrase for key pair should be at least 4 characters.

   [john@ip-11-111-111-111 ubuntu]$ cd /home/john/
   [john@ip-11-111-111-111 ~]$ ssh-keygen -b 1024 -f john -t dsa
   [john@ip-11-111-111-111 ~]$ mkdir .ssh
   [john@ip-11-111-111-111 ~]$ chmod 700 .ssh
   [john@ip-11-111-111-111 ~]$ cat john.pub > .ssh/authorized_keys
   [john@ip-11-111-111-111 ~]$ chmod 600 .ssh/authorized_keys
   [john@ip-11-111-111-111 ~]$ sudo chown john:ubuntu .ssh
   

   In the above step, john is the user we created and ubuntu is the default user group.

   [john@ip-11-111-111-111 ~]$ sudo chown john:ubuntu .ssh/authorized_keys
   

4. Step 4: now you just need to download the key called “john”. I use scp to download/upload files from EC2, here is how you can do it.

   You will still need to copy the file using ubuntu user, since you only have the key for that user name. So, you will need to move the key to ubuntu folder and chmod it to 777.

   [john@ip-11-111-111-111 ~]$ sudo cp john /home/ubuntu/
   [john@ip-11-111-111-111 ~]$ sudo chmod 777 /home/ubuntu/john
   

   Now come to local machine’s terminal, where you have my_orig_key.pem file and do this:

   $ cd ~/.ssh
   $ scp -i my_orig_key.pem [email protected]:/home/ubuntu/john john
   

   The above command will copy the key “john” to the present working directory on your local machine. Once you have copied the key to your local machine, you should delete “/home/ubuntu/john”, since it’s a private key.

   Now, one your local machine chmod john to 600.

   $ chmod 600 john
   

5. Step 5: time to test your key:

   $ ssh -i john [email protected]
   

So, in this manner, you can setup multiple users to use one EC2 instance!!