How to change/update key pair for ec2 instance – AWS

NEW and Easy way:

1. Login to AWS Console. Go to the Network and Security >> Keypair.
2. Give the name of your keypair (mykeypair) and keytype (RSA) and Private keyformat (.pem). and click on the create keypair. It will ask you to download .pem file in your local machine. Save it at and remember the location.
3. Login to your EC2 instance and go to the .ssh. location. Create a new file called (mykeypair.pem) and paste the content from the file we downloaded in step no.2
4. Run the command: sudo chmod 600 mykeypair.pem
5. Run the command: ssh-keygen -f mykeypair.pem -y and it will generate some content. Copy that content. Open the file called autherized_keys (in your root .ssh folder) and remove all the content from it.
6. Paste the copied content that we have generated in the previous step. Also enter your file name (mykeypair) in last after entering space.

7. Reboot your instance. Go to the puttygen and generate the .ppk file using the pem file you have downloaded from the keypair. You will be able to login your ec2 with the newly generated .ppk from putty.

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(Old and NOT recommended... Instruction from AWS EC2 support:)

1. Log into your AWS account
2. go to your EC2 Console
3. Under NETWORK & SECURITY, click on Key Pair Click on Create Key Pair
4. Give your new key pair a name, save the .pem file. The name of the key pair will be used to connect to your instance
5. Create SSH connection to your instance and keep it open
6. in PuttyGen (https://www.puttygen.com/), click "Load" to load your .pem file
7. Keep the SSH-2 RSA radio button checked. Click on "Save private key" You'll get pop-up window warning, click "Yes”
8. click on "Save public key" as well, so to generate the public key. This is the public key that we're going to copy across to your current instance
9. Save the public key with the new key pair name and with the extension .pub
10. Open the public key content in a notepad
11. copy the content below "Comment: "imported-openssh-key" and before "---- END SSH2 PUBLIC KEY ----
    Note - you need to copy the content as one line - delete all new lines
12. on your connected instance, open your authorized_keys file using the tool vi. Run the following command: vi .ssh/authorized_keys you should see the original public key in the file also
13. move your cursor on the file to the end of your first public key content :type "i" for insert
14. on the new line, type "ssh-rsa" and add a space before you paste the content of the public key , space, and the name of the .pem file (without the .pem) Note - you should get a line with the same format as the previous line
15. press the Esc key, and then type :wq!

this will save the updated authorized_keys file

now try open a new SSH session to your instance using your new key pai

When you've confirmed you're able to SSH into the instance using the new key pair, u can vi .ssh/authorized_key and delete the old key.