SSH Permission Denied (Publickey) Error on AWS EC2: Authorized Keys Modification

SSH Permission Denied (Publickey) Error in AWS EC2: Authorized Keys Modification

In this article, we will discuss the SSH Permission Denied (Publickey) error that occurs when trying to SSH into an AWS EC2 instance. Specifically, we will cover the modification of authorized keys in the .ssh directory to resolve this issue.

Background

When launching an EC2 instance, a key pair is created to enable secure access to the instance via SSH. The private key is used to authenticate the client, while the public key is added to the authorized\_keys file on the EC2 instance. However, there are instances where this authentication fails, resulting in the SSH Permission Denied (Publickey) error.

Resolving the SSH Permission Denied (Publickey) Error

To resolve this error, we need to modify the authorized\_keys file on the EC2 instance. This can be done using the following steps:

1. Connect to the EC2 instance using a terminal or SSH client.
2. Navigate to the .ssh directory using the command cd ~/.ssh.
3. Check if the authorized\_keys file exists using the command ls -l.
4. If the file exists, check if the public key is present in the file. If not, add the public key to the file using the command echo "public key" >> authorized\_keys.
5. If the file does not exist, create a new file using the command touch authorized\_keys and add the public key to the file.
6. Ensure that the .ssh directory and the authorized\_keys file have the correct permissions. The .ssh directory should have a permission of 700, while the authorized\_keys file should have a permission of 600. This can be done using the commands chmod 700 ~/.ssh and chmod 600 ~/.ssh/authorized\_keys.

Preventing the SSH Permission Denied (Publickey) Error

To prevent the SSH Permission Denied (Publickey) error from occurring, it is recommended to:

1. Create a new key pair when launching a new EC2 instance.
2. Ensure that the private key is kept secure and not shared with anyone.
3. Regularly backup the authorized\_keys file to prevent data loss.
4. Set the correct permissions for the .ssh directory and authorized\_keys file.

The SSH Permission Denied (Publickey) error in AWS EC2 can be resolved by modifying the authorized\_keys file in the .ssh directory. By following the steps outlined in this article, users can regain access to their EC2 instance. Additionally, taking preventive measures such as creating new key pairs, securing the private key, and setting the correct permissions can help prevent this error from occurring in the future.

References

• Authorizing an SSH Key for Your Instance
• Troubleshooting SSH Host Key Verification Failed Errors
• Creating Your Key Pair