Issue
I have created an EC2 Linux Instance in AWS. I used Ubuntu Server 20.04 LTS (HVM) AMI. After create the instance I was downloaded the key pair file (.pem). I gave it a name "EC2-Key-Pair". Then I launched the instance. Then in my Kali Linux system I open a Linux terminal where I saved the .pem file. After that I used this command:
chmod 400 EC2-Key-Pair
After run this command, I used this command:
ssh -i "EC2-Key-Pair.pem" [email protected]
Where ubuntu is the username and
is the Public IPv4 DNS of my instance. But when I executed this command I get this error:
Host key verification failed.
How to fix this error. I have executed this command using sudo and not using sudo. But both way was failed. Even I searched the error on internet, I found a solution that by using this command I can fix this error:
ssh-keygen -R Hostname
Where I used my instance's public IPv4 DNS as Hostname:
ssh-keygen -R ec2-13-232-252-152.ap-south-1.compute.amazonaws.com
But it shows an error that:
Cannot stat /home/sanniddha/.ssh/known_hosts: No such file or directory
Error after execute the SSH command as root user
Error after execute the SSH command
Error after execute ssh-keygen -R Hostname
Solution
The trouble you are getting because of the ssh key fingerprint changed. In general, it is not a bad thing and you accept the warning but double-check everything.
What is an SSH key fingerprint and how is it generated?
What can cause a changed ssh fingerprint
In your case, it might be because you launched an instance earlier and which has a similar DNS name that got added to ~/.ssh/known_hosts file.
xx.xx.xx.xx ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBP2oAPXOCdClEnRzlXuxKtygT3AROcruefiPi6JPdzo+=
You can clean ~/.ssh/known_hosts by issueing following command
ssh-keygen -R ec2-13-232-252-152.ap-south-1.compute.amazonaws.com
As the IP got recycled on AWS side for the instance when you launched a new instance. The new instance has a different ssh fingerprint from the one you have in your ~/.ssh/known_hosts file, hence the warning.
As pointed out already, you need to open port 22 for your IP to access the instance.
If possible use IP address instead of DNS name for ssh. Plus for ssh you don't need sudo
Answered By - samtoddler