amazon ec2 - Unable to connect from ec2 server -

i trying login on ec2 instance server, getting me errors

too many authentication failures ubuntu,

or

permission denied (public key).

when connect server ssh -i "pem_file" ec2_name@public_ip

when yesterday, login in server, it's worked after exit server , again trying login it's giving me errors mentions above.

so if message

too many authentication failures ubuntu,

it's because have tried many private_keys authenticate against user ubuntu in server.

you can more info here:

https://superuser.com/questions/187779/too-many-authentication-failures-for-username

try running this:

ssh-add -l ssh-add -d  

you may have many keys stored in local ssh-agent.

if this:

permission denied (public key).

generally means public key not in ~ubuntu/.ssh/authorized_keys file on server. can debug creating snapshot of ebs volume (if using ebs). create new volume snapshot , attach volume running ec2 instance.

http://docs.aws.amazon.com/awsec2/latest/userguide/ebs-attaching-volume.html

that way can see what's in /home/ubuntu/.ssh/ directory

hope helps.