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cp EC2keypair .ssh/id_rsa
chmod 0600 .ssh/id_rsa
#ssh-copy-id 192.168.1.100 ( it's not needed because we already use the same key pair from AWS )
ssh 192.168.1.100
Other option would be to create an password for the centos user ( AWS centos EC2 instance ) + allow password in SSHD config + restart the process
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