The cool dr.calix writes:

issue: Authentication failed for user ubuntu@xx.xxx.xxx.xxx (Net::SSH::AuthenticationFailed) via capistrano but can ssh directly

debugging:

• sudo tail -f /var/log/auth.log on the server
• then tried cap production deploy:check on my local
• userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth] appeared from auth.log

solution:

• edited then /etc/ssh/sshd_config
  • find PubkeyAuthentication then uncomment(remove #)
  • add PubkeyAcceptedKeyTypes=+ssh-rsa
• restart sshd sudo systemctl restart sshd