Error: Error waiting for SSH: Packer experienced an authentication error

Error: Error waiting for SSH: Packer experienced an authentication error

TL;DR

Packer reached the instance over SSH but could not authenticate. Check the username matches the AMI (ec2-user, ubuntu, admin), the keypair is the one Packer created or the one you pointed at, and Packer is connecting over the right interface.

The error

==> amazon-ebs: Error waiting for SSH: Packer experienced an authentication error when trying to connect via SSH. This can happen if your username/password are wrong. You may want to double-check your credentials as part of your debugging process. original error: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain

Fix it

1. Verify the username for your source AMI: Amazon Linux uses ec2-user, Ubuntu uses ubuntu, Debian uses admin. A wrong username fails exactly like this.

• Success check: ssh_username matches the AMI's default user.

1. Check which IP Packer dials. If the instance has no public IP or you are in a private subnet, set ssh_interface to private_ip (and run the build where that is routable); if it needs the public IP, use public_ip.

• Success check: the SSH target is reachable from the build machine.

1. If you set ssh_private_key_file, confirm the file exists and matches the keypair Packer associates. If you let Packer generate a temporary keypair, make sure your IAM identity is allowed to create keypairs.

• Success check: no UnauthorizedOperation on keypair creation in the log.

1. Run with PACKER_LOG=1 and look at the handshaking with SSH lines to see which methods were attempted.

• Success check: the log shows which side rejected the auth.

When to use this

You hit this after the instance launches, at Waiting for SSH to become available, on any builder using the SSH communicator.

When NOT to use this

Do not use this for SSH timeouts where nothing answers (security groups, no route). This error means something answered and rejected the credentials.

Compatibility

Packer 1.x, all SSH-based builders (amazon-ebs, googlecompute, vsphere-iso, qemu, etc.).

Variants

• attempted methods [none password] (password auth attempted; wrong password or user)
• attempted methods [none publickey] (key auth attempted; wrong key or user)
• The same error on vsphere-iso, qemu, and other builders

Root cause

SSH reached the host but no offered credential was accepted. The usual culprits are a wrong ssh_username for the AMI, Packer dialing an IP the key was not authorized for, or a manually specified key that does not match.

Edge cases

• Custom AMIs with hardened SSH configs may disable the auth method Packer uses. Compare against a stock AMI first.
• ssh_timeout only extends the wait; it does not fix authentication. Do not raise it expecting auth to start working.