RSA based authentication to NX-OS without local user (remote auth)

Hello there,

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I am in the process of automating my Cisco-switch-management. My goal is to authenticate without passwords to all my cisco-switches. For Cisco-IOS it is already working (switch has TACACS enabled and I just added the public RSA key to the pubkey-chain, so no local user on the switch). I can log on with my private RSA key and I see the login auth on my TACAS server.

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For NX-OS I can't figure this out. There is no option to add keys to a pubkey-chain. According to the docs I would do "username aduser sshkey file bootflash:aduser.key.pub". Unfortunately, NX-OS does not allow this: "account is already created through remote authentication".

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Any tip/hint would be appreciated.