Replication failing: authentication failure

TrueNAS General
1

Hi There,

We have a backup TrueNAS (2022), which is used to back up a TrueNAS file server on our local network, plus several FreeBSD workstations. This has worked flawlessly for years until today, when we tried to back up the file server and started receiving authentication errors. Here’s the log:

[2025/12/09 18:36:46] INFO [Thread-13] [zettarepl.paramiko.replication_task__task_3] Connected (version 2.0, client OpenSSH_8.8-hpn14v15)
[2025/12/09 18:36:46] INFO [Thread-13] [zettarepl.paramiko.replication_task__task_3] Authentication (publickey) failed.
[2025/12/09 18:36:46] ERROR [replication_task__task_3] [zettarepl.replication.run] For task ‘task_3’ non-recoverable replication error ReplicationError(‘Authentication failed.’)

We haven’t changed anything, and I can still log in to the backup server using the existing keys (I don’t have to type a password, in other words).

I’ve tried recreating the connections, this hasn’t changed anything. It still fails, but now instead of reporting the snapshot that was last saved, it says “nothing saved yet”. This is also concerning, because a couple of our FreeBSD systems are thousands of miles away and not over the fastest connection, so we are dependent on the incremental backup feature so we don’t have to backup the entire system remotely.

auth.log on the Fileserver is interesting. It says it doesn’t accept ssh-rsa, (those are the TrueNAS entries), but at the end, it accepts my root login using RSA just fine. But I can’t find anyplace in the UI to edit PubkeyAccepterAlgorithms:

Dec 9 18:16:27 freenas 1 2025-12-09T18:16:27.226396-07:00 freenas.local sshd 2002 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:16:27 freenas 1 2025-12-09T18:16:27.577291-07:00 freenas.local sshd 2004 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:24:01 freenas 1 2025-12-09T18:24:01.255485-07:00 freenas.local sshd 2089 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:24:01 freenas 1 2025-12-09T18:24:01.261150-07:00 freenas.local sshd 2090 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:24:19 freenas 1 2025-12-09T18:24:19.917686-07:00 freenas.local sshd 2093 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:24:20 freenas 1 2025-12-09T18:24:20.263237-07:00 freenas.local sshd 2095 - - userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Dec 9 18:36:14 freenas 1 2025-12-09T18:36:14.046463-07:00 freenas.local sshd 2217 - - Accepted publickey for root from 192.168.1.12 port 27401 ssh2: RSA SHA256:fvtGOc4LIn1pg/gR330lIaaNxL5FcDDAPUAVyMGu5yg

Thanks in advance for any help,

Pammy

2

So I fixed it. You don’t want to know how so I won’t mention it.

The most interesting thing is that the incompatibility was only between the TrueNAS systems, the others still worked beautifully.

Have a nice day there.

Pammy