Troubleshooting • ssh key problems

My search skills are failing me. So are my Linux skills. So asking for a little help here.

I have two Pi both running RPiOS Trixie. A Pi5 installed a while ago but recently updated and a 500+ running with the OS installed yesterday and updated today.

Both have identical usernames, identical $HOME/.ssh/authorized_keys, and identical /etc/ssh/sshd_config files.

In case it matters all keys are rsa.

If I add the Pi5's public key to the 500+'s authorized keys ssh from the 5B works as expected.

I can ssh into the PI5 with putty and key-based login just worksTM. Using the same client PC, the same putty binary, and the same key set the 500+ shows no error but always prompts for a password and ignores the key(s).

They do have different files in /etc/ssh/sshd_config.d.

The Pi5 has Both have 50-cloud-init.conf in /etc/ssh/sshd_config.d/ which is empty.

The 500+ has /etc/ssh/sshd_config.d/50-cloud-init.conf which contains:
# SPDX-License-Identifier: LGPL-2.1-or-later
#
# Allow connecting to the local host directly via ".host"
Host .host machine/.host
ProxyCommand /usr/lib/systemd/systemd-ssh-proxy unix/run/ssh-unix-local/socket %p
ProxyUseFdpass yes
CheckHostIP no

# Make sure unix/* and vsock/* can be used to connect to AF_UNIX and AF_VSOCK paths.
# Make sure machine/* can be used to connect to local machines registered in machined.
#
Host unix/* vsock/* machine/*
ProxyCommand /usr/lib/systemd/systemd-ssh-proxy %h %p
ProxyUseFdpass yes
CheckHostIP no

# Disable all kinds of host identity checks, since these addresses are generally ephemeral.
StrictHostKeyChecking no
UserKnownHostsFile /dev/null
]Neither were put there by hand.

I suspect I'm missing something obvious...

Edited to correct mistake pointed out below.

Statistics: Posted by thagrol — Wed Sep 23, 2026 3:21 pm — Replies 7 — Views 30

---