I have a shell login on host cheddar.halon.org.uk, while I was away for a few days recently (that bit's irrelevant really), cheddar.halon.org.uk was (presumably) moved to an new machine and thus its host key changed.
So, when I came home, my passwordless login to cheddar.halon.org.uk failed with the usual ssh message about 'host key has changed', maybe a man in the middle attack, etc.
I removed the relevant line from ~/.ssh/known_hosts, logged in again, the correct line was added to ~/.ssh/known_hosts and all was well again, or so I thought.
However, it doesn't all work again as it did:-
While ssh logins to cheddar.halon.org.uk from terminal windows on my GUI desktop are passwordless logins from shell console terminals (i.e. CTRL/ALT/n ones) ask for my password at cheddar.halon.org.uk (N.B. they don't ask for the key to my passphrase, it's the cheddar.halon.org.uk password that is asked for). I'm sure these used to work.
More to the point my rsync backup to cheddar.halon.org.uk that runs as a cron job has also stopped working, it's expecting a passwordless login to cheddar.halon.org.uk but like the ssh login from a console it's failing because cheddar.halon.org.uk is asking for a password.
So both the above problems point at some sort of screw up with ssh_agent but it's complicated by the following:-
The file ~/.ssh/config contains:-
Host cheddar.halon.org.uk IdentityFile ~/.ssh/np_id_rsa
and ~/.ssh/np_id_rsa and ~/.ssh/np_id_rsa.pub haven't changed so why isn't it being used?
Any ideas as to what else might have been affected by the host key change at cheddar.halon.org.uk? It's possible some previous misconfiguration was masking something such that the passwordless login was working for some other reason than the config file above but I still need to sort it out.