I have 3 RHEL machines that were installed approximately the same time. Two of the three ssh RSA key login works as expected, but the third machine, RSA key login has never worked. It always requires a pw.

During my investigations, I discovered that ~/.ssh/known_hosts does not get updated, and is empty, despite having logged in from a number of machines.

I have compared /etc/ssh/sshd_config and the pam defs with the working machines, and cannot find any descrepencies.

/var/log/secure does get updated.

Can anyone enlighten me to why no updates to known_hosts. What am I missing?

Okay, have found another symptom, by turning on DEBUG, and the secure log shows ssh cannot open anything in ~/.ssh . So I will research the reasons for this.

Check permissions on the .ssh directory and known_hosts. Also look for errors in the logs.

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What user/perms are on ~/.ssh? What user are you logging in with?

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follow the links in my sig, they should help.

It turns out that permissions for the entire system were wonky. I re-installed the OS, and now everything works. Thanks to all who replied.

Note on RHEL and other RPM-based systems system perms can be restored (see 'man rpm') so reinstalling the OS really should be a last resort option.