juju ssh uses old/invalid known_hosts data

[Joel Griffiths]

2.0-rc3-0ubuntu1~16.04.1~juju1

I've been deploying and destroying openstack (machines and applications) to the same Juju controller. Unfortunately, it doesn't look like the known_hosts data is getting cleaned up between runs. On the plus side, logging in once with the "--no-host-key-checks=true" option seems to fix the data.

me@myhost:~$ juju ssh glance/4
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:Frpe++XF3hV8wNYVrkUzkRK/LB1+v5wq0SUrZC66CS8.
Please contact your system administrator.
Add correct host key in /tmp/ssh_known_hosts126800645 to get rid of this message.
Offending RSA key in /tmp/ssh_known_hosts126800645:7
  remove with:
  ssh-keygen -f "/tmp/ssh_known_hosts126800645" -R 192.168.86.3
RSA host key for 192.168.86.3 has changed and you have requested strict checking.
Host key verification failed.
me@myhost:~$

[Joel Griffiths (joelgriffiths)]

I think this is unrelated to Juju. It looks like a switch was sharing that IP with a container.