clear known hosts

Two ways to do this:

1. Clean out the known hosts file with sed

sed -i '18 d' ~/.ssh/known_hosts


Note that this will only work with GNU sed. For unix systems, you will need to do something like:

sed -e "18d" ~/.ssh/known_hosts > ~/.ssh/known_hosts.temp
mv ~/.ssh/known_hosts.temp ~/.ssh/known_hosts


2. Clear out the known hosts file with ssh-keygen

/usr/bin/ssh-keygen -R /