Shell script to update the .ssh/known_hosts file for all users on a given machine when the host key of a target machine has changed

update_known_hosts.bash

TARGET_HOST=prometheus

# for each user with a home directory
for USER in `ls /home`; do

    # if the user has a known_hosts files
    echo "checking /home/$USER/.ssh/known_hosts..."
    if [ -f /home/$USER/.ssh/known_hosts ]; then

        # remove the outdated key
        ssh-keygen -R $TARGET_HOST -f /home/$USER/.ssh/known_hosts

        # append the new host key
        ssh-keyscan -H $TARGET_HOST | grep ssh-rsa >> /home/$USER/.ssh/known_hosts
    fi

done