Remove fingerprint for RSA Key for SSH connections (remove single line from file via terminal)

Sometimes host key verification fails because the host was replaced, IP has changed or something like this (also it could be a man in the middle attack).

In my case I work with high availability clusters and we often have the case that there is switch of the host. To avoid manual editing of the .ssh/known_hosts file I have written a simple bashrc alias / function.

#simple function to remove a line from .ssh/known_hosts
    if [ x$1 == x ]; then
        echo "Syntax : cleanup_known_hosts Linenumber"
        \cp ~/.ssh/known_hosts ~/.ssh/known_hosts_backup.$$
        sed $1'd' ~/.ssh/known_hosts > /tmp/known_hosts_temp.$$ && \cp /tmp/known_hosts_temp.$$ ~/.ssh/known_hosts
        rm -f /tmp/known_hosts_temp.$$
        echo "Finished"
alias cleanup_known_hosts=cleanup_known_hosts

With small adoptions you can use this function for all situations where you have to remove a given line in a file.