"Earlier I said that "ssh" stands for "secure shell." ssh is
very concerned about security. The message "The authenticity of
host '192.168.1.20 (192.168.1.20)' can't be established" shows this
security focus. This message just means my ssh client doesn't know
the remote server. I use the word "client" here and throughout this
article because the ssh command line utility initiates the network
connection and that makes it, by definition, a network client.
"After informing me that it didn't know the remote server, the
utility then asked me if I wanted to continue connecting. I
answered "yes" because I knew that the server I was connecting to
was the server I really intended to connect to. Typically, it is
safe to answer "yes" to this question. The danger, though, is that
some bad person with questionable motives might be impersonating
the server you are attempting to connect to. After I answered "yes"
to continue connecting, my ssh client updated the file
$HOME/.ssh/known_hosts with the following text:"