Mastering SSH: Connecting, Executing Remote Commands and Using Authorized Keys

"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:"

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