Circumventing "Remote Host Identification Has Changed" warning

If you want to pass arguments to a something pre-defined in Bash, you could use a function instead of an alias to the same effect:

ssh-keyrm() { ssh-keygen -f "$HOME/.ssh/known_hosts" -R "$1"; }

Which would be run as such:

$ ssh-keyrm 127.0.0.1

Like aliases, functions can be stored in .bashrc, .bash_profile, or defined inlne in a shell.

you cannot provide an argument to alias

Bash aliases work as simple expansions (the alias name just gets replaced with the alias value), so they cannot reference individual arguments using $n.

However, you can provide arguments as long as they go at the end of the command. With an alias like this:

alias rmh="ssh-keygen -f ~/.ssh/known_hosts -R"

you can run it as rmh 192.168.0.1 and although the word rmh will be expanded, all arguments following it will still remain in the same place.

I have a similar problem with different devices using the same IP, but took a slightly different approach to solve it: prevent the host keys from going in to known_hosts in the first place.

alias sshn='ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no'

Then run sshn whenever you want to disable host key security.

$ sshn [email protected]
Warning: Permanently added '192.168.1.1' (ECDSA) to the list of known hosts.

[email protected]'s password:

ssh tells you it added the host to the known hosts, but it didn't actually since the write went to /dev/null. You can suppress this by fiddling with the logging level, but that may turn off other useful messages.

I also have StrictHostKeyChecking=no so that it skips the authenticity prompt, but if you'd prefer to see the key fingerprint, you can omit that option.