ssh -V
nc [servername] 22
ecdsa-sk
ed25519-sk
$ ssh-keygen -t ecdsa-sk -f ~/.ssh/id_ecdsa_sk
$ ssh-keygen -t ecdsa-sk -O resident -f ~/.ssh/id_ecdsa_sk
$ ssh-add -K
yubikey-agent.
sekey
ssh -A
.ssh/config
ServerAliveInterval 5ServerAliveCountMax 1
ssh
ServerAliveInterval
ServerAliveCountMax
~
~.
~?
tmux attach
tmux