No host checking:

ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no $1

No public key, use passwd

ssh -o PreferredAuthentications=keyboard-interactive -o PubkeyAuthentication=no

Tar/untar between hosts:

ssh user@host1 "sudo sh -c 'cd /backups; tar cf - file.tar'" | ssh user@host2 "sudo sh -c 'mkdir /tmp/restore; tar xvf - -C /tmp/restore'"

Multi hop tunnel:

ssh -A -t host1 \
-L 4648:localhost:4648 \
ssh -A -t host2 \
-L 4648:localhost:4648
ssh -A -t host3 \
-L 4648:localhost:4648

SSH Agent:

$ exec ssh-agent /bin/bash

$ ssh-add

-or-

eval `keychain --eval`

http://www.funtoo.org/Keychain

List fingerprints:

ssh-keygen -lf id_rsa

All keys in .ssh/authorized_keys:

( while read L; do echo $L > /tmp/pubkey; printf "%-32s " "$(cut -f3- -d' ' /tmp/pubkey)"; ssh-keygen -l -f /tmp/pubkey; done;  rm /tmp/pubkey ) < .ssh/authorized_keys

Check priv/pub key:

ssh-keygen -y -f id_rsa

Change key passwd:

ssh-keygen -f id_rsa -p