generate key in linux

#192.168.10.220: generate key: public key(like a door), private key(like a key)
ssh-keygen -t rsa
mv id_rsa /root/.ssh/sj221.key
scp id_rsa.pub 192.168.10.221:/root/.ssh/  # move public key to 221


#192.168.10.221: setup the door(public key) into 221
cat /root/.ssh/id_rsa.pub >> /root/.ssh/authorized_keys # add public key(door) into authorized_keys
rm /root/.ssh/id_rsa.pub

#192.168.10.220: open the door
ssh -i /root/.ssh/sj221.key 192.168.10.221