The ubuntu16.04 server is configured with ssh passage free login

Operate on the client side

ssh-keygen -t rsa

File location to write/home try /. ssh/server_rsa, I named server_rsa about it, do not use the default values affect git key (because I git is using a default value)

ssh-copy-id root@123.45.56.78 (your server ip),

Or the use

cat ~/.ssh/id_rsa.pub | ssh user@123.45.56.78 "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"

You can upload your client key to the server's ~/.ssh /authorized_keys file, or manually copy it in.

Operate on the server side

sudo nano /etc/ssh/sshd_config

Change this to without-password to achieve root free login

Namely PermitRootLogin without - password

ssh shorthand tips

vim ~/.ssh/config

add

Host lisa, easy to remember

HostName 188.166.225.189 your server ip

User root

Port 9999 (port optional, not recommended) (I didn't use the last two, but the first three are enough)

IdentityFile ~/.ssh /id_rsa certified key location, if it has already been sent to the server, do not use this

ssh lisa can be used instead of ssh root@188.166.225.186