By default we need type remote user’s password to access to remote host with ssh command.This tutorial shows how to configure to access remote host without password.

First,assume:

local host:192.168.1.100
remote host:192.168.1.101,username:username
we want to access to username@192.168.1.101 from 192.168.1.100 without password using ssh

1.Open terminal in 192.168.1.100 machine and type:

ssh-keygen

just press Enter to finish this command and it will create plublic/private rsa key pair:id_rsa,id_rsa.pub

2.Create .ssh directory in remote host which we want to access to.For security,change the permission to 700.
use ssh to access to remote host:

ssh 192.168.1.101 -l username

create .ssh directory and change it’s permission:

mkdir .ssh
chmod 700 .ssh

3.copy and paste id_rsa.pub file from localhost to remote host’s .ssh folder and rename to authorized_keys

scp .ssh/id_rsa.pub username@192.168.1.101:/home/username/.ssh/authorized_keys

Now,use ssh command to access to username@192.168.1.101 from 192.168.1.100 and it won’t ask for password again.
In addition,if it outputs:Agent admitted failure to sign using the key.Try ps -Af|agent to make sure ssh-agent has started.If not,start it and add id_rsa :

ssh-agent
ssh-add id_rsa