Debian Jessie: add ssh key into remote server

Requirement:

• openssh
• rsync

Create key pair in your host is straight forward:

$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/foo/.ssh/id_rsa):
Created directory '/home/foo/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/foo/.ssh/id_rsa.
Your public key has been saved in /home/foo/.ssh/id_rsa.pub.
The key fingerprint is:
XXXXXX foo@SERVER_A
The key's randomart image is:
....

You have to copy foo's public key into remote site

Method 1: Manual copy public key to remote

on host

$ scp -P 22 ./.ssh/id_rsa.pub bar@SERVER_B:/home/bar/
The authenticity of host '[SERVER_B]:22 ([SERVER_B]:22)' can't be established.
ECDSA key fingerprint is XXXXXX.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[SERVER_B]:22' (ECDSA) to the list of known hosts.
bar@SERVER_B's password:
id_rsa.pub                                    100%  390     0.4KB/s   00:00

on remote site

$ cat /home/bar/id_rsa.pub >> /home/bar/.ssh/authorized_keys

Method 2: Direct add public key to remote

$ ssh-copy-id -p 22 bar@SERVER_B
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
bar@SERVER_B's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh -p '22' 'bar@SERVER_B'"
and check to make sure that only the key(s) you wanted were added.

Done, you can ssh using user bar @ SERVER_B without entering password (using your key), from foo @ SERVER_A.

References:

• http://www.debian.org/devel/passwordlessssh
• https://help.ubuntu.com/community/SSH/OpenSSH/Keys