CentOS6.4 ssh-agent : access to SSH servers without entering password

referred to http://www.atmarkit.co.jp/flinux/rensai/linuxtips/447nonpassh.html

Both SSH server and SSH client are CentOS6.4.

I have already installed openssh on both boxes.

SSH server allows accesses from remote boxes with root user.

on the SSH server, create keys

# ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is:

here are keys

# pwd /root/.ssh # ls id* id_rsa  id_rsa.pub

id_rsa: private key

id_rsa.pub: public key

on the SSH server, make authorized_keys by using id_rsa.pub key.

# cat id_rsa.pub >> ~/.ssh/authorized_keys # chmod 600 ~/.ssh/authorized_keys

copy id_rsa key to SSH client from SSH server.

confirm the key is the same on both boxes.

on the SSH server

# md5sum id_rsa a79523e3e7cdbe1fbfc822d26f80b427  id_rsa

on the SSH client

# md5sum id_rsa a79523e3e7cdbe1fbfc822d26f80b427  id_rsa

on the SSH client, start ssh-agent

# ssh-agent SSH_AUTH_SOCK=/tmp/ssh-muDsy12684/agent.12684; export SSH_AUTH_SOCK; SSH_AGENT_PID=12685; export SSH_AGENT_PID; echo Agent pid 12685;

on the client, add id_rsa key.

error..

# ssh-add id_rsa Could not open a connection to your authentication agent.

Googling this error, the solutions on this seems to be:

stop ssh-agent daemon

# ps aux | grep ssh-agent | grep -v grep root     12685  0.0  0.0  57360   708 ?        Ss   16:23   0:00 ssh-agent # kill 12685

start ssh-agent again.

Okey, I was able to add id_rsa

# eval `ssh-agent -s` Agent pid 12709 # ssh-add id_rsa Enter passphrase for id_rsa: Identity added: id_rsa (id_rsa) # ssh-add -l 2048 xx:xx:xx id_rsa (RSA)

access to the server.

required to enter password..

# ssh root@192.168.10.211 'whoami' root@192.168.10.211's password: root

Oops, I need to use hostname instead of IP

# ssh root@sshserver 'whoami' root