==== SSH ====
=== generate key ===
<code>
$ ssh-keygen -t rsa -b 4096
</code>
=== ssh agent ===
If your private key is encrypted with a passphrase(when you generate it by ssh-keygen), the passphrase must be entered every time you attempt to connect to an SSH server using public-key authentication.

SSH agent is a program which caches your decrypted private keys and provides them to SSH client programs on your behalf.

<code>

$ eval $(ssh-agent)

$ echo $SSH_AUTH_SOCK

$ ssh-add (add ~/.ssh/id_rsa by default)

$ ssh -T user@remote.com
</code>

=== forwarding of authentication agent connection ===
-A enables forwarding of the authentication agent connection.
local -> server1 -> server2
<code>
$ eval $(ssh-agent)
$ ssh-add
$ ssh -A server1
<host1> $ ssh server2
</code>


=== ssh tunnel ssh -L ===


== How to access the Database Home Page "http://127.0.0.1:8080/apex" remotely using ssh tunnel. ==

  - install sshd package on your local machine
  - add a line in /etc/sshd/sshd_config<code>
AllowTcpForwarding yes
</code>
  - restart sshd service
  - ssh to start tunnel<code>
ssh -L 8081:localhost:8080 <oracle db host>
</code>
  - login to db web admin console http://localhost:8081/apex
  - login with 'SYS' account, then click the 'Administration' button, 'Tasks - Manage HTTP Access' , then enable HTTP access from remote clients.

== SSH file transport ==


  $ tar -cf - xen_el5_i386_para | gzip -c -9 | ssh root@ostest117 "gzip -dc | tar -xf - -C /OVS/rpool"
  $ tar czf - xen_el5_i386_para | ssh root@ostest117 "tar xzf - -C /OVS/rpool"
  
  
 ==== Reference ===
  - https://wiki.archlinux.org/index.php/SSH_keys