SSH - Secure shell

SSH is a program for logging into a remote machine and for executing commands on a remote machine.
SSH provide secure encrypted communications between two untrusted hosts over an insecure network.
We can use four "type" of connection:
-1 -> try only protocol version 1
-2 -> try only protocol version 2 (RECCOMENDED)
-4 -> try only IPv4
-6 -> try only IPv6
Default protocol is 2 because provide additional mechanisms for confidentiality and integrity.
Syntax : ssh [options] [user@]hostname [command]
To connect you must specified hostname with user(optional).
If command is specified, it is executed on the remote host instead of a login shell.
With options -A you can enable authentication agent connection, instead with option -a you can disable authentication agent connection.
If you use more than one address you can specified the address of the connection with option -b
-b address
You can also compress all data with options -C. The compression algorithm is the same used for gzip.
For encrypting the session we can use -c chiper
For more informations about encrypting see config file (ssh_config)
-f : Requests ssh to go to background just before command execution.
To specify the user to log in use options -l login_name
With option -n you can redirect stdin into /dev/null
The default port for ssh is 22. You can specify the port with options -p port
You can also enable (-X) or disable (-x) the x11 forwarding.
For more informations about ssh you can see the manual of ssh (type man ssh).

If you have a problem or you need some explanations just write under this post!