Friday, July 26, 2013

OPENSSH-SERVER


SSH is program to login into remote computer in Network. You can have all accessibility when you logged into remote computer. This is done by Linux terminal. You can also login from Windows to Linux System but you must have the Public key and password of the remote System, but for Linux you just need password of remote system. As I mention in the  beginning of this blog SSH is a program from which you can login into remote System. But it is must that Remote System must have Openssh-server installed in its system.

You can read more about SSH program by typing “man ssh” on your Linux terminal, as shown below.

Fig :1
In above image you can see at left most corner is given “SSH(1)”, that 1 means its “Executable programs or shell commands”. In Linux there are different types of programs that run on Linux Terminal. For example there is one command that is “kill()” which can be use for two different purposes.

You can check program type by typing on terminal “man man”, it shows following output on terminal as below.

Fig : 2

As mention we must have Openssh-server on Remote system, following is an example for installing Openssh-server in your system.
For installing openssh-server:

    sudo apt-get install openssh-server

Fig :3
You can also download openssh-server(any package) instead of installing it for later use.

For downloading openssh-server:

        sudo apt-get download openssh-server

Fig:4
Now, to connect to remote System you have to type on your terminal,

          ssh -4 IP_Address_of_Remote_System

Fig:5
In above command I used “-4”, which indicate that it's a IPV4, for IPV6 use “-6”. When you'll try to login into Remote host, it will ask for the Remote account password for security purpose. After logged into Remote Host you can have all access to Remote host on your terminal. But for Administrative or root access you must know it's password. To access as Administrative or root you can switch to that account by typing on terminal:

      su account_name

It will ask you the password for the same account. After entering into that account you can have access as Admin or root.

Many times it happened that you login as Admin but you can't use some commands like poweroff . So for that purpose just try following command,

       sudo poweroff

Here, it will ask for the Admin Account password, type it and then you can use some of the root command easily.