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Logging In and Out

To enter the system you need to identify yourself, what is known as logging in the Linux machine. How you do it depends on how you access the system and how it is configure.

Logging In the system directly from a (text) terminal

If you do it in a text terminal, just type your user name at the prompt; you will be asked for your password; type it and you are in the system (if you did not do any mistake).

Logging In the system directly from an X-windows session

To log on in a X-windows terminal you will find a small window with a "Logging" Type your user name, and then your password; you will then go to an X-windows session.

Logging Out of the system from a (text) terminal

To log out (exit) of a text teminal, type logout

Logging Out of the system from an X-windows session

To exit an X-windows session, use the mouse; click on the right buttom of it and choose the "Logout" or "exit" option.

Accessing the system from a remote terminal

If you want to access the system from outside (or some machine in the system remotely from another machine) you have several options:

  1. ssh: secure shell, allows you to access a (remote) computer with security (the connection will be encrypted, and thus difficult to break). Just to
        ssh remote-computer
    If you are outside the School of Maths sytem, then the only computer you can acess by this way is

    You can also execute commands with something like

       ssh remote-computer command-to-be-executed
  2. rsh: remote shell, to log on in a remote computer with a command like
        rsh remote-computer

    Or execute a command with

        rsh remote-computer command-to-be-executed
    The difference between ssh and rsh is that the latter does not encrypt the data, so important things like password and other commands can (in principle) be read by an outside machine.
  3. telnet: similar to the two commands above except that you can only access a system, there is no provision for executing commands in a remote machine (well, you can do it after you are logged on in the remote machine). The command is similar
       telnet remote-computer
    and the connection is not encrypted.

Problems while Logging Out of the system

Some times the system will complain when you try to log out, with a message of the type There are stopped jobs and will not exit you from your session. In that case, you can try one of the following things:

  1. Type jobs; the output is of the following form:
        [1]+ Stopped    less /etc/services
    Then you can call the job by doing
        fg %1
    and finish it. Log out after that. Or you could kill the job with
        kill %1
        kill -9 %1
    and then log out.
  2. Type
        kill -9 -1
    The disadvantage of this option is that it will kill any job that you are running. For example, if you left some long computation running it will be finished.

Problems while Logging Out with remote access

If you have problems to log out of a session that you started with ssh or rsh just type

For a session initiated with telnet type
that is, the "Control" key and the ] at the same time.
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