Remote access to accounts

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In order to work in a remote way inside your student's account of the Telematics Department, there are 4 computers available for an SSH connection.

Those computers are:

MONITORS for REMOTE ACCESS (monitor0X.lab.it.uc3m.es)

Host name IP CPU RAM Hard Disk Driver IDE-SATA Driver Tarjeta Red (eth0)
monitor01.lab.it.uc3m.es 163.117.144.156 Intel Pentium 4 (2.4 GHz) 1 GB 40 GB pata_sis sis900
monitor02.lab.it.uc3m.es 163.117.144.157 Intel Pentium 4 (2.4 GHz) 1 GB 60 GB pata_sis sis900
monitor03.lab.it.uc3m.es 163.117.144.140 AMD Athlon(tm) XP 1800+ (1.5GHz) 1 GB 40 GB vt8235 8139too
monitor04.lab.it.uc3m.es 163.117.144.141 AMD Athlon(tm) XP 1800+ (1.5 GHz) 1 GB 40 GB vt8235 8139too


Remote Access via SSH from Windows

Windows does not have a default SSH client, because of that we will use a free-client: "PuTTY". You can download it from: PuTTY. This does not need any installation, because it is just an exe. If we execute it, we will have an screen like this one:

Connection example to monitor01.lab.it.uc3m.es

In the field "Host Name (or IP address)" you must write the host name (monitor0X.lab.it.uc3m.es, being X the monitor number) or its IP address (look the table above).

The session type must be SSH (TCP 22 port).

You can save the hostname and its options in order not to introduce them again in future connections. If in gap "Saved Sessions" you write a name for the ssession and then click to button "Save"; the adjustments data will be saved for future connections. Later on, you will only need to click the one you want and push "Load"):

Saved Sessions List
















After that configuration, if you click button "Open", you will start the SSH session with the monitor. Probably, mainly if it is the first time you are connecting to that monitor; a warning will pop up to add the RSA key to cache. You have to click "Yes" and then a prompt will show up asking for the user and password:

Warning for saving rsa2 key
Ssh4.jpg

















For closing the session you can do it with exit command or just closing the window.


For using the graphics mode you need to import the X.

You need to have installed the Xmig application or any similar one. You can download this app in the following link: http://sourceforge.net/projects/xming/?source=dlp

Firstly, you must start Xmig app before doing the connection. You have to configure the connection with Putty, besides the earlier configuration, as you will see in the following image.

You have to select, in Connection category, the X11. In the options that appears on the rigth-hand side you have to select Enable X11 forwarding and then do the connection.

PUTTY3.JPG

Remote access via SSH from Linux

On the opposite, usually the Linux distributions already have a default ssh client (ssh command). Let's see an example of how you have to connect by ssh from Ubuntu 8.04 ( it will be good for any version and for Debian).

In Ubuntu, you will install (if you do not have it yet) a free ssh server and a free ssh client: openSSH, with the command:

 sudo apt-get install openssh-client openssh-blacklist

In a way that if you want to connect to monitor01, for example, you will use the command "ssh" form a shell, as following:

 ssh -l 0934456 monitor01.lab.it.uc3m.es

There we have that -l is followed by the NIA without the initial 10, and then you write the host name of the computer that you want to connect to. It is important to write an user, if you do not write an user the ssh will, by default, ask for a password but without knowing the user, you will not be able to enter.

In the case that you want to export the X's and then see the graphic environment, you will have to configure the file /etc/ssh/ssh_config previously. For this configuration you will have to do the following:

 sudo gedit /etc/ssh/ssh_config
 Delete # from line: ForwardX11 yes

Now, you have to add the -X option when you are connecting. For instance:

 ssh -X -l 0934456 monitor01.lab.it.uc3m.es
Connecting with "ssh -X" to monitor01 for the account 0934456. We say "yes" to the security warning.
We execute the command "xeyes" in order to check that we see perfectly the graphics environment. We can also try with eclipse, ekiga...

Issues with the <sudo> command in order to export the application

The problem is due to account permissions because the accounts are exported by NFS. This does not work because the user root cannot access to the $HOME/.Xauthority file and then it cannot authenticate the access to the graphic account.

       monitor01:~> ls -las .Xauthority
       4 -rw-------  1 0022212 22212 3118 Aug 13 18:26 .Xauthority
       monitor01:~> sudo ethereal
       X11 connection rejected because of wrong authentication.
       X connection to localhost:10.0 broken (explicit kill or server shutdown).
       
       If you change the permission by 604...
       monitor01:~> chmod 604 .Xauthority
       monitor01:~> ls -las .Xauthority
       4 -rw----r--  1 lab 22212 3118 Aug 13 18:26 .Xauthority
       monitor01:~> sudo ethereal
       Now it works

Besides, you have to have at least a 701 permission in the $HOME of your account. The solution to this will inccur in a security fail, because anyone can reed the file .Xauthority and execute an application in the local Xs.

Advanced Information

You can send an email to guru@adm.it.uc3m.es if you have any issue.

X11 exporting in UBUNTU

SSH server in UBUNTU