accounts_and_labs:the_linux_network Technical Support

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===== SCS Linux Network =====

{{  :accounts_and_labs:ubuntu.jpg?100|SCS is using Ubuntu}}

Here you will find the steps to create and access the SCS Linux network

{{:accounts_and_labs:lambda.png|}}


==== Introduction ====

The School of Computer Science is running:

  * Ubuntu 10.04 Desktop
  * has 16 machines on the 'lambda' network (lambda01-16)
  * uses X-Win32 for (X11) connections via the SCS Windows Labs
  * uses [[services:external_access_host_access | access.scs.carleton.ca]] as the external gateway; the lambda machines are not visible from outside of the school's network
  * user home directories are mounted on all 16 lambda's

\\

==== Creating a Linux Account and Eligibility ====

Linux Account eligibility:

    * Any SCS student taking a computer course that requires linux
    * any BCS or SCS graduate student

If you need to create a linux account or simply want to change your linux password (online account system link):

http://www.scs.carleton.ca/webacct/

More information on creating a linux account can be found here: [[account_creation|Account Creation Instructions]]

==== Logging into the Linux Network ====

There are two ways to enter the SCS Lambda Linux network:

  - Connecting to Linux using Windows using an X-emulator (graphical) application 
  - External gateway [[services:external_access_host_access | access.scs.carleton.ca]] (non-graphical)

\\

=== Connecting to Linux using Windows ===

You can run an X-emulator on Windows that will allow you to display graphical applications ((in Linux they are called X11 applications)) that you launch remotely from the linux hosts. The X-emulator that is installed in the SCS labs is called X-Win32.

== Putty ==

Putty is an ssh client that is available free of charge for Windows. With putty you can log into the SCS linux/lambda network. Putty is a command line application.

== X-Win32 ==

X-Win32 is a Windows X-emulator application. It allows you to launch graphical/X11 linux applications and display them on a Windows machine. X-win32 is installed in the SCS Windows labs ((X-Win32 is a commercial application which means it requires a license)).

The X-Win32 application can be run in many ways, two of them are as follows:

  - Run X-Win32 and use putty to launch applications
  - Run X-Win32 in XDMCP mode that allows you to login remotely

== X-Win32 and putty ==

You can start X-win32 and then use putty-ssh to launch applications from linux. The way you can do this is as follows:

  - Log onto the SCS Windows machine
  - Launch X-Win32 (All Programs - Xwin32 8.1 - X-Win32)
  - Start Putty ssh
  - Putty Config: Host Name enter: access.scs.carleton.ca
  - Putty Config: Connection Type: ssh
  - Putty Config: Category - Connection - SSH - X11 - X11 forwarding - Enable X11 forwarding
  - Putty Config: Press OPEN
  - login using your SCS login and password
  - on the access prompt: ssh -X lambdaXX (where XX is lambda01-16) 
  

Then you can spawn off programs on the putty command line, example: 'xterm &' and they should pop-up on your Windows environment.

== X-Win32 and remote sessions ==

You can run X-Win32 in XDMCP mode that will allow you to login to the lambda machines remotely. This gives you the same environment as if you were sitting in front of the linux terminal, similar to remote desktop under Windows.

You can configure X-Win32 to run a remote linux session as follows:

  - Start X-Config: All Programs - X-Win32 8.1 - X-Config
  - Press the New Session - 'Manual...' Button
  - Connection Method XDMCP-  then press Next
  - Session Name: lambda 
  - XDMCP Mode: Indirect
  - Host: Choose one of 134.117.27.XXX, where XXX=30,74,75,76,107,109,111,122,129,130,134,135,188,199,200 Example: 134.117.27.111
  - Monitor: 1 (default)
  - Then Save
  - in the X-Config window click on 'My Session' - lambda and then the Launch button
  - Once a connection is made you will get a chooser of lambda hosts, select one and press Connect
  - log into the lambda host using your SCS account and password 

\\

=== External gateway: access.scs.carleton.ca ===

The lambda machines are behind the SCS firewall, to access them remotely you need to login to the SCS gateway [[services:external_access_host_access | access.scs.carleton.ca]].


To log into the lambda's remotely use your favorite ssh client and lambda:

<code>
ssh access.scs.carleton.ca -l jdoe
[jdoe@access ~]$ ssh lambda07
============================================================
 __     Welcome to the SCS    __          __              
/\ \                         /\ \        /\ \             
\ \ \         __      ___ ___\ \ \____   \_\ \     __     
 \ \ \  __  /'__`\  /' __` __`\ \ '__`\  /'_` \  /'__`\   
  \ \ \L\ \/\ \L\.\_/\ \/\ \/\ \ \ \L\ \/\ \L\ \/\ \L\.\_ 
   \ \____/\ \__/.\_\ \_\ \_\ \_\ \_,__/\ \___,_\ \__/.\_\
    \/___/  \/__/\/_/\/_/\/_/\/_/\/___/  \/__,_ /\/__/\/_/
                                   Linux Network

          Questions: support@scs.carleton.ca
       Online: http://www.scs.carleton.ca/nethelp/
============================================================
lambda07:~>
</code>

==== Remote Host Identification Error ====

Do you receive the following error?

<code>
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
64:1f:1e:50:76:f1:5d:d3:ff:d0:93:4c:e8:73:a9:56.
Please contact your system administrator.
Add correct host key in /home/4user1/hsimpson/.ssh/known_hosts to get rid of this message.
Offending key in /home/4user1/hsimpson/.ssh/known_hosts:21
RSA host key for lambda01 has changed and you have requested strict checking.
Host key verification failed.
</code>

This is due to a software and hardware upgrade. What you need to do is ssh to access.scs.carleton.ca and then delete the file ~/.ssh/known_hosts and the ssh key will be re-generated ((You could also edit the known_hosts file and remove the offending key)).



==== Process Killer ====

There is a process killer installed on the lambda network. It runs once a day and checks for all processes that are:

  * not nice'd 
  * older than 24 hrs

If it meets the above criteria it will kill the process.

=== How to use nice ===

The //nice// command assigns a low priority number to your process. Say you want to run your program called //my_program// then you can run your program nice'd as follows:

<code>nice my_program</code>

If you already have a running process you can //renice// it. ((For more info type //man renice// in a terminal window))


==== Hardware ====

Here are some of the specs for the Linux Network hardware:

  * lambda01-12: Intel(R) Core(TM)2 CPU 6600  @ 2.40GHz
  * lambda13-16: Intel(R) Core(TM)2 Quad CPU Q6600  @ 2.40GHz 
  * 4 GB RAM
  * lambda13-16: ASUS ENGTX480 videocards
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