Using MTL » Computation

Getting Help

Frequently Asked Questions


Quick Help

The best way to request help is to send email to the appropriate mailing list described below. Your request gets copied to a collection of staff (and in some cases students and faculty) with knowledge in that particular problem area. This is much better than sending email to any one staff member who may be unavailable that day.


You are also welcome to drop in on the compute staff (39-651). Please note that they may be in the middle of something and so may not be able to resolve your problem at that instant. The staff may ask that you send a message to problems@mtl so that we are sure to log and track the problem.


Frequently Asked Questions

Emergencies

Accounts and Passwords

Network Storage

CAD Issues (but may apply to others as well)

Backups

Computer Setup

 

Emergencies

How do I contact you in an emergency?

What do I do if I think my machine has a virus?

 

Accounts and Passwords

I want to change my password. How do I do that?

I forgot my password. How do I reset it?

I'm confused. What passwords go with what account?

 

Network Storage

What is the Z: drive?

How do I mount the Z: drive manually?

How do I use the Z: drive?

 

CAD issues

On UNIX machines, what should the path to network files look like?

Remote Connection Problems

It seems that many CAD users are Using VNC to connect remotely to the
MTL CAD servers or their own research group servers.  Many folks may not be aware that because VNC is not inherently secure, it is highly recommended to tunnel your VNC connection through SSH.  Because of this, we're sending around the following general HOW TO guide that describes how to get VNC set up and to run it securely through SSH.

In this example, we’ll use your_group’s_unix_server as the remote server to connect to. This is not the name of an actual server. You should replace it with the name of your group’s unix server. If you do not know the name, ask us and we will help you figure it out but it is usually the server where your unix home directory (the Z: drive) is stored.

As always, these are meant to be general notes to help people get setup and not exact step by step notes that will work for everyone.  Depending on the client computer that you're Using, your exact steps needed to be done may differ a bit.  If you have any questions/problems on how to get VNC and SSH set up for your particular computing environment, please send a message to problems at mtl.mit.edu and we'll try to help you.

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Prerequisites:
--------------

(A) You will need a SSH client program installed on your client
computer. e.g. SecureCRT which is freely available from MIT for Windows.

(B) You will need a VNC client viewer program installed on your client
computer. e.g. http://www.realvnc.com/products/free/4.1/download.html

NOTE: If you're client computer is a RedHat 4 or 5 Linux workstation
then you can use the built in VNC and SSH clients that are available.

---------------------------------------------------------------------------

NOTE: If you've already run a VNC server within MTL before then you can
probably skip steps 2-4.

1. Login/SSH to your_group’s_unix_server.mit.edu

2. Run the following command:

    % vncserver

    Enter a password for your VNC sessions. Note the session number
    that is created. It will look something like:

       >your_group’s_unix_server:/homes/bmaloney% vncserver
       >
       >New 'your_group’s_unix_server:34 (bmaloney)' desktop is your_group’s_unix_server:34

    Where the session number in this example is 34


3. Edit/Create your VNC xstartup file found in ~<your MTL username>/.vnc

Something like this should work:

#!/bin/sh

opers=`uname -s`

if [ $opers = "Linux" ]
then
    exec /etc/X11/xinit/xinitrc
else
    /usr/dt/bin/dtwm &
    /usr/dt/bin/dtterm &
    /usr/dt/bin/dtterm &
fi


4. Run the following command to end the session created above:

    % vncserver -kill :<session number from above>

    ( e.g vncserver -kill :34 )


5. Run vncserver again and specify a session number

% vncserver :<N>  -localhost -NeverShared=true -DisconnectClients=false

   where <N> = a number for your session e.g. 34

   ( e.g. vncserver :34 -localhost -NeverShared=true -DisconnectClients=false )

The other arguments listed will increase the security of your session by not allowing anyone to try and connect to it from another computer and by not allowing it to be shared.  In addition, it will not disconnect a currently connected session if another connect request comes in.  So, make sure to always disconnect your session when finished if you tend to connect from multiple clients during the day.

Now that you have a session running, you can connect to it in a secure
way from a remote client computer.

(A) Connecting from a Windows desktop client computer
     -------------------------------------------------

Run SecureCRT (these notes are specific to SecureCRT 6)

Choose Connect from the File menu

Right click on Sessions and choose New Session

Choose Protocol: ssh2 and click Next
Enter the hostname: your_group’s_unix_server.mit.edu
Enter your unix username
Click Next until you reach the page with Finish on it
Change session name to "your_group’s_unix_server-VNC"
Click Finish

Right click on the new session and choose Properties

Choose Port Forwarding from the left hand menu
Choose Add
Enter your_group’s_unix_server-VNC for the name

Enter local port: 5900 + <M> (where M is any number typically the same
as the session number above but see the note below about running
multiple VNC client sessions on the same machine). ( e.g. 5934 )

Enter remote port: 5900 + <N> (where N must be number of the vncserver
session from above). ( e.g. 5934 )

Enter the vncviewer client for Application e.g.
C:\Program Files\RealVNC\vncviewer\vncviewer.exe

Enter "localhost:<P>" for the arguments (where P must be the same as M
above). ( e.g. localhost:34 )

Click OK until you close out of all dialog boxes.

Highlight the new session and choose 'Connect'


(B) Connecting from a RedHat Linux desktop client computer
     ------------------------------------------------------

Open up a terminal window and run the following command:

% ssh -L <local port>:localhost:<remote port> -N your_group’s_unix_server.mit.edu

where

<local port> = 5900 + <M> (where M is any number typically the same as
the session number above but see the note below about running multiple
VNC client sessions on the same machine).

<remote port> = 5900 + <N> (where N must be number of the vncserver
session from above).

Open up another terminal window and run the VNC viewer command:

% vncviewer localhost:<M>

where

<M> = the same as <M> in the ssh directions above.

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IMPORTANT NOTE: If you have more than one VNC client session running,
you'll need to choose a different local port for each of them.  In other words, if you had separate sessions on mtlcad and your_group’s_unix_server then one would use 5960 and the other 5961.  If do you choose the same local port, they can't both run at the same time.

Backups

Is my machine being backed up?

My machine was backing up, but it isn't anymore. What happened?

What information do you need in order to restore my files from backups?

With that information, we can then see about restoring the files for you from the MTL backups (assuming the computer is being backed up by us).

 

Computer Setup

I found a computer on a junk pile – can I add it to the network and be supported?

Can I set up my computer myself?

Why does my laptop need a permanent IP address?

I heard that computers that use DHCP are free. Why should my supervisor pay a machine fee?

Computation

MTL Annual Research Report 2017: View Online