Levich webpage http://www-levich.engr.ccny.cuny.edu is on a new server   : Levich mail server migrated.
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Frequently asked questions (FAQ)

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Computing service:

  1. How can I access cluster computers from my home?
    The best way to access cluster computers from home is through a campus computer. If you do not have a workstation in campus, you can request an account on www-levich.engr.ccny.cuny.edu from the system administrator. All activities on this login server are monitored and recorded.

  2. Do we have a ftp server? I need to upload/download files when I am traveling.
    This service is discontinued for off campus access.
  3. Why did my Dreamweaver (or other ftp programs) drop ftp connection sometimes?
    It is not quite clear why this happens. It might be related to the firewall and port numbers available on your computer. One side of the FTP uses dynamic unprivileged port numbers, which could be filtered by firewall, depending on the firewall of either your side and campus side. Switching passive and active mode allow dynamic unprivileged ports be used on client or server side, and it might solve the problem.

  4. How to encrypt and decrypt a file on Unix?
    This works on OS X, Linux, anywhere with Open SSL installed:
    To encrypt a file:
    openssl des3 -salt -in infile.txt -out encryptedfile.txt
    To decrypt the file:
    openssl des3 -d -salt -in encryptedfile.txt -out normalfile.txt
    The command will prompt password input and you will need the same password to decrypt the file.

  5. Why did my ssh connection dropped once a while?
    If you use tcsh, system has a auto-logout feature. To disable this function put line "set autologout=0" in your .cshrc or .tcshrc file.

  6. How do use levdec to send emails when I work at home?
    One way is to use the web interface https://levdec.engr.ccny.cuny.edu
    Another way is to use ssh tunneling:
    UNIX:
    ssh user@levdec.engr.ccny.cuny.edu -L 2000:levdec.engr.ccny.cuny.edu:25
    The above command says "log in to levdec, forward local port 2000 to remote server port 25". The reason to use local port 2000 is local port under 1024 are previllaged and requires root to do the port forwading.

    You also need to set up your email client to use localhost port 2000 in the SMTP (outgoing email server) configuration.

  7. Is there a spam filter on levdec?
    Yes, spambayes is a serverside spam filter.  However you have to use IMAP to access the server at the training stage. Ask your sysadmin to setup this for you.

    Once the filter is set up, your will see these three mail folders on your IMAP server: inbox, unsure, and spam. Move spam mails to spam folder and move non-spam mails to inbox. Keep mails in inbox and spam folders for one day so that the server has a chance to train the filter. After a few days, the accuracy will be increased to 99%.


Programming

  1. How do I run a MPI program on Benny?
    Set environment variable LM_LICENSE_FILE (set by default):
    export LM_LICENSE_FILE=/usr/pgi/license.dat

    Compile:
    mpicc -o executable_name source1.c source2.c ...
    mpicxx -o executable_name source1.cpp source2.cpp ...
    mpif77 -o executable_name source1.f source2.f ...
    mpif90 -o executable_name source1.f source2.f ...

    Test, test mpi for up to 4 processors on master:
    mpirun -np 1|2|3|4 executable_name

    Run, submit with condor job scheduler:
    sample submit description file: /home/condor/submit
    http://www-levich.engr.ccny.cuny.edu/~comp/tutorials/condor.php
    View current job queue: condor_q
    View current pool status: condor_benny