|Resources and Services
Frequently asked questions (FAQ)
- 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
- Do we have a ftp server? I need to upload/download files when I am traveling.
This service is discontinued for off campus access.
- 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.
- 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.
- 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.
- 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:
ssh email@example.com -L 2000:
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.
- 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%.
- How do I run a MPI program on Benny?
Set environment variable LM_LICENSE_FILE (set by default):
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
View current job queue: condor_q
View current pool status: condor_benny