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Computer FAQ

General Questions

E-mail

Printing

Teaching

Mathematical Computation

Web Server

Linux Software

 


General Questions

Q: How do I get an account on the Math department computer system?
A: New faculty and graduate students in the Ph.D. program should see Peter Woit in Room 421 soon after they arrive to set up a computer account. Visitors who are here for more than a day or two and would like to use the computer system should also see Peter about this.

Q: How do I get an account on the main university computer system?
A: All new faculty and students should set up an account on the main university computer system. To do this you need to know your “UNI”, which is generally your initials followed by a number. You should be able to get this from Nathan Schweer. The university web-site for managing UNI accounts is here.

Q: How do I change my password on the Math department computer system?
A: The webmail program (Horde) can be used to change your password. Go to menu item Others/Account/Password.

Q: How do I SSH into the math department server?
A: You can’t. For security reasons users cannot SSH into the server and run executables there (allowing this in the past led to endless breakins due to people having their passwords captured when they used trojaned SSH clients). From any of the department Linux computers you have transparent access to your files and can run any unix software you want to. From outside of the department, basic manipulation of your files is provide by the File Manager feature of the webmail program. If you require a more sophisticated way to manipulate your files, see Peter Woit, who can set up sftp access to the server for you.

Q: I’m at another institution and need Eduroam for network access. How do I set that up?
A: Information about this is available at the Columbia Eduroam page.

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E-mail

Q: Why am I getting so much spam, can’t something be done about it?
A: The math mail server is under continuous attack by an overwhelming amount of spam and virus-laden e-mail. Typically at least 95% of incoming mail is spam or viruses. The server is becoming increasingly heavily loaded trying to deal with this onslaught.

The mail server itself uses three main systems to deal with the problem:

1. The mail server rejects incoming connections from addresses listed on various “BlockLists” which try and maintain lists of addresses used by spammers including PCs that have been trojanned and are being used to send out spam and viruses. The main problem is such PCs, which often each time they are turned on get a new dynamic address. On occasion, legitimate people sending us email find that their mail server is on a blocklist we use, and mail sent here bounces back to them. They will need to have the administrator of their mail server get it off the blocklist.

2. A virus detector called “ClamAV” scans all mail for viruses and rejects virus-laden mail. This is run by a program called MimeDefang, which also rejects all mail containing certain categories of attachments that are rarely used except by viruses.

3. A Spam detector called “SpamAssassin” analyses all the rest of the incoming e-mail and assigns it a score based on a very complex algorithm using many different rules. Higher scores mean higher probability that the e-mail is spam. The algorithms used incorporate Bayesian learning techniques. One reason for some of the random looking spam you see is that it is an attempt by spammers to defeat or poison this kind of analysis. E-mail with a spam score of 5 or above is quarantined. If you have reason to believe an email sent to you has not come through and may be in the quarantine, contact Peter Woit, with any information available about the approximate time the message was sent, and who the sender was.

Users can themselves blacklist sending addresses, automatically deleting email from certain sources. To do this, use the “Blacklist” feature in the “Filters” section of the webmail program. Be aware that it is easy to accidentally blacklist addresses, and if you are not getting email from some source, this may be the problem.

Q: How do I forward e-mail from one account to another, or set a vacation message?
A: To forward e-mail from your central university account, go to the CUIT site that provides management of your UNI account (currently here).

To forward e-mail from your math department account to another one (e.g. to a gmail account), you can use the standard Unix mechanism of creating a file in your home directory with the name “.forward”.  Easier is to go to the “Filters” feature of the Web-mail program and use this (it works by creating a .procmailrc file in your home directory).

The “Filters” feature of the Web-mail program also has a “Vacation” option that you can use to set a vacation message.

Q: How do I read my e-mail on the Math department computer system?
A: The simplest mail programs to use are:

Webmail (Horde): this is a web-based program available here that provides access to your e-mail using the department web-server. It can be used from any web-browser on any computer attached to the internet. The program is started by clicking on “E-Mail and FTP” link in the “Departmental Resources” section on the main department web-page.

Other mail programs (Thunderbird, Outlook, Apple Mail, etc.) can be used to access mail from the math server using IMAP. For information about how to set these up, see this question.

Q: How do I set up my favorite mail program to work with the Math Dept. server?
A: To read your e-mail, you should set the server address to “math.columbia.edu”, and server type to “IMAP” (you should not use “POP” unless absolutely necessary since it can corrupt mail folders, and may not be available in the future). You also need to choose the option to encrypt the connection (“SSL), some programs require you to specify the port (993 for IMAP/SSL), but this is normally set correctly automatically.

To send out e-mail (i.e. to specify the “SMTP server”), you have various options. Note that the “From” line information in your e-mail is set by the e-mail program you use, the SMTP server doesn’t not change the e-mail, it just forwards it to its destination, so, any SMTP server that will let you use it should be fine. Two possibilities are:

  • The main Columbia mail system now is Gmail based, and with your UNI and password you should be able to use the Gmail SMTP server smtp.gmail.com. For more about this, see here.
  • The math department server math.columbia.edu will now act as an SMTP server. This is “authenticated SMTP”, you need to provide your math department username and password. The security setting that should work is “STARTTLS” and if you need to specify a port, try port 587

 

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Printing

Q: What is the Unix name of the printer in (location)?
A: The default printer for the Linux system is the one in Mathematics 421. If you are using this you do not need to specify a printer name. Other printers in semi-public locations are given names according to the scheme “RoomNumber”Printer, e.g. the printer in 421 is 421Printer, the one in the fourth-floor graduate student office is 408Printer. One exception is the color printer in the main office, room 509, which is named 509ColorPrinter. Printers in individual offices are given names according to the scheme “LastName”Printer.

For a complete current list of the department printers, see the CUPS Printers web-page on the Math department web-server.

Q: How do I set up printing to a printer from my Mac or PC?
A: You can print directly from a Mac or PC to any of the departmental printers. When you set this up, the crucial information is the internet name or IP address of the printer, and the type of printer. Here’s a list:

206B: lp206.math.columbia.edu 128.59.192.102 HP Laserjet 600 M601

408: lp408.math.columbia.edu 128.59.192.103 HP Laserjet 600 M601

421: lp421.math.columbia.edu 128.59.192.100 HP Laserjet 4515

509 Color Printer: lp509.math.columbia.edu 128.59.192.101 HP Color Laserjet 500 M551

509 Black and White Printer: lp509bw.math.columbia.edu 128.59.192.116 HP Laserjet 600 M601

Copier on 5th Floor: copier.math.columbia.edu 128.59.192.93 Ricoh Aficio MP 6002

Setting direct printing up is done differently on different operating systems. You may not have the drivers for the precise type of HP printer, but this normally does not matter, you should be able to choose a similar HP model number.

Q: How do I print to the copier, and use the built-in stapler?
A: If you don’t care about using the stapler/collator, you can just print to this like any other printer. It’s internet address is “copier.math.columbia.edu” and you can just use a “generic postcript driver”, or find the correct driver (it’s a Ricoh Aficio MP 6002).

Courtesy of Robert Lipshitz, here’s how to setup the stapler/collator on a Mac:

1. Download the driver from Ricoh: Go to this URL
http://www.ricoh-usa.com/downloads/downloads.aspx
and search for Aficio MP 6002. Select the driver for your operating system.

2. Add the printer. On a Mac, you have to select Line Printer Daemon (LPD), *not* Internet Printing Protocal (IPP).

3. You should get a “extra features” dialogue box. I selected as the “finisher” the SR4060. I don’t know if this is correct, but it currently works.

4. All set. On the Mac, when printing, go to “General 2” under “Printer Features” and select to staple in “Top Left”.

 

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Teaching

Q: What is WebAssign?
A: WebAssign is a system for on-line homework assignments that is integrated with the Stewart Calculus textbook we are using. Calculus instructors will be provided with information about it at the beginning of each semester. For a student FAQ, see here.

Q: What is Courseworks?
A: Courseworks is the university’s on-line course management system. You can use it to set up web-pages for your course, maintain grades, and make available assignments and other material to the students.

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Mathematical Computation

Q: What mathematical software is available through the department?
A: The department Linux machines have installed a wide range of open source mathematical software. If there is some package you would like to use that is not there, please let Peter Woit know and it probably can be installed.

Among commercial packages, Mathematica, Matlab and Magma should be installed on all our Linux workstations. Students who want to install a copy of Mathematica on their own computer can do so using the university’s license: follow the instructions at

https://cuit.columbia.edu/content/mathematica

Students who want to install a copy of Matlab on their own computer will need to buy a copy ($99) directly from the company, see

http://www.mathworks.com/academia/student_version/

Faculty who want to use a copy of Mathematica or Matlab on their own computer, or on a Mac or Windows PC in their office should consult Peter Woit. The department can get licenses for these through the university, although we now are paying for them individually, and no longer have a site license as in the past.

Students or faculty who would like to get a copy of Magma to use on their own machines should consult Peter Woit. The department is now able to acquire such copies through an agreement funded by the Simons Foundation.

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Web Server

Q: How do I create a home page for myself?
A: Your home directory should contain a sub-directory named “html”, and any file you put in it will be accessible to the outside world. If your math department user name is “username”, and you put a file named “file.html” in this sub-directory, it can be accessed as

http://www.math.columbia.edu/~username/file.html

The default file name is “index.html”, so if you create a file with this name, it will be accessible as

http://www.math.columbia.edu/~username

By default the web-server does not list the files in your html directory to the outside world, so one relatively secure way of making files available just to a specific person or small group of people is to just give them an unusual and difficult to guess name. Only people who know the name will be able to access the file.

There are many ways to create html files. Since these are simply text files, the crudest is to take an html file that is close to what you want, and just edit it with a text editor. Modern versions of Microsoft Word, Libre Office, and many other word-processing programs are able to save files in html format. On the Linux systems, the “seamonkey” browser provides a “Composer” mode which allows creation and editing of html files. There are many commercially available full-featured html editors for Mac and Windows, Dreamweaver is perhaps the best known.

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Linux Software

Q: Firefox won’t start, it claims to already be running.
A: First make sure you aren’t logged into multiple linux machines at the same time, with firefox running on another one. Most likely though, this is caused by a failure to automatically delete various “lock” files when firefox terminates abnormally for some reason.

To fix this, you can delete the lock files by hand as follows (you’ll need to open a terminal window, or use the ssh applet on the web-page to ssh login to the server). First make sure firefox really isn’t running (you may want to log out and log back in).

1. Change directory to /home/username/.mozilla/firefox (where username is your username).

cd /home/username/.mozilla/firefox

2. List this directory, you should see a directory name of the form “randomstring.default”

ls

3. Change directory to this directory

cd randomstring.default

4. Remove any files with the names .lock or .parentlock

rm .lock

rm .parentlock

5. Try restarting firefox

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