Linux Users

Information for WC CS Department Users

For most purposes, the CS department server is a generic Linux machine, so standard Linux commands do the usual thing. Any reference material for Unix or Linux applies, and there are hundreds of such documents out there, many on the web. If you want to learn how to do something, a web search is a reasonable way to start.

However, there is some information that is specific to our Linux machines, and that information is here.

Locations
The department has ten Linux machines in the Linux lab, AKA the micro-focus. This area is just outside offices E127, E129 and E131. We have another half-dozen machines in SCI 121B, AKA the nano-focus, AKA the Lyn-ex lab. Finally, there are a half-dozen machines in E125 that are dual-boot Windows/Linux (the ``pico-focus''). All the machines are open to SSH and SCP.

Printers
We have configured our machines with four printers. The names of the printers are based on their location:

  • minir: Of the two printers in the mini-focus, this is the one on the right. It's a duplex printer, so if you format your print job for a duplex printer, it will be printed on both sides of the paper. That saves paper (hence our valuable natural resources) and means you have less stuff to carry around.
  • minil: This is the printer in the mini-focus, on the left.
  • e111: This is the printer in the hall across from E111. Like minir, it's a duplex printer.
  • e101: This is the printer outside room E101.

The default printer is "minir," because it's the fastest printer and is duplex, but feel free to direct your print jobs to other printers if minir is busy or broken.
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Soft Deleting of Files
In standard Unix, the "rm" command is used to remove (delete) a file. This operation is permanent and irrevocable, so use it with caution.
Another approach is to mimic the "soft delete" behavior of Windows and Macintosh machines where a file is deleted by putting it in the "trash" or "recycling bin," and where a file that is mistakenly deleted can be taken back out of the trash.
This feature can be useful for anyone, but particularly for novices, so we implemented some shell functions to do soft delete. It works by renaming a file to an "invisible" filename, storing it in the same directory (so, essentially, each directory has its own "trash," which is different from Windows and the Macintosh). All our commands have a long name starting with trash and all but one have a shorthand as well. The command names are:

  • trash-put, srm -- a soft rm; puts the file in the trash of the current directory (by renaming the file to an invisible name).
  • trash-list, tls -- list files in the trash of the current directory.
  • trash-get, urm -- removes a file from the trash (``undeletes'') it.
  • trash-empty, tmt -- permanently deletes all files in the trash of the current directory.
  • trash-empty-all -- permanently deletes all trash files in all your directories. This command has no short-form since it's so sweeping in effect.

Note that these are shell commands, so they are irrelevant for FTP accounts, such as students in CS110 and CS111.
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Quota
Each student account is allowed a limited amount of disk space, currently set at 50MB. She can go over that, up to 100MB total, for a limited time called a grace period. The current grace period is seven days.
If the space limit and grace period are exceeded, you won't be able to login! Therefore, it makes sense to keep track of your quota and usage. To find out about your quota, use the quota command. Here's an example:

[bospre01@puma bospre01] quota
Disk quotas for user bospre01 (uid 2679):

Filesystem
blocks
quota
limit
grace
files
quota
limit
grace
/dev/sdb1
48
50000
100000
 
12
5000
10000
 

The important columns are the "blocks" and "files." This user has 12 files, which is well within the limit of 5000 files. Her 12 files total 48 blocks, so she is also well within the limit of 50000 blocks.

If she had gone over quota, the "grace" column would report the number of days remaining before login is disabled. Use the grace period to clean up, such as emptying the trash and deleting unnecessary files, either by moving them to a zip disk or burning them onto a CD, or just deleting them. Use hard delete (the "rm" command) not soft-delete, since soft-deleted files still exist and still count against quota.

If you are on a special project or have some other reason to need additional disk space, contact the system administrators and we will be happy to grant more disk space, assuming there is space available.

If you are near your quota limits, here are some things you can do:

  • delete unnecessary files. Do a "spring cleaning" of your account; it's amazing the kind of stuff that can accumulate.
  • clean out "soft-deleted" files, using the trash-empty-all command.
  • clear your browser cache in Mozilla:
    • Go to Edit > Preferences
    • From the toolbar on the right, open the "Advanced" option, which will reveal the "cache" option. Click on this.
    • To clear your cache, use the "Clear Disk Cache" button located on the right-hand side of the menu.
    • To help you say below quota, you might also reduce your disk cache to something more modest, such as 2,000KB (2MB) or 5,000KB (5MB) out of your 50MB quota.
  • clear your browser cache in Firefox:
    • Go to Edit > Preferences
    • Select "Privacy" from the menu on the right hand side
    • Click the clear icon next to the word cache
  • to clear your browser cache from the command prompt
    • type cd ~/.mozilla/default/*/Cache/ and then rm *
    • or type cd ~/.mozilla/firefox/*/Cache/ and then rm *
  • delete redundant files. For example, if you have a foo.java file and its compiled form, foo.class, and the .class file can easily be regenerated from the .java file, you can save some space just by deleting the .class file.
  • compress files or directories. Suppose you want to keep all your .java files from CS111, for sentimental value, but you don't need instant access to them. You can convert the entire directory tree into a single file and compress that file. Compression of plain text files is often very good, compressing them to a third or less of their original size. Here are the steps, supposing you want to delete your ~/cs111 directory tree:
  • % cd
  • % tar czf cs111.tgz cs111
  • % rm -r cs111
  • To get the files back again, do:
  • % tar xzf cs111.tgz
  • If you can't login because you have been over quota too long, you can delete files via FTP. (Fetch on Macs, WS_FTP on PCs.)

To find out which directories and files are using the marjority of your quota you can use the du command. Below is an example:
[kbenson@finch ~] du ~ | sort -nr | more
91876   .
23784   ./public_html
18316   ./.mozilla
10840   ./public_html/cgi-bin
10772   ./public_html/cgi-bin/sports
9752    ./math251
8772    ./.mozilla/firefox
8664    ./.mozilla/default
8660    ./.mozilla/default/f230ucw4.slt
7076    ./.mozilla/default/f230ucw4.slt/Cache
....
--More--

You can read more of the list by pressing enter, and quit out of the list by pressing q.
If you do not have access to a shell you can still check your quota.
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Backup
You should also know that every night we do a backup to disk of all files, so if you accidentally delete a file that you created the day before, such files can usually be restored. Contact the system administrators for help.
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Connecting to NTM
If you want to connect to NTM (a Windows machine), the easiest thing to do is use Samba, which is software that allows Linux machines to connect to Windows machines.

  • On the RedHat menu, choose "Places"
  • choose "connect to server"
  • select "Windows Share" from the drop-down menu
  • type "NTM" under "Server"
  • click "Connect". That pops up an authentication window.
  • give your domain username for the username
  • put "WELLESLEY" as the domain name
  • give your domain password for the password.

This will open up a window that will let you navigate to the place you want, such as "24 hour drop." You will also see "NTM" as an icon on your desktop, wher you can re-open the window.
The setup is "sticky," in that you should continue to see NTM on your desktop and it should also appear in the "places" menu, even after logging out.
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What's Up?

BYTE OF THE WEEK 

 

Wellesley seniors majoring in CS present tecnical posters at Wellesley's first CS Senior Poster Fair, April 16th.

 

NEWS

Now offering new courses "Computing and Life" (CS249) and "Quantifying Data Privacy" (CS349) this semester!

 

MIT's App Inventor 2 launched last week, with 9 Wellesley students contributing to its improvements this past semester in MIT 6.s198 and in research projects.

 

This fall, Wellesley students participated in the Grace Hopper Conference, ICPC Programming Contest, and the Capture the Flag contest.

 

Contact Us

 

Ellen Hildreth
Department Chair 
Tel: 781.283.3025
ehildret@wellesley.edu

 

Rita Purcell
Administrative Assistant 
Tel: 781.283.3151
rpurcell@wellesley.edu