Timothy Nohe
Assistant Professor of Visual Art
IMDA Graduate Program Director
Office hours: Friday 3:30 - 5:30 PM
FA 342, 410-455-2151

nohe@research.umbc.edu

Working with pub space in your UMBC gl accounts:

We can share files and work as a virtual community of digital artists by using "pub space" as a common file sharing resource.

Pub directories are commonly used to share non-proprietary information, software, images, etc. World Wide Web sites are typically served from a pub space, and anonymous FTP sites serve files open to the public from such directories. Web sites hosted by gl accounts at umbc, are nested inside pub/www. A symbolic link leads Internet users to a path that looks like this:

http://www.gl.umbc.edu/~cwong4/

The illustration at right points to the absolute path name of several ART 610 users. The absolute pathname to a directory may be typed directly in the opening interface screen of Fetch, illustration below right, or may be reached by navigating through directories.

To move into another person's directories one must first go to the /afs/umbc.edu/users path, then change directories to the first character of their username, then change directories to the second character of their user name, then enter their personal directory, for example cwong4. Finally, enter their pub directory to find shared files. The result of that path navigation would look like this:

/afs/umbc.edu/users/c/w/cwong4/pub

We will share files from our pub directories for the rest of the semester.

Note that this does not illustrate the full path, which is:/afs/umbc.edu/users/n/o/nohe/pub

Uploading "permissions" in Fetch:

UNIX can be used to link multiple users through networks, both at the local level and at a global level. Networked communication and routing protocols allow a user to communicate with a workstation two desks away, or a continent away. This system makes possible the sharing of data, from recipes to MP3 files. It is very important to note that any shared social space is predicated on trust, transparency and security. We must act responsibly and proactively to assure the security of our accounts, web sites, etc. You will be responsible for learning how to protect yourself, and your peers from hackers and security breaches.

UNIX allows users to set "permissions" (imagine your personal security code) first for personal use, then for local members among a "group" of collaborators, and finally for the "world," which one may imagine as the Internet.

Reading "permissions" in UNIX:

By typing ls -l at a UNIX prompt you may find out the current security status of any files or directories within your account. ls -lg provides additional information as to which "group" owns a file.

A 10 character display indicates the status of permissions. Reading the first character from the left, a d denotes a directory and a minus sign denotes a file. The illustration at right denotes a directory; this example, -rxxr-xr-x, denotes a file.

Access rights are symbolized in this manner:

r indicates read permission, one may read or copy a file

w indicates write permission, one may change a file

x indicates execution permission, one may execute a file

For example in the illustration at right:

The violet section, called "Owner," describes a directory with read, write, and execution permission. The owner may do absolutely anything that they please with this directory. It is "unprotected."

The green section, called "Group," denotes read and execute permission for the group. The group may "read" or look at the file or directory, and run any of it's programs by "executing." However, no one from the group can erase the file accidentally by saving over top of the owner's original file -- it is "write protected."

The red section, called "World," denotes read and execute permission for the users exterior to the owner and group. Again, imagine Internet users seeking the ability to execute your html, flash/shockwave, sound and image files. In this case, the "world" can't erase the directory accidentally by saving over top of the owner's original directory. However, the world may "read" or look at the directory, and execute.

Our class should be able to read and execute peer files. Do not allow your peers to write over your files. The UNIX command for changing permission to read and execute only is:

chmod 755 filename

or

chmod 755 directoryname

You may also use the Fetch interface (as noted in the illustration above) to change the permissions on files that you are uploading to your gl accounts. Always double-check permissions in an UNIX shell by typing ls -l before moving on.

  gag