General

  • There is one course per project.
  • The project_head is the primary instructor
  • Anybody with group_root permission is assumed to be a TA
  1. Instructors and TA's are allowed to sudo to any student on the ops node

Instructors may sudo to a TA but not conversely.

Code changes:

The instacct utility (described below) has a function which generates an include file for sudo which is copied to the ops node and installed as /usr/local/etc/sudoers.classes. The function is run either by explicit request on the command line, or as a side-effect when students are assigned to a class, and at the end of the semester when a class is wiped.

  1. Experiment Permissions

When an experiment is created in the default group, only the student's home directory and /proj/<PID>/exp/<EID> are exported to the nodes in the experiment.

If the experiment is created in a subgroup of the main project, normal export permissions already isolate students from others (except for those in the group). /proj directory exports are applied as above.

The ssh public keys of the instructor and TA's are put into the root .ssh/authorized_keys file so that the instructors can log into any node to grade the experiment (as class exercise) or debug it.

Code changes: tmcd

  1. Web Interface

Instructors and TA's are allowed to Freeze, Thaw and SU-as a student and edit a student's profile. When an instructor removes a class account from the project, instead of actually removing it, it recycles the account.

Code changes:

www/user_defs.php defines new routines InstructedBy() and CourseAcct(), referenced in delete_user.php3 moduserinfo.php3 showuser.php3 suuser.php3. There are perl versions of these in db/User.pm.in.

  1. Recyclable student accounts

Student accounts are not created in the normal manner (create an account, apply to join an existing project) - instead:

A stem is chosen for the project, say in the case of the project USC558L, sc558, and then a number of accounts are generated of the form sc558[a-z][a-z] as many are need to accommodate the students in the class.

The instructor provides a list of email address, and one account is assigned per email address.

At the end of the semester, the student accounts are wiped - all experiments headed by the student are terminated, all files underneath the students home directory are deleted, the passwords changed to something random, all public ssh keys and ssl certs recorded in the database are flushed and then randomly regenerated as in a new account.

Code changes:

The source for the instacct utility was added to the tree as

testbed/account/instacct.in, manage_class.in

The separate perl script manage_class gets installed on the ops node to invoke an sslxmlrpc call so that instructors may do almost anything that a testbed adminstrator could do.

The two commands reserved to admins are to set the stem for class names, and to generate a number of accounts in advance that are ready to assign - in the same state a previously used and wiped account as in.

Since our funders require us to provide usage goals and metrics, we track the number of student accounts which were generated, (re-)assigned and wiped by means of a couple of additional tables in the database:

project_history and project_attributes.

  1. Other peculiarities of student accounts

Student accounts may not join other projects.

A student may be taking more than one course and only have one (student) email address; we added a couple of warts to deal with this -

There is an ancillary table in the database called email_aliases; and when the account is assigned the .forward is set to this and the students email becomes e.g. sc558ab@…

So, for all users, students or not, we require web login by uid only and not email address.

Code changes:

account/tbacct.in was changed so that when it generates a .forward file, the email_aliases entry preempts the usr_email in the users table.

An unresolved bug is letting an instructor correct a students email, now that it is kept in a separate place.

Last modified 10 years ago Last modified on Sep 29, 2011 5:40:59 PM