Web Conference 2004 Writing Perl/CGI Scripts for ITS/ASET Web services Penn State News, and Server Specific Info

Updated Dec 26, 2008

What does Penn State provide?

The Applied Information Technology (AIT) group currently in Consulting and Support Services (CSS) (formerly in Academic Services and Emerging Technologies (ASET)), a unit of Information Technology Services (ITS) provide various Web services for the Penn State community including Penn State's home (http://www.psu.edu/), the Penn State Personal server (http://www.personal.psu.edu/), the technology behind the Student Organizations Web service (http://www.clubs.psu.edu/), a Web service for courses (http://www.courses.psu.edu/), various Departmental Web sites and virtually hosted domains, and countless other Web services. Among other features, we provide CGI service for those who need it, and a test CGI service on http://test.scripts.psu.edu/.

How are ITS/CSS Web services at Penn State unique?

Every Web server can be configured differently, and run many different types of Web server software and extentions. ITS/CSS, charged with running some central Web services for Penn State, including http://www.psu.edu/, has made some decisions on how our services run. Here are the chief differences that separate it from others.

• We run Unix

  Specifically most general purpose ITS/CSS Web servers run IBM's AIX operating system on RS/6000 based hardware, some on the Sun Solaris operating system on Sun Sparc hardware and others on GNU/Linux on Intel hardware. While known for its stability and ease of administration, there are sometimes small snags when working with other platforms (ie, Windows) such as UNIX line endings for text files and filename case sensitivity

• We run Apache

  The Apache Web server, which has been reported to run over 65% of Web servers on the Internet and climbing, is our choice of Web server software. One of the benefits to running Apache is it allows us to allow Web content editors to control some aspects of the server configuration via .htaccess files.

  Specifically, we run the 1.3.x series versions of Apache. As powerful as the Apache 2.0 series is, 1.3 is so stable and useful we have not yet found a truely compelling reason to upgrade (think Ford model T).

  See the Apache 1.3.x documentation.

• We store content in Kerberos/LDAP integrated GPFS, the system used for PASS

  The Distributed Computing Environment and Distributed File System (DCE/DFS) was our system for storing content used on the Web and controlling access to our services at the time this tutorial was originally writen. Since then, the Penn State Access Account Storage Space (PASS), has undergone a major technology upgrade (see alert-740) to standard MIT-brand Kerberos, Lightweight Directory Access Protocol (LDAP) based group information and authorization registry and General Parallel File System (GPFS).

  DCE/DFS ran on Unix and presented Unix based permissions to tools that understand it, such as SSH Secure File Transfer. However, DCE/DFS also had a rich Access Control List permissions system, which often interacted with Unix based permissions in unintuitive ways.

  GPFS also runs on UNIX, interacts with traditional UNIX mode permissions, and has an even richer Access Control List permission scheme (actually 2). However, to prevent UNIX mode interaction from accidentally deleting ACL permissions, users and their programs can no longer change permissions via the traditional UNIX mode permission interfaces (attempts to try will be ignored and return no error). Instead permissions must be changed via a proper ACL interface. PASS makes use of the Network File System (NFS) version 4 style ACL in GPFS as opposed to the "POSIX" style ACL available which is a bit more similar to DFS. Programs familiar with the traditional UNIX mode permissions can still read an approximate mode. Penn State plans to work with the GPFS vendor to develop a method for the traditional UNIX mode permission interface to change ACL permissions in the future.

  Unlike DFS, the Web-based Access Control List permission management tool (known as "ACL Explorer" and "PASS File Permissions Manager") for GPFS presents a simplified version of the ACL. To take full advantage of all features of the NFSv4 style ACL available in GPFS, one has to use a native NFSv4 client today. There may be a more advanced ACL Explorer in the future. For now, the current ACL Explorer for GPFS should provide sufficient capabilities for most users, including installing CGI scripts.

  The PASS system is a centralized system of files that can be accessed by many Web servers and many different upload methods. This increases its utility.

• We use separate servers for "testing" and "production" service

  The http://test.scripts.psu.edu/ server is our "test" server. You may run any code you want there, provided you follow applicable policies such as AD-20. The idea is you test your code here before asking it to be installed on a production service. This looks like the Personal server, http://www.personal.psu.edu/ in its URI layout; for instance user xyz123 may have personal Webspace at http://www.personal.psu.edu/users/x/y/xyz123/ which is also visible at the URL http://test.scripts.psu.edu/users/x/y/xyz123/. You may also run "production" code here long term if you wish, but you do so without any guarantee the server will be online. As others are testing their code here, it is possible for a bug in a CGI to take down the server or cause other problems. That's why we have a test server.

  The servers your sites run from are "production" in that we typically do not allow CGI to run unless we install it for you.

What's new with Penn State Web services?

This section remains current to original time of writing (dated for tutorial given June 14-15, 2004).

• New name for the CGI test server, test.scripts.psu.edu - formerly was scripts.cac.psu.edu

• Improved ACL Explorer interface and documentation - Web based tool for changing permissions in PASS (DCE/DFS) (available via https://www.work.psu.edu/)

• New guestbook / CGI procedure documents - for installing other people's CGI code

• COMING SOON - PHP / ASP / JSP dynamic Web content engines and database access - first stage: http://php.scripts.psu.edu/ (sans database) to go online this month

If you have any questions, feel free to ask me - mailto:jcd@psu.edu

Content by: Jeff D'Angelo <jcd@psu.edu> © 2004

Last update on: Sunday, 28-Dec-2008 20:10:50 EST