Computing Info for Ling 645/CMSC 723, Fall 1997

Computing Info for Ling 645/CMSC 723, Fall 1997
Introduction to Computational Linguistics

The aITs Unix cluster

The aITs Unix cluster systems (details below) share a common file system, common news and mail systems, and common users. This means users can login to whichever of the systems they want and their same login id and password will work and their files will be available. This also means users can do their own "load balancing" by logging in to whichever system seems to be best for them at the time.

System Details

The cluster machines are as follows:
          Alpha Systems

All mail sent to the cluster should be addressed to (which is the address that is placed on all outgoing cluster mail). Mail sent in this manner can be read from any cluster system. The machine known as is also part of the cluster but acts as a server for the cluster. DO NOT USE UMD5 for anything other than your EMAIL address. Never login to umd5. Games, IRC, and MUDs are not allowed on the aITs Unix cluster. The home directories contain default .login, .cshrc, and .logout files. In addition, the access mode on the home directories has been set to 700. This means that a student will not be able to copy files from an unsuspecting student, unless the owner changes the mode of his home directory to something that allows such access. Of course students can still MAIL things to each other. User files are NFS mounted on various servers. Symbolic links are used to create the file names found in the system password file. This means the names returned by the pwd command may not match the names found in the system password file. Users should always refer to home directories by the ~loginid or $HOME methods.


All students should read the University of Maryland Guidelines for the Acceptable Use of Computing Resources and the AITS Computer Use Guidelines.

System Access

The only access to the aITs Unix systems is via the campus network. WAM (Workstations At Maryland) workstations, such as those located in CSS room 3330, are directly connected to the campus network. Directions for using WAM workstations can be found in each workstation laboratory and in the aITs Information Technology Library (CSS West Wing room 1400).


Academic Information Technology Services provides First-Aid and general consulting services to those who use Unix computing systems on campus. aITs Unix machines run the Ultrix version of Unix. With the realization that there are other versions of Unix being used on campus, First-Aid and the aITs Help Desk will address questions based on their experience with the aITs Unix systems. Students should use the First-Aid service (located in all WAM workstation laboratories). They may also use the First-Aid Hotline for phone-in questions ((301) 405-6941), which is answered by First-Aiders in the PGII WAM lab. Exact hours of service are posted at each First-Aid station. The aITs Information Technology Library (CSS West Wing room 1400) has reference copies of Unix manuals and documentation. The Library also sells "Introduction to the aITs UNIX Systems" (aITs Unix handout number 1).


Academic Information Technology Services uses the Usenet news system on its Unix systems to inform users about system outages, new software, etc. The news group is used for all news items. Items that are considered of interest to the general University community are also placed in the um.general news group. The default .login file contains a call to the readnews program. On some systems, users prefer to use the rn program to read news. If rn is used, the call to readnews should be removed from the users' .login file.


aITs has replaced the stock lpr program with a shell script that calls MDQS to print a file on prl, which is the 3800 laser printer attached to the campus UMDD IBM system. The call is
lpr <file>
to initiate printing. Output may be retrieved at the aITs dispatch counter on the first floor of the CSS building.

File Recovery

A dump of all files is taken every week. These file backups are for recovery from catastrophic loss. Individual user file recovery is not available at this time.


Unix systems do not have the concept of an account manager; this means that if a user forgets his password, aITs must change it for the user. Requests for change of password should be made to Ira Gold at the address above. Requests to change student passwords will only be honored when they are made by the instructor. Instructors can make such requests via electronic mail. Requests must include login id and may include a suggested new password.

Disk Quota

All user login ids on the aITs Unix systems have a disk quota associated with them. When the disk quota is exceeded, the user will not be able to create new files until the amount of disk space in use has been reduced, or the disk quota has been increased. Requests for change of disk quota should be made to Ira Gold at the address above. Requests to change student disk quotas will only be honored when they are made by the instructor. Instructors can make such requests via electronic mail. Requests must include login id, desired new disk quota (expressed in megabytes), and system name. In all cases, requests for higher disk quotas will be evaluated against system resources and system load.

/tmp and /var/tmp

/tmp is a small directory used by system utilities for short term scratch files. Users should not place their files in /tmp. User files should be placed in user directories (every user has one) or /var/tmp (again, short term storage). Files residing in /tmp and /var/tmp can be deleted without notice if disk space becomes critical. See "Disk Quota" above for information about requesting disk quota changes. /tmp and /var/tmp are local to each system in the cluster.


The cluster file /usr/local/doc/cluster contains cluster details, including a table showing software availability. Please read this file for full cluster details.
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