3.2 The UNIX Printers

NOTE: There has been some confusion in the past as to where paper is located and how to acquire it. Paper is kept in 102. If that supply is running low, send mail to labadmin@ccs.neu.edu. If there is a dire need for paper and the Lab Admin can not deliver it in time, then go down to the Systems Office (310 WVH) and ask for some paper for the labs.

There are several commands to be used on the printers:

lpr -Preiniger file is the standard command for printing a file to reiniger.
lpq -Preiniger is used for viewing the jobs currently in Escher's print queue waiting to print.
lpc stop reiniger will stop Escher from printing any more jobs without flushing the queue.
lpc start reiniger will start Escher printing again.
lprm -Preiniger 15 will remove job #15 from Escher's print queue.
lpc move reiniger 15 renoir will move job #15 from Escher's queue to Renoir's.

Anywhere that the word 'escher' is used in the previous commands, you can also use 'renoir' to run on that printer's queue instead. Also, job #15 is just an example, these can be run on any job in the queue at the time.

The job number can be found by running the lpq -Preiniger command:

Printer: reiniger@mordor  'HP800N located in 102 WVH'
 Queue: 1 printable job
 Server: pid 14349 active
 Unspooler: pid 14351 active
 Status: printing 'ddonahue@algorab+72' starting OF 'ifhp' at 17:41:22.144
 Filter_status: (of) getting sync using 'pjl echo' at 17:41:22.384
 Rank   Owner/ID                  Class Job Files                 Size Time
active ddonahue@algorab+72          A    72 (stdin)              15031 17:41:21

As you can see here, the following information is available:

Printer Name: reiniger
Print Server Name: mordor
Printer Type and Location: HP800N located in 102WVH
Number of printable jobs: 1
Printer's Current Status: printing
The Owner of Each Job: ddonahue
The Machine from Which it was Printed: algorab
The Job Number: 72
The Time it Started Printing: 17:41:22.144
The Size of the Job in Bytes: 15031

With all of this information, it should be relatively easy to find out which job may be jamming in the printer and perhaps why (maybe it's a huge graphic file and it takes a long time to be processed). Tracking down unwanted print jobs and removing them is now much easier than it was before. As always, if there are any questions, email lab-admin.

3.3 UNIX Network

The UNIX machines at the College are linked in a complex network environment. Home directories are kept on a large file server, so a user sees the same directory no matter which machines they log on to. Particular machines are also used as mail servers, software servers, print servers, and so on. Further complicating things, our local area network is broken up into a number of subnets, and some servers limit their services to certain subnets.

If a particular server computer goes down, or becomes slow due to heavy use or software problems, users may notice problems on their workstations. The workstation may become slow, or some program may hang, or the workstation may freeze altogether. Diagnosing network problems is complex, and the proctors can help us by noticing and reporting details of the networks behavior.

When a problem occurs, wait a couple of minutes and see if it goes away; a server may simply be overwhelmed with requests. If a problem persists more than a few minutes, try to send mail to systems. Always note machine names, error messages, the username of the person having problems, and any other information that might be useful. Open the console icon on the workstation having problems to check for error messages. Walk around the lab to see if groups of machines are experiencing problems. It can sometimes be useful for us to know that all the decs, but none of the suns, are having a problem, for example.

The more detailed your messages are, the more helpful they are likely to be. Tell us if escher is jammed; but if you check the print queue (lpq -Pescher and notice it has been jamming when a particular job is printing, your mail may be more helpful. Debugging networks involves noticing coincidences. Learn to use UNIX commands like ps- aux|more to see what programs are running on a machine, and df to see how full the disks are.

3.4 Closing the UNIX Lab