Creating Smart Print Queues
After adding a new queue in /etc/printcap, you will need to tell the print daemon to reread the printcap file. Listing 7 is a script I wrote years ago to take care of the additional work necessary to activate your new printcap entries. You may want to verify the path names to the various directories and commands for your system. You must run it as superuser.
What if you do not always have a printer attached or available, but you wanted to send something to the print queue for printing at a later time? Will the job wait until you attach the printer or connect to the network? Yes, it will if your raw printer is attached to your parallel port because /dev/lp waits for handshake signals from the printer.
If jobs fail to print, you need to determine if the problem lies with the print system or your filter. The first place to look is in your system log file, /var/log/messages, then look in the log file for the queue. Next, carefully check the syntax in your printcap file. Make sure each line except the last one for each entry ends in a “\”. Turn on some debugging output to check the operation of your filter. If the problem is with the print system, you can try to stop and restart printing. You should have a script in your system startup area that does this properly. In the SuSE distribution, the startup and shutdown script is /sbin/init.d/lpd. As with any System V-style boot script, this may be manually run as /sbin/init.d/lpd start or /sbin/init.d/lpd stop.
A print queue can get stuck when the spool directory's disk gets full. This can happen for a very large job or if your disk partition is too small. You will have to remove the job with lprm to free it up, then clean up unnecessary files on that disk partition or move your spool directories to a larger partition. After copying all the directories and files to a new location, you can remove all the old directories (rm -r lpd) and replace the lpd directory with a symbolic link to the new location where you have copied the old lpd directory tree (ln -s /path/to/new/location/lpd /var/spool/lpd).
We discussed how BSD printing works and some of the common options in the printcap configuration file. We showed you how to write a filter for altering the file that is sent to the actual printer and how to write a filter that automatically processes different types of input files for printing. We also learned that a filter can redirect the output to different devices or files. Hopefully, this will give you enough information to understand and create your own “smart” printer queues and simplify your printing tasks.
Mark Plimley (email@example.com) started home-computing in 1978 with an Imsai 8080 (8-bit, 2MHz Intel 8080). In his former life as a mechanical engineer, he programmed in FORTRAN. He has been employed mainly as a UNIX systems administrator since 1992 and has been using Linux since January, 1995. When not in front of a computer screen, he can be found tinkering around the house, doing some activity with his wife and two teenagers or helping out at church.
All listings referred to in this article are available by anonymous download in the file ftp.linuxjournal.com/pub/lj/listings/issue73/3741.tgz.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
- Parsing an RSS News Feed with a Bash Script
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This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide