[plug] How to clean out the printer spool

[Craig Ringer]

>>sometimes I want to stop printing before a document has finished, or as 
>>recently, the printer(a HP Deskjet 500) was printing a long doc and the 
>>screensaver came on and the printing stopped(aborted it said)  How did this 
>>happen?
> 
> Sounds strange to me, that the screensaver did in fact stop the printing
> job...

Extremely so. It could've slowed it down if the screensaver wasn't 
runing nice()d and was eating cpu time /and/ the printing process was 
somehow cpu-intensive. Even then, it doesn't make much sense.

OOM caused by the screensaver? It's insane, but as close to possible as 
I can think of. You'd probably need a machine with 16mb or at most 32mb 
of RAM for that though.

>>I needed to empty the spool to stop pages of ? Postscript stuff coming out 
>>when the printer is switched back on  How do I do this?
>>
>>I use RH9. I don't know how to locate "lpd".  I thought it was 
>>"/var/spool/lp<printername>" (it's not)  Also, I tried to shutdown lpd with 
>>"/etc/rc.d/init.d/lpd stop" which failed  "line195: kill : 2529 operation 
>>not permitted".
> 
> Not permitted sounds like you have to do that as root...

Yup.

>>Process 2529 is lpd.  Coukd I kill it from"ps -aux" If so, how do I restart 
>>lpd?

No need to kill it manually and restart it, just do
	/etd/init.d/lpd restart

That said, since you're running red hat 9, if you have some time to 
fiddle you might want to try installing CUPS to replace lpd. It's a 
/much/ better printing system, and is now standard on most modern linux 
distros. I seem to remember that RH may be dropping support for lprng 
(lpd) in their next release.

CUPS has open source drivers for the HP printers which HP actively works 
on. It's only inkjets, but still good to know that they're out there and 
helping out.

http://hpinkjet.sourceforge.net/

I find the CUPS generic DeskJet driver works well with most HP DeskJets. 
If yours supports PostScript natively, you can just use the ppd supplied 
with it as the driver in CUPS :-) . If not, the drivers built into cups 
do a good job for HP-PCL printers.

CUPS has a web-based config interface on port 631 (http://localhost:631) 
where you can add/remove printers, cancel jobs, send test pages, etc. 
Very handy. I'm using CUPS at work to control a big Xerox workgroup 
printer, an older HP-4MV, an Okidata dot matrix for _legacy_ apps, and a 
DeskJet in our accountant's office. All totally transparent and fuss 
free. Many apps (KDE, OpenOffice, etc) integrate with CUPS and talk to 
it to get data about printers, etc.

> There is the command lpq to see what is in the queue and lprm to remove
> a job from the print queue.

Sometimes print systems implement 'lpstat' as well.

> % lprm -PHP5L 500

or 'cancel hp5l-500' in SysV printing systems.