Monday, August 18, 2008

Slackware 12.0 - CUPS network printer

Here's how CUPS worked-out on a couple different systems connected to a wired ethernet LAN, with a printer attached to the same LAN, and wifi access to the Web on each box (dual-homed boxes).

slackware 12.0 - huge.s kernel patched for non-smp
500 MHz PIII
500 MB Ram
HP1100 LaserJet
Netgear PS 101 MiniServer
Linksys BEFSR41 10/100 router
RTL8139 type card

What works: install

For most of us, the CUPS webtool at  http://localhost:631
simply never works. Not only this, but it waits until the final step in a timely 6-part process to note the failure. For me, it feels more efficient to add printers manually. Perhaps some day all the permissions will align with the stars and CUPS will work. At any rate, there is no limit to the number of printers we can manually add to our workstation.

Lpadmin is the command, but first prepare the printspace:
  • add print group ("lp", in many cases) to the groups for users I want to have print access. Users who are not in lp or whatever, can notprint or cancel print jobs without rooting-up.
  • decide which ppd to use with the printer.
With these two accomplished, try to add the printer:
# lpadmin -p HP1100 -E -v socket:// -m hpijs.ppd
This may return the error that the hpijs ppd file, in this case hpijs.ppd, cannot be copied. Ppd's need to be in the correct format (uncompressed ppd) and directory (/usr/share/cups/model) if lpadmin is to find them and add them.

Foomatic hides and zips their ppds. I finally located them in /usr/share/cups/model/foomatic-ppds/HP. The one I needed was HP-LaserJet1100.ppd.gz. I copied this file into /usr/share/cups/model , unzipped it: "gzip -d HP*", and renamed it hp1100.ppd for ease of loading. Then I ran:
# lpadmin -p HP1100 -E -v socket:// -m hp1100.ppd
The printer was successfully added to the system. Suppose, however, I wanted to try several .ppd files to determine the one with the clearest print and functionality? Ppd files can easily be added and deleted. Simply copy the new .ppd file (let's call this new one eg, another.ppd) into /usr/share/cups/model/ and run:
# lpadmin -p HP1100 -P another.ppd

What works: configuration

Ideally again, one should be able to use the CUPS webtool at  http://localhost:631 for configuration, just as we were supposed to be able to add printers with it. If the web interface is working, use it. If not part two of our work will be to modify the file /etc/cups/printers.conf with the right settings and restart the CUPS server so it reads the file. In /etc/cups/printers.conf one line has different possible structures depending on how the printer is attached. Let's say we've named our device "printername", some possibilities are:
DeviceURI socket://ip.address/printername #LAN
DeviceURI socket://ip.address:ps101name #LAN version2
DeviceURI parallel:/dev/lp0 #parallel port
DeviceURI usb:/dev/usb/lp0 #usb port

I experimented until I determined the correct one for the physical connection which, in my case, was on a LAN. I looked in my router and found my printserver received DHCP at
I navigated there ( in Firefox, and found a GUI interface which allowed me to rename the printserver to any name I desired, but decided to leave it PS101. Accordingly, the successful syntax for my DeviceURI was this one:
DeviceURI socket://
and my final working configuration file went like this:
# Printer configuration file for CUPS v1.3.7
# Written by cupsd on 2008-12-01 04:19
<DefaultPrinter HP1100>
Info HP1100
DeviceURI socket://
State Idle
StateTime 1228132708
Accepting Yes
Shared Yes
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
OpPolicy default
ErrorPolicy stop-printer

After all this, I ran
# service restart cups
in order for CUPS to re-read the /etc/cups/printers.conf file with the new information. I was able to print from all programs.

test prints

While testing printer ppd's, I ran a lot of test prints. Some worked, but the ones that didn't print piled-up in the queue, and the CUPS interface at http://localhost:631 would never allow me to delete jobs. CLI solution to delete print jobs, (assuming CUPS is running, there is no "lpstat" w/out CUPS):
# lpstat -o
provides pending print jobs and the job number eg, "HP1100-1". Then
# cancel HP1100-1
will get rid of the job. Run "lpstat -o" again to verify, if you like.
# lpstat -v [list of installed printers]
# lpstat -d [names default printer, also can specify using this]

xfce4 note

To print from Mousepad and others that use X-settings, xfce printing needs to recognize the CUPS printer. Try printing in Mousepad and see if the CUPS printer is available. If not, configuring xfce4 to CUPS will be necessary. This was simple for me. I simply went to the XFCE menu, then access Settings ->Settings Manager -> Printing System. Once in Printing System, I selected the CUPS network printer and closed the menu. I then opened a Mouspad file to print; sure enough, the CUPS printer appeared in my options.

What is supposed to work (as opposed to all of the above)

First, good CUPS documentation here.
Essentially, one should be able to navigate to CUPS at  http://localhost:631 with Firefox and add printers, manage the print queue, or do other config changes. I never could get the parts to sync enough to add a printer, let alone administer them. Some considerations:
  • GUI authentication: CUPS apparently relies on PAM, Slackware does not provide PAM?
  • parallel: HPLIP is supposedly needed for support if using a parallel port, but not for network printer. I could not get HPLIP to see the parallel port on the legacy system
  • parallel: snmp might be a factor
In the name of gleaning understanding and advancing progress from previously attempted approaches or, at least, of not duplicating effort,here were some initial directions:
1. configure network and verify dhcp assigned print server and slackbox IP's. Let's call these IP's as follows: - Print Server - Slackbox

2. check /etc/rc.d/ - verify rc.cups (and rc.hplip, if it were needed) are 755.
3. is printer plugged in? PS101 plugged in?
4. Firefox to http://912.168.1.101. Blue admin page. Change or leave the name of the PS101, but be sure to write it down - you will need it later in your /etc/cups/printers.conf file. Print a test page to see that the server is talking to the printer properly.
5. Firefox to http://localhost:631 CUPS admin interface. Make sure it comes up.
6. Check that tcp and udp ports 161,162, and 9100 are not locked-down.

CUPS Webtool notes http://localhost:631

1. Try adding the printer with the CUPS webtool. It likely will wait until the (frustratingly) last step in the process and reject your password. Since CUPS uses PAM for password authentication and Slackware doesn't use PAM, I made many many many attempts at editing the /etc/cups/cupsd.conf file to eliminate the password requirement, but it always prompted me for a password in the CUPS webtool. According to the information at this slack site here is how one should proceed:
A. Lets say your name is "doofus" and you declared your SystemGroup in cupsd.conf as "wheel":
lppasswd -g wheel -a doofus
B. Check to be certain:
# cat /etc/cups/passwd.md5 doofus:wheel:01234567890abcde1234567890abcde12
C. Now restart CUPS and go back to the webtool in Firefox and add the printer:
#/etc/rc.d/rc.cups restart
I never got it to work; the password was always rejected and I could never add a printer.


SNMP (Simple Network Management Protocol) is a powerful process originally designed to simplify web management. Many processes take advantage of SNMP functionality and one of them is HPLIP

If hp-setup doesn't work, then the road may be long. Try using SNMP to determine if the kernel can see the printer at the nework address:
snmpwalk -Os -c public -v 1 ip.address.of.printer
Per this site HP tshoot, the response should be something which shows the manufacturer,or SNMP may not be installed correctly. This means working with the /etc/snmp/snmpd.conf file.

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