Debugging Printing Problems

Introduction

This is a short description of how to debug printing problems with -Samba. This describes how to debug problems with printing from a SMB -client to a Samba server, not the other way around. For the reverse -see the examples/printing directory.

Ok, so you want to print to a Samba server from your PC. The first -thing you need to understand is that Samba does not actually do any -printing itself, it just acts as a middleman between your PC client -and your Unix printing subsystem. Samba receives the file from the PC -then passes the file to a external "print command". What print command -you use is up to you.

The whole things is controlled using options in smb.conf. The most -relevant options (which you should look up in the smb.conf man page) -are:

      [global]
-        print command     - send a file to a spooler
-        lpq command       - get spool queue status
-        lprm command      - remove a job
-      [printers]
-        path = /var/spool/lpd/samba

The following are nice to know about:

        queuepause command   - stop a printer or print queue
-        queueresume command  - start a printer or print queue

Example:

        print command = /usr/bin/lpr -r -P%p %s
-        lpq command   = /usr/bin/lpq    -P%p %s
-        lprm command  = /usr/bin/lprm   -P%p %j
-        queuepause command = /usr/sbin/lpc -P%p stop
-        queuepause command = /usr/sbin/lpc -P%p start

Samba should set reasonable defaults for these depending on your -system type, but it isn't clairvoyant. It is not uncommon that you -have to tweak these for local conditions. The commands should -always have fully specified pathnames, as the smdb may not have -the correct PATH values.

When you send a job to Samba to be printed, it will make a temporary -copy of it in the directory specified in the [printers] section. -and it should be periodically cleaned out. The lpr -r option -requests that the temporary copy be removed after printing; If -printing fails then you might find leftover files in this directory, -and it should be periodically cleaned out. Samba used the lpq -command to determine the "job number" assigned to your print job -by the spooler.

The %>letter< are "macros" that get dynamically replaced with appropriate -values when they are used. The %s gets replaced with the name of the spool -file that Samba creates and the %p gets replaced with the name of the -printer. The %j gets replaced with the "job number" which comes from -the lpq output.

Debugging printer problems

One way to debug printing problems is to start by replacing these -command with shell scripts that record the arguments and the contents -of the print file. A simple example of this kind of things might -be:

	print command = /tmp/saveprint %p %s
-
-    #!/bin/saveprint
-    # we make sure that we are the right user
-    /usr/bin/id -p >/tmp/tmp.print
-    # we run the command and save the error messages
-    # replace the command with the one appropriate for your system
-    /usr/bin/lpr -r -P$1 $2 2>>&/tmp/tmp.print

Then you print a file and try removing it. You may find that the -print queue needs to be stopped in order to see the queue status -and remove the job:

h4: {42} % echo hi >/tmp/hi
-h4: {43} % smbclient //localhost/lw4
-added interface ip=10.0.0.4 bcast=10.0.0.255 nmask=255.255.255.0
-Password: 
-Domain=[ASTART] OS=[Unix] Server=[Samba 2.0.7]
-smb: \> print /tmp/hi
-putting file /tmp/hi as hi-17534 (0.0 kb/s) (average 0.0 kb/s)
-smb: \> queue
-1049     3            hi-17534
-smb: \> cancel 1049
-Error cancelling job 1049 : code 0
-smb: \> cancel 1049
-Job 1049 cancelled
-smb: \> queue
-smb: \> exit

The 'code 0' indicates that the job was removed. The comment -by the smbclient is a bit misleading on this. -You can observe the command output and then and look at the -/tmp/tmp.print file to see what the results are. You can quickly -find out if the problem is with your printing system. Often people -have problems with their /etc/printcap file or permissions on -various print queues.

What printers do I have?

You can use the 'testprns' program to check to see if the printer -name you are using is recognized by Samba. For example, you can -use:

    testprns printer /etc/printcap

Samba can get its printcap information from a file or from a program. -You can try the following to see the format of the extracted -information:

    testprns -a printer /etc/printcap
-
-    testprns -a printer '|/bin/cat printcap'

Setting up printcap and print servers

You may need to set up some printcaps for your Samba system to use. -It is strongly recommended that you use the facilities provided by -the print spooler to set up queues and printcap information.

Samba requires either a printcap or program to deliver printcap -information. This printcap information has the format:

  name|alias1|alias2...:option=value:...

For almost all printing systems, the printer 'name' must be composed -only of alphanumeric or underscore '_' characters. Some systems also -allow hyphens ('-') as well. An alias is an alternative name for the -printer, and an alias with a space in it is used as a 'comment' -about the printer. The printcap format optionally uses a \ at the end of lines -to extend the printcap to multiple lines.

Here are some examples of printcap files:

pr just printer name
pr|alias printer name and alias
pr|My Printer printer name, alias used as comment
pr:sh:\ Same as pr:sh:cm= testing - :cm= \ - testing
pr:sh Same as pr:sh:cm= testing - :cm= testing

Samba reads the printcap information when first started. If you make -changes in the printcap information, then you must do the following:

make sure that the print spooler is aware of these changes. -The LPRng system uses the 'lpc reread' command to do this.
make sure that the spool queues, etc., exist and have the -correct permissions. The LPRng system uses the 'checkpc -f' -command to do this.
You now should send a SIGHUP signal to the smbd server to have -it reread the printcap information.

Job sent, no output

This is the most frustrating part of printing. You may have sent the -job, verified that the job was forwarded, set up a wrapper around -the command to send the file, but there was no output from the printer.

First, check to make sure that the job REALLY is getting to the -right print queue. If you are using a BSD or LPRng print spooler, -you can temporarily stop the printing of jobs. Jobs can still be -submitted, but they will not be printed. Use:

  lpc -Pprinter stop

Now submit a print job and then use 'lpq -Pprinter' to see if the -job is in the print queue. If it is not in the print queue then -you will have to find out why it is not being accepted for printing.

Next, you may want to check to see what the format of the job really -was. With the assistance of the system administrator you can view -the submitted jobs files. You may be surprised to find that these -are not in what you would expect to call a printable format. -You can use the UNIX 'file' utitily to determine what the job -format actually is:

    cd /var/spool/lpd/printer   # spool directory of print jobs
-    ls                          # find job files
-    file dfA001myhost

You should make sure that your printer supports this format OR that -your system administrator has installed a 'print filter' that will -convert the file to a format appropriate for your printer.

Job sent, strange output

Once you have the job printing, you can then start worrying about -making it print nicely.

The most common problem is extra pages of output: banner pages -OR blank pages at the end.

If you are getting banner pages, check and make sure that the -printcap option or printer option is configured for no banners. -If you have a printcap, this is the :sh (suppress header or banner -page) option. You should have the following in your printer.

   printer: ... :sh

If you have this option and are still getting banner pages, there -is a strong chance that your printer is generating them for you -automatically. You should make sure that banner printing is disabled -for the printer. This usually requires using the printer setup software -or procedures supplied by the printer manufacturer.

If you get an extra page of output, this could be due to problems -with your job format, or if you are generating PostScript jobs, -incorrect setting on your printer driver on the MicroSoft client. -For example, under Win95 there is a option:

  Printers|Printer Name|(Right Click)Properties|Postscript|Advanced|

that allows you to choose if a Ctrl-D is appended to all jobs. -This is a very bad thing to do, as most spooling systems will -automatically add a ^D to the end of the job if it is detected as -PostScript. The multiple ^D may cause an additional page of output.

Raw PostScript printed

This is a problem that is usually caused by either the print spooling -system putting information at the start of the print job that makes -the printer think the job is a text file, or your printer simply -does not support PostScript. You may need to enable 'Automatic -Format Detection' on your printer.

Advanced Printing

Note that you can do some pretty magic things by using your -imagination with the "print command" option and some shell scripts. -Doing print accounting is easy by passing the %U option to a print -command shell script. You could even make the print command detect -the type of output and its size and send it to an appropriate -printer.

Real debugging

If the above debug tips don't help, then maybe you need to bring in -the bug guns, system tracing. See Tracing.txt in this directory.