The Structure of the LP Print Service (System Administration Guide: Advanced Administration)

System Administration Guide: Advanced Administration

The Structure of the LP Print Service

This section describes the directory structure, files, logs, and commands of the LP print service.

LP Print Service Directories

The files of the LP print service are distributed among seven directories, as shown in the following table.

Table 8–1 Directories for the LP Print Service


Directory	Contents
`/usr/bin`	The LP print service user commands
`/etc/lp`	A hierarchy of LP server configuration files
`/usr/share/lib`	The `terminfo` database directory
`/usr/lib/print`	The lp conversion scripts, `in.lpd` daemon and the `printd` daemon. The `printd` daemon transfers all pending jobs in the`/var/spool/print` directory once per minute. When there are no jobs remaining to transfer, it exits
`/usr/sbin`	The LP print service administrative commands
`/usr/lib/lp`	The LP daemons; directories for binary files and PostScript filters; and the `model` directory (which contains the standard printer interface program)
`/var/lp/logs`	The logs for LP activities: `lpsched.n –` Messages from `lpsched` and `requests.n` – Information about completed print requests
`/var/spool/lp`	The spooling directory where files are queued for printing
`/var/spool/print`	The LP print service client-side request staging area

LP Print Service Configuration Files

The scheduler stores configuration information in LP configuration files located in the /etc/lp directory, as described in the following table.

Caution –

The configuration files listed in this table are private interfaces, and are subject to change in future releases. You should not build software that relies on these files being in their current locations or that relies on the data being in the format currently used.

Table 8–2 Contents of the /etc/lp Directory


File	Type	Description
`classes`	Directory	Files identifying classes provided by the `lpadmin -c` command.
`fd`	Directory	Description of existing filters.
`filter.table`	File	Print filter lookup table.
`forms`	Directory	Location to put files for each form. Initially, this directory is empty.
`interfaces`	Directory	Printer interface program files.
`logs`	Link to `/var/lp/logs`	Log files of printing activities.
`model`	Link to `/usr/lib/lp/model`	The standard printer interface program.
`printers`	Directory	Directories for each local printer. Each directory contains configuration information and alert files for an individual printer.
`pwheels`	Directory	Print wheel or cartridge files.

These configuration files serve a similar function to the /etc/printcap file on lpd-based print servers.

Note –

You can check the contents of the configuration files, but you should not edit them directly. Instead, use the lpadmin command to make configuration changes. Your changes will be written to the configuration files in the /etc/lp directory. The lpsched daemon administers and updates the configuration files.

The /etc/lp/printers directory has a subdirectory for each local printer known to the system. The following example shows the /etc/lp/printers subdirectories of printers sparc1 and luna.

$ ls -l /etc/lp/printers
drwxrwxr-x 2 lp lp 512 Jan 23 23:53 luna
drwxrwxr-x 2 lp lp 512 Jan 11 17:50 sparc1

The following table describes the files within each of the printer-specific directories.

File Name	Description
`alert.sh`	Shell to execute in response to alerts
`alert.vars`	Alert variables
`configuration`	Configuration file
`users.deny`	List of users to whom printer access is denied
`comment`	Printer description

The configuration file for the printer luna, /etc/lp/printers/luna/configuration, would typically appear as follows:

Banner: on: Always
Content types: PS
Device: /dev/term/b
Interface: /usr/lib/lp/model/standard
Printer type: PS
Modules: default

The `terminfo` Database

The /usr/share/lib directory contains the terminfo database directory, which contains definitions for many types of terminals and printers. The LP print service uses information in the terminfo database to initialize a printer, to establish a selected page size, character pitch, line pitch, and character set, as well as to communicate the sequence of codes to a printer.

Each printer is identified in the terminfo database with a short name. For a description of the structure of the terminfo database, see Printer Type. If necessary, you can add entries to the terminfo database, but it is a tedious and time-consuming process. For more information, see Adding a terminfo Entry for an Unsupported Printer.

Daemons and LP Internal Files

The /usr/lib/lp directory contains daemons and files used by the LP print service, as described in the following table.

Table 8–3 Contents of the /usr/lib/lp Directory


File	Type	Description
`bin`	Directory	Contains files for generating printing alerts, slow filters, and queue management programs.
`lpsched`	Daemon	Manages scheduling of LP print requests.
`model`	Directory	Contains the standard printer interface program.
`postscript`	Directory	Contains all PostScript filter programs provided by the LP print service. These filters come with descriptor files in the `/etc/lp/fd` directory that tell the LP print service the characteristics of the filters and where to locate them.

LP Print Service Log Files

The LP print service maintains two sets of log files described in the following table.

Log File Name	Description
syslogd(1M)	Set `lpr.debug` in `/etc/syslog.conf` to enable LP print service logging
`/var/spool/lp`	A list of current requests that are in the print queue
`/var/lp/logs/requests`	An ongoing history of print requests

Print Queue Logs

The scheduler for each system keeps a log of print requests in the directories /var/spool/lp/tmp/system and /var/spool/lp/requests/system. Each print request has two files (one in each directory) that contain information about the request. The information in the /var/spool/lp/requests/system directory can be accessed only by root or lp. The information in the /var/spool/lp/tmp/system can be accessed only by the user who submitted the request, root, or lp.

The following example shows the contents of the /var/spool/lp/tmp/starbug directory:

$ ls /var/spool/lp/tmp/starbug
5     5-0
# cat 5-0
C 1
D print1
F /etc/profile
P 20
T /etc/profile
t simple
U root
s 0000
v 2

These files remain in their directories only as long as the print request is in the queue. Once the request is finished, the information in the files is combined and appended to the /var/lp/logs/requests file, which is described in the section that follows.

Use the information in the /var/spool/lp/logs directory if you need to track the status of a print request that is currently in the queue.

History Logs

The LP print service records a history of printing services in two log files: lpsched and requests. These log files are located in the /var/lp/logs directory. You can use the information in these logs to diagnose and troubleshoot printing problems. This is an example of the contents of the /var/lp/logs directory:

# cd /var/lp/logs
# ls
lpsched.1    requests    requests.2
lpsched      lpsched.2   requests.1
#

The two most important log files for troubleshooting is the lpsched log, which contains information about local printing requests and the requests log, which contains information about print requests that are completed and no longer in the print queue.

The requests log has a simple structure, so that you can extract data using common UNIX shell commands. Requests are listed in the order they are printed, and are separated by lines showing their request IDs. Each line below the separator line, the line that starts with =, is marked with a single letter that identifies the kind of information contained in that line. Each letter is separated from the data by a single space.

The following example shows the contents of a requests log:

# pwd
/var/lp/logs
# tail requests.2
= print1-3, uid 0, gid 1, size 206662, Wed Nov 14 08:56:30 MST 2001
z print1
C 1
D print1
F /usr/dict/words
P 20
T /usr/dict/words
t simple
U root
s 0x0014
v 2
#

The following table shows the letter codes and the content of their corresponding lines in the LP requests log.

Table 8–4 Letter Codes in the LP requests Log


Letter	Content of Line
`=`	The separator line. It contains the following items: request ID, user ID (UID), and group IDs (GIDs) of the user, the total number of bytes in the original (unfiltered) file size, and the time when the request was queued.
`z`	The name of the printer.
`C`	The number of copies printed.
`D`	The printer or class destination or the word `any`.
`F`	The name of the file printed. The line is repeated for each file printed. Files were printed in the order shown.
`f`	(Optional) The name of the form used.
`H`	(Optional) One of three types of special handling: resume, hold, and immediate.
`N`	(Optional) The type of alert used when the print request was successfully completed. The type is the letter `M` if the user was notified by email or `W` if the user was notified by a message to the terminal.
`O`	(Optional) The printer-dependent `-o` options (for example, nobanner).
`P`	The priority of the print request.
`p`	The list of pages printed.
`r`	(Optional) A single-letter line that is included if the user asked for “raw” processing of the files (the `lp -r` command).
`S`	(Optional) The character set, print wheel, or cartridge used.
`T`	The title placed on the banner page.
`t`	The type of content found in the files.
`U`	The name of the user who submitted the print request.
`s`	The outcome of the request, shown as a combination of individual bits expressed in hexadecimal form. Several bits are used internally by the print service. The bits and what they mean are describe in the table that follows this one.
`x`	(Optional) The slow filter used for the print request.
`Y`	(Optional) The list of special modes for the print filters used to print the request.
`z`	(Optional) The printer used for the request. This printer differs from the destination (the `D` line) if the request was queued for any printer or a class of printers, or if the request was moved to another destination.

The following table shows the outcome codes in the LP requests log and their descriptions.

Table 8–5 Outcome Codes in the LP requests Log


Outcome Code	Description
`0x0001`	The request was held pending resume.
`0x0002`	Slow filtering is running.
`0x0004`	Slow filtering finished successfully.
`0x0008`	The request is on the printer.
`0x0010`	Printing finished successfully.
`0x0020`	The request was held pending user change.
`0x0040`	The request was canceled.
`0x0080`	The request will print next.
`0x0100`	The request failed filtering or printing.
`0x0200`	The request is in transit to a remote printer. (obsolete)
`0x0400`	The user will be notified.
`0x0800`	A notification is running.
`0x1000`	A remote system has accepted the request. (obsolete)
`0x2000`	The administrator placed a hold on the request.
`0x4000`	The printer had to change filters.
`0x8000`	The request is temporarily stopped.

Spooling Directories

Files queued for printing are stored in the /var/spool/lp directory until they are printed, which might be only seconds. The following table shows the contents of the /var/spool/lp directory.

Table 8–6 Contents of the /var/spool/lp Directory


File	Type	Description
`SCHEDLOCK`	File	Lock file for the scheduler. Check for this file if the scheduler dies and will not restart.
`admins`	Directory	Link to `/etc/lp.`
`bin`	Directory	Link to `/usr/lib/lp/bin.`
`logs`	Link	Link to `../lp/logs` where completed print requests are logged.
`model`	Link	Link to `/usr/lib/lp/model.`
`requests`	Directory	Directory that contains subdirectories for each configured printer where print requests are logged until printed. Users cannot access this log.
`system`	Directory	A print status file for the system.
`temp`	Link	Link to `/var/spool/lp/tmp/hostname`, which contains the spooled requests.
`tmp`	Directory	Directory for each configured printer where print requests are logged until printed. Changes to existing print requests are also recorded in this log.