Chapter 16: Printing remotely over TCP/IP

Table of contents

• Chapter 16: Printing remotely over TCP/IP
  • How RLP works
  • The client/server model
  • Installing and removing RLP
    • Manually adding remote printers
  • Deleting printcap entries
  • Setting up a client
  • Setting up a print server
  • Using RLP
    • 4.3BSD clients
    • SCO clients
  • For more about remote line printing

Chapter 16

Printing remotely over TCP/IP

• Printer classes are not supported.

• Not all line printer command options are supported on the client.

• Log in to the print server at the console.

• Log in to the print server from another machine using terminal emulation.

• Issue printer administration commands from another machine using the rcmd(TC) command.

RLP operates differently from normal printing. First, a new file, called printcap(SFF),

contains information about local and remote printers and related files needed by the print commands. Second, the usual SCO system print commands (lp, cancel, and lpstat) are moved to the directory /usr/lpd/remote for safekeeping, and new versions of these commands are moved to /usr/bin. These new commands consult the file /etc/printcap to determine whether the print job is going to a local printer or a remote printer attached to a print server.

If the printer is local, printing occurs just as it would with the standard command. All standard command options are supported. This is because the new command simply invokes the standard command, now located in /usr/lpd/remote. If the printer is remote, the command spools the print job and invokes the lpd daemon. This daemon packages the print job in 4.3BSD format and sends it over the network to the host specified in the /etc/printcap file.

The client/server model

The systems that send print jobs are called clients. The systems that directly control the printers are called print servers. Clients and print servers can be either an SCO system or a 4.3BSD system (or one of its derivatives, such as SunOS^(TM)).

See also:

• ``Setting up a print server''

• ``Setting up a client''

Before installing RLP on your SCO system, be sure first to install TCP/IP. To install RLP:

1. Log in as root.

2. Enter:
   
   mkdev rlp

   You now see the following display:
   

      	Remote printing configuration
      
   
      Do you want to install or delete remote printing (i/d/q)?
   

3. You have three options:

   • To install or reinstall RLP, enter i. Skip to the next step.

   • To remove RLP after it has been installed, enter d. Once RLP has been removed, your local printing environment is restored and you are returned to the shell prompt.

   • To quit and return to the shell prompt, enter q.
   
   

4. You now see the following messages:

      Installing Remote Line Printing
      
   
      Creating directories /usr/lpd/remote and /usr/spool/lpd and file /etc/printcap
      Saving lp, cancel, lpmove and lpstat commands to /usr/lpd/local
      Installing remote lp, cancel, lpmove and lpstat commands 
      Do you wish to change the remote printer description file /etc/printcap (y/n)?
   

   To define printers available through RLP, enter y. The rlpconf command is then executed. See ``Setting up a client'' and ``Setting up a print server'' later in this chapter for information on rlpconf.

   To wait until later to define printers, enter n. You then see the message:

      Run /etc/rlpconf to change the remote printer description file
   

   Remember to run rlpconf at some point before using RLP. Otherwise, you will have no entries in the /etc/printcap file.

5. If the directories that RLP needs to do the installation already exist, you see the following message:

      Remote line printing working directory already exists.
      
   
      Do you wish to continue installing the remote line printing system (y/n)?
   

   Enter y to continue the installation. Enter n to stop and return to the shell prompt.

6. You are now asked the following question:

      Do you want to start remote daemon now (y/n)?
   

   To start the lpd(ADMN) daemon, enter y. This daemon must be running for RLP to work. To wait until later to start the daemon, enter n.
   

To configure a remote printer, execute the rlpconf command. For more information, refer to the rlpconf(ADMN) manual page. This command edits the /etc/printcap file for you. The following example illustrates the use of rlpconf to set up the sunlaser printer to produce an entry in the /etc/printcap file like the one shown at the beginning of this section. Assuming you are logged in as root, invoke the rlpconf command. You see output similar to the following:

   		Remote Printing Configuration
   

   Enter information for remote printers or local printers accepting
   remote printing requests
   

   Please enter the printer name (q to quit): sunlaser
   

   Is sunlaser a remote printer or a local printer (r/l)? r
   

   Please enter the name of the remote host that sunlaser is 
   attached to: ohio
   

   	Printer sunlaser is attached to host ohio
   

   Is this correct? (y/n) y
   

   If 'ohio' currently runs SCO OpenServer Release 5 or above,
   it can support the extended remote line printer protocol.
   Do you want to turn on the "extended RLP protocol" support flag?
   

   If you're not sure, answer 'n'? (y/n) [n]
   

   

   Would you like this to be the system default printer? (y/n) y
   

   Make sure that your host name appears in ohio's /etc/hosts.equiv
   or /etc/hosts.lpd file.
   Make sure that sunlaser appears in ohio's /etc/printcap file (BSD format)
   Make sure that sunlaser has a spool directory on ohio
   Putting sunlaser in printer description file and creating spool dir
   Updating LP information...done
   Updating /usr/spool/lp/default...done

The above example shows how to configure your client to use a remote printer called sunlaser attached to the print server ohio. After entering the name of the printer and the print server, you must verify the information just entered. If it is correct, enter y. If it is not, enter n, at which point you are asked if you want to try again. Answer y to be prompted again for the name of the printer and the print server. Answer n to exit and return to the shell prompt.

Continuing with the above example, you are asked if you wish to make the printer the system default. Answer y or n. If you answer n, users on the client that wish to route a print job to sunlaser must do so explicitly by using the -d option in the lp command.

Following this query, you are advised to verify certain things on the print server. The rlpconf command now checks that the printer is not already
listed in /etc/printcap. If it is, a message to that effect is displayed. If it is not, the printer information is added to /etc/printcap.

In addition, the spool directory for the printer, in this case /usr/spool/lpd/sunlaser, is created and configuration information indicating the name of the printer and the print server is stored in a file called configuration. This file is located in a subdirectory bearing the printer's name under /usr/spool/lp/admins/lp/printers. In this example, the pathname of the file is /usr/spool/lp/admins/lp/printers/sunlaser/configuration. Finally, if the printer is to be the system default, the file /usr/spool/lp/default is updated to contain the name of the printer.

Once you have configured the printer, the screen clears and you see output similar to the following:

   		Remote Printing Configuration
   

   Enter information for remote printers or local printers accepting
   print jobs.
   

   Please enter the printer name (q to quit): q

Once you have finished configuring printers, ensure that the RLP daemon lpd is running. You can do this by entering the command ps -fe and verifying that the daemon appears in the listing.

See also:

• ``The client/server model''

To delete an entry in the /etc/printcap file, you must use your favorite text editor. Be sure to delete the entire entry, which is continued over two lines. Also, you should delete the spool directory /usr/spool/lpd/printer_name and the file /usr/spool/lp/admins/lp/printers/printer_name/configuration associated with the deleted printer. Finally, if the deleted printer is the system default printer, you should modify the file /usr/spool/lp/default appropriately. See ``Setting up a client'' earlier in this chapter for more information.

Setting up a client

The printer description file /etc/printcap on the client machine provides routing and other information about printers.

For a full description of the /etc/printcap file format, see the printcap(SFF) manual page.

Here is an example of an entry in the /etc/printcap file, followed by an explanation of each field. Note that fields are separated by colons.

   laser::lp=:rm=ohio:rp=sunlaser:sd=/usr/spool/lpd/laser

• The first field, laser, is the name by which the client knows the printer. For a remote printer, the name that the client uses need not be the same as that used by the print server. In this example, laser is an alias for the printer named sunlaser on ohio.

• The second field (before the first colon on the second line) is empty by default. When used, it defines the name of the error log file.

• The third field, starting with lp=, must be empty (that is, followed immediately by a colon) for remote printing. This field specifies the device name for a local printer.

• The fourth field, starting with rm=, specifies the network name of the print server. In this example, the print server is called ohio.
  

• The fifth field, starting with rp=, specifies the name that the print server uses for the printer.

• The last field, starting with sd=, is the name of the spooling directory on the client. It is in this directory that print jobs are stored before being sent over the network to the print server. This directory is always located in /usr/spool/lpd and bears the name of the printer. In this example, the spool directory is called /usr/spool/lpd/laser.

See also:

• ``The client/server model''

To set up a print server to process RLP requests, do the following:

• Ensure that the RLP daemon lpd is running. You can do this by entering the command ps -fe and verifying that the daemon appears in the listing.

• Ensure that that all printers attached to the print server are working properly as local printers. See the documentation that accompanies the operating system running on the print server for information on how to set up local printer services.

• List all of the clients that are to have access to the print server in either the /etc/hosts.equiv or the /etc/hosts.lpd file using your favorite text editor.
  
  Listing a client in the latter file is more secure, in that only remote printer access is granted to the specified client. See the manual page that describes /etc/hosts.equiv for information on the kind of access made available to hosts listed in that file.

• Execute rlpconf to create the /etc/printcap file and the spool directories for printers attached to the print server.

   		Remote Printing Configuration
   

   Enter information for remote printers or local printers accepting
   print jobs.
   

   Please enter the printer name (q to quit): sunlaser
   

   Is sunlaser a remote printer or a local printer (r/l)? l
   

   Please enter the name of the device for sunlaser: /dev/laser
   

   	Printer sunlaser uses device /dev/laser
   

   Is this correct? (y/n) y
   

   Putting sunlaser in printer description file and creating spool
   directory...done

Once you indicate that the device filename is correct, the rlpconf command checks that the printer is not already listed in /etc/printcap. If it is, a message to that effect is displayed. Otherwise, the printer information is added to the /etc/printcap file and the spool directory for the printer, /usr/spool/lpd/sunlaser, is created.

Once processing is complete for one printer, you are prompted to set up another printer. When you are done, enter q to exit rlpconf and return to the shell prompt.

See also:

• ``The client/server model''

To use RLP, you invoke one of the supported commands. There are actually two sets of commands: one for SCO clients and one for 4.3BSD clients and derivatives.

4.3BSD clients

On 4.3BSD clients and derivatives, use the standard printing commands lpr, lprm, and lpq to do remote printing. The following options are supported when sending a print job to a remote printer attached to an SCO system on which RLP has been installed:

lpr -Pprinter_name [-#number_of_copies] [-Ttitle] [-s]

(The -s option uses symbolic links instead of copying the file to the spool directory.)

lpq -Pprinter_name
lprm -Pprinter_name
lprm -Pprinter_name job_number

Only the options listed previously are supported for the lpr, lpq, and lprm commands when used for remote printing. If unsupported options are specified, they are ignored by the print server and the print job is submitted without them.

If printing is to be done locally, all of the options that are normally available for local printing are supported.

SCO clients

On SCO clients, the RLP commands are lp, lpmove, cancel, and lpstat. These commands work just like their non-RLP counterparts when invoked with no options and when invoked with the following supported options:

lp -dprinter_name

lp -nnumber_of_copies

lp -ttitle_to_print_on_banner

lp -irequest_id_options

modify an earlier print request of a job still in the local queue.

lp -qpriority_level

lp -L spooler|local|live=<device>

local or spooled printing

lp -T file_type

type of input files

lp -o length=scaled_number

page length

lp -o width=scaled_number

page width

lp -o lpi=scaled_number

line pitch

lp -o cpi=scaled_number

character pitch

lp -o stty='stty_options'

port characteristics

lp -o other_local_options

as defined locally

lp -o nofilebreak

no inter-file form feed

lp -o nobanner

no banner page

lp -m | -w

mail/write when done

lp -H hold

hold -- do not print until notified. The print job will remain on the spool on the local machine instead of going to the remote printer. Other print requests will go ahead of a held request until it is resumed.

lp -H immediate

print the request next. The printer will attempt to print the job at queue priority one.

lp -H resume

resume a previously held request.

lp -c

make copies first

lp -r

use no filter

lp -R

remove after spooling

lp -s

no request-id message

lpstat -aremote_printer_name

acceptance status

lpstat -oremote_printer_name

output requests status

lpstat -premote_printer_name

available printers and printer status

lpstat -p list -D

give printer description

lpstat -vremote_printer_name

pathnames of associated devices

lpstat -c classes

show available classes

lpstat -u users

show status of user requests

lpstat -f forms

show available forms

lpstat -S char_sets,print_wheels

show available fonts

lpstat -d

show default destination

lpstat -l

verbose mode

lpstat -r

show status of spooler

lpstat -s

show summary status

lpstat -t

show status of everything

The variable ``all'' is allowed with the -a, -c, -f, -o, -p, -S, -u, -v options for lpstat.

Only the options listed above are supported for the lp and lpstat commands when used for remote printing. If one or more unsupported options are specified, they are ignored and the print job is submitted without them. If printing is to be done locally, all of the options that are normally available for local printing are supported.

See the cancel(C), lp(C), lpmove(ADM), and lpstat(C) manual pages for more information on the supported options.

For more about remote line printing

To get more information about the line printer daemon protocol, see the following Request for Comments (RFC). For information on how to obtain RFCs, see ``Obtaining RFCs from the Internet''.

 --------------------------------------------------------------------
 RFC    Title
 --------------------------------------------------------------------
 1179   Line Printer Daemon Protocol