Transcript Kein Folientitel - HEPiX Services at CASPUR

Network printing in
heterogenous environments
Christoph Beyer
[email protected]
Deutsches Elektronen Synchrotron,
IT
Notkestr. 85
22607 Hamburg, Germany
Printing at DESY

~300 printer and ~400 queues

2 E250 running SOLARIS 2.7 with 1GB memory each as
server

~250.000 jobs per month

No MAC and Novell support defacto

2 administrators

LPRng 3.6.26 (slidely patched) and IFHP 3.4.4
The perfect system

Printserver should understand every protocol the clients
speak

Access to printers should be restricted, every job must go
through the central spooler, this gives every job a fair chance
to be printed

The system should be robust, in case of server failures jobs
should be redirected to a working machine

Additional features like accounting, format conversion,
loadbalancing and filtering should be possible

Administration and update of clients and servers should be
as painless as possible
The perfect architecture
NET
WARE
UNIX
MAC
LPR
WINDOWS
Apple
Talk
SMB
NETWARE
NETWARE
client
SERVER
LPR
Central Printserver
LPR
Remote printer
TCP
HP jetdirect printer
Solution (obvious)
Take advantage of the flexibility of UNIX as a
backend for queuing jobs and talking to the
printer.
Use software to present the UNIX queues to the
clients using their native protocols.
That's all !!!
The Berkley printserver architecture
(see RFC1179 for the 'nitty gritty details')
Job file
'/etc/printcap'
Spooling client
LPR
Server
LPD
Mngmnt clients
LPQ
LPRM
LPC
Server
LPD
/var/spool/lpd/pr1
Datafile
dfA001host
Controlfile
cfA001host
Started at boottime
Printer
(target)
Pr2
Printer
(target) Pr1
'/etc/lpd.conf'
'/etc/lpd.perms'
(LPRng only)
Controlfile content
ASCII printable characters, line ending with \n
Example:
Hpcx1839.desy.de
Pchbeyer
J(stdin)
CA
Lchbeyer
fdfA458pcx1839.desy.de
N(stdin)
UdfA458pcx1839.desy.de
Host name
User name (banner)
Job title
Job class
User name (billing)
Data file
Data file name
Unlink data file
LPRng the next generation Berkeley spooler

An enhanced, extended and portable
implementation of the Berkeley lpr print spooler
functionality.

While providing the same interface and meeting
RFC 1179 requirements, the implementation is
completely independent

Compiles and runs on a wide variety of UNIX
systems, and is compatible with other print spoolers

LPRng supports Kerberos 5 for authentication

Complexity comes with functionality
Nice LPRng features

On UNIX clients the ':rm=<spoola>,<spoolb>:\' entry is a
great built in failover feature

Stand alone printing using 'lpr -P<printer>@<host>' or eaven
'lpr -P<port>@<printer>'

Very nice 'lpc' features (is not mentioned in RFC1179): topq,
hold, redirect queues, set status message, reread conf files,
redirect jobs

Great debugging by simply typing 'lpq -L -P<printer>',
different debugging levels in addition

4 ascii files (printcap, lpd.conf, lpd.perms, ifhp.conf) make the
only difference to any other workgroupserver in your network

Localy attached printers can be defined in a second printcap
Nice LPRng features (ct'd)

Provides SysV and BSD binaries for all UNIX platforms

Is compatible to all known printing implementations eaven to
those who violate the RFC1179 while being as close at the
RFC1179 as possible

The permission file 'lpd.perms' allows different access to the
functions of 'lpr', 'lpq', 'lprm', 'lpc' for classes of users

Global definitions in the 'lpd.conf' file greatly simplify
management and printcap

Very good documentation for LPRng and IFHP

Good support on the mailing list

Accounting per page and printer
What is a filter ?

Is typically run on the server to convert the data files
into the printer specific language, to create
bannerpages (bp) or to query the printer (of)

Is called by the lpd daemon, reads from <STDIN> writes
to <STDOUT>

Is invoked by printcap entry: :if=<path to your filter>:\
for special formats, refering to the controlfile content:
:<index>f:<path to your filter>:\

In LPRng: :filter=<path to your filter>:\
generally defined for all formats
The IFHP filter package

Enhanced, extended, highly configurable and portable
implementation of a print filter for use with LPRng.

Supports network, serial and parallel printers

Page accounting and job recovery possible

Supports text, PostScript, PCL and PJL printer

Very strong file type detection due to the additional use of the
file tool

Over 500 printer models types and configurations are
supported

The config file makes configuration and implementation of
new printers or features / formats extremely easy and flexible
Connecting the printer
(Possible network communication protocols)

RFC1179 BSD or TCP/IP
supported by most if not all printers with TCP/IP interface, the
only status information exchanged is success or failure of the
transfer. Used typically for transport between client and spooler,
default no filtering, transfered just like a set of files!

Socket protocol (TCP/IP)
bidirectional connection to the internal printengine, error and
status conditions are reported over the connection. PJL and PS
status requests can be sent to the printer. Typical for connecting
HP printers on port 9100.

Appsocket protocol (TCP/IP)
two ports are used a TCP/IP listening port and a UDP query port.
Typically used by Tectronics Phaser series and QMS printers.
Printer specific languages

PostScript is a stack based programming language,
developed mainly by ADOBE in the 70's
-
comes in different versions (level 1-3)
must be compiled/interpreted by the printengines, which
always have bugs
requires a huge amount of memory on the printer, is very
slow otherwise
everybody uses it because the code for the interpreter was sold
by ADOBE for a very low price (higher now, so we see some
interesting imitations)
very portable over different vendors printers and nearly generic
previewer can give you an exact idea of what your code will
look like
standard and most portable way to generate documents for
printing
+
+
+
+
Printer specific languages (ct'd)

PrinterControlLanguage (PCL) developed by Hewlett
Packard in the 80's it grew from a simple escape code control
language to a fully developed PDL.
-
old printers do not have font download support
due to the heavy use of control characters (ESC) PCL files
are not easy to edit or view
there is no real standard, the documentation is very poor
+
+
simple to generate
much faster because there is not much to do for the
printengine
What is PJL ?

PrinterJobLanguage (PJL) developed by Hewlett Packard to
gain control over whole printjobs not just individual files in a
print job.

Works as a wrapper for each job (if the printer supports it).
The sequence 'ESC%-12345X' is heavily used by PJL.
Whenever it appears the current language interpreter is
interrupted and hands over control to PJL.

The most common use of PJL is for language switching at the
beginning of a printjob.

There is a standard set of error messages provided by PJL as
well, unfortunately not all printers support all PJL features and
manufactures are very quiet about the sets of PJL messages
their printers support.
UNIX clients

To gain full functionality (job querying and removing) using
LPRng on the server, LPRng must run on the clients as well!
-
You have to provide mechanisms for installation and compiled
binaries
+
+
+
+
+
+
The architecture and behaviour is similar on all clients
Both BSD and SysV style binaries are available on all machines
Very good debugging (lot of built in functions)
Very easy and scalable update mechanism with 'checkpc' tool
Built in failover with ':rm=<spool1>,<spool2>:\' entry in printcap
Local attached printers can be supported without editing the
distributed printcap
You get rid of complicated and stupid native implementations
(e.g. Solaris)
+
The native Windows printing architecture

Printserver installs minimal driver information on client
('add printer' button)

Client gets printerdefinition from server via RPC for each
printjob (early binding)

Since NT 4.0 TCP/IP printing to UNIX server is possible if the
LPR package is installed
Windows integration methods

job forwarding from the NT spooler
+automatic driver installation through NT spooler
+printer information is held in one central place, changes
take effect immediately (RPC)
- no job control, because NT spooler doesn't forward querys

TCP/IP printing on the NT client
+job control over the known NT GUIs (if you use LPRng for
Windows)
- need to be local administrator on client to 'add printer'
- no automatic driver installation
- once installed the driver never gets changed, big problems
if printer hardware or tray specififcation changes etc.
What about SAMBA ?

Extremely reliable and stable print and fileserver under UNIX
for Windows clients, current release is 2.0.7

Remote client driver installation is possible in the latest
release, but it's kind of very tricky

You need to be local admin on the client to add a printer

RPC's are not supported, full driver installation on the clients

Print service is very stable and easy to administrate, job
control and removement over the native Windows GUI's

RPC support and enhanced driver installation features are
realised in the next release (2.2)
Windows printing at DESY
Desktop
Driver installation,
RPC support,
printjob transfer via SMB
Windows printserver
LPR
Lpq / lprm using
GUI for LPRng for Windows
Remote printer
Central Printserver (UNIX)
LPR
TCP
Remote printer
DESY printing tool (screenshot)
Strategies for large sites

Printer panels must be locked, host access lists and IP adress over
bootp

Only a small number of printserver is running a lpd daemon, all
clients send their jobs directly to them. Every printer should be
known on every server (failover)

Use NIS / LDAP to distribute printcap or don't use a printcap at all
but a default spooler (lpd.conf entry)

On UNIX clients the ':rm=<spoola>,<spoolb>:\' entry is a great built
in failover feature, all other clients should print on a nameserver
alias which can be changed in case of server downtimes

IFHP can be configured to send mails to operators on certain traps
(for ex: paper out, toner low etc.)
Some useful stuff

http://www.lprng.com For LPRng and IFHP

Patched 3.6.26 version:
http://www.desy.de/dtg/printing/download.html

HPNP, a snmp tool to query and configure jetdirectinterfaces
at:
http://www.hp.com

NPADMIN, a very nice tool to query and administrate any kind of
printer:
http://npadmin.sourceforge.net/

Adobe Systems Inc: Postscript Language tutorial and Cookbook
Addison-wesley

Network Printing by T. Rademacher & M. Gast
O'Reilly