couple of questions regarding printing on Linux, pls

From Sony Lloyd

Answered By Ben Okopnik, Heather Stern, Kapil Hari Paranjape

Sorry to distrurb

[Ben] Do not disturb sleeping dragons, for you are crunchy and good with ketchup. This is The Answer Gang - we _like being "disturbed" (several of us here could be described as having that attribute permanently set...) - at least if you pose an interesting question. So, fear not but approach our saurine majesties, small human creature.

(Anybody seen that BBQ sauce bottle?)

[Heather] No, but I think I saw a pizza heading into the hoard room.

I would have couple of questions regarding printing on Linux, pls: (1) I see "lpd" loading at my system boot up, but my kernel is not compiled with support for "lp" (confirmed by absence of "lp" from outputs of "cat /proc/devices").

[Ben] "/proc/devices" does not necessarily reflect whether you have parallel port support available or not; in fact, mine does not contain an "lp" entry after startup, and yet I can happily print via my parallel port. The thing that makes the difference (and loads the modules as necessary) is the "kmod" option in the kernel: my "lp" module will be automatically loaded whenever I need it. Until then, "/proc/devices" will not have it listed.

How come lpd loads without linux being set for printing + with lp ports not detected by linux?

[Ben] "lpd" is a piece of software that "catches" and outputs print jobs; that's all it does. If it is linked in your "/etc/rc*d" directories, it will load on startup. It does not care whether you've set up a parallel port or not; it just does what it's been told to do, which is start. If you have not configured the system corectly, and try to _use "lpd", it will log an error message - just as it should.

One of the major differences between Wind0ws and Unix is that, rather than large monolithic programs that do many things at once (the Wind0ws way), Unix uses "small sharp tools" - programs that do one thing well and can be easily connected to other programs. In this philosophy, a printing daemon does not (and should not) check for the presence or absence of ports on startup - that's not its job. What if, for example, I decide not to load the "lp" module until I want to print? Should "lpd" fail to load?

(2)I have an old linux 2.0.30 with no xwindow.

[Ben] The 2.0 kernels are perfectly capable of supporting XFree86. In fact, that's a bit of a misnomer: X only has a tangential relationship with the kernel - there's nothing in the kernel (as far as I know, anyway) that is required specifically for running it.

[Heather] Yes, there is; the feature is called "sockets". But, if you disable it there are a lot of things that won't work.

Depending on how much your monitor hates you, you might need framebuffers, and that's a newer kernel feature.

[Kapil] Actually, inter-process-communication was required for X to first be ported to Linux. In other words Linux pre-ipcs (in the old version 0.12 days possibly upto version 0.98?) could not run X.

[Ben] True, but then you may as well say that if you had no kernel, you couldn't run X either... 2.0.x is way after that. In practice, if you have a $GENERIC_KERNEL, X will work just fine.

Simply want to set it to pint to a canon bjc80 printer via parrallel port. I did recompiled the kernel for "lp" support, but do not know what to do next.

[Ben] Well, the thing to do _first would have been reading the Printing-HOWTO (and perhaps the Printing-Usage-HOWTO) at <http://www.tldp.org/>;. It's always a good idea to look for a HOWTO when you are experimenting with a new and unfamiliar Linux subsystem.

For now, the lp ports is not detected yetby my linux system.

[Ben] You don't really know that, actually. One way you can tell - it's a little subtle, actually - is by using the "file" utility and its "-s" (special file) option. The messages will vary a bit depending on whether the printing daemon is loaded or not.

# Starting with printing daemon loaded
ben@Fenrir:~$ file -s /dev/lp0
/dev/lp0: can't read `/dev/lp0' (Device or resource busy).
ben@Fenrir:~$ file -s /dev/lp1
/dev/lp1: can't read `/dev/lp1' (No such device or address).

See the difference? Here it is with the daemon stopped:

ben@Fenrir:~$ su -c '/etc/init.d/cupsys stop'
Password:
Stopping CUPSys: cupsd.
ben@Fenrir:~$ file -s /dev/lp0
/dev/lp0: file: read failed (Input/output error).
ben@Fenrir:~$ file -s /dev/lp1
/dev/lp1: can't read `/dev/lp1' (No such device or address).

Different message, but still understandable.

So how to manually (step by step, with no x window utility -- simply from command line) configure my printer.

[Ben] Read the above HOWTOs; they'll walk you through the process. Feel free to let us know if you run into any problems you can't solve.

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