9.10 Samba

Samba is a free software solution to the problem of making Unix filesystems available to Windows operating systems. Windows NT uses a system of network file sharing based on their own SMB (Server message block) protocol. Samba is a Unix daemon-based service which makes Unix disks visible to Windows NT. Samba maps usernames, so to use Samba we need an account with the same name on the NT server and on the Unix server. It maps usernames textually, without much security. Samba configuration is in Unix style, by editing the text-file /etc/smb.conf. Here is an example file. Note carefully the ‘hosts allow’ line which restricts access to disks to specific IP addresses, like TCP wrappers.

[global] printing = bsd

printcap name = /etc/printcap load printers = yes

guest account = nobody invalid users = root workgroup = UNIX hosts allow = 128.39.

[homes]

comment = Home Directories browseable = no

read only = no create mode = 0644

[printers]

comment = All Printers browseable = no

path = /tmp printable = yes public = no writable = no create mode = 0644

Once the Samba server is active, the disks are available for use with the net use command, e.g.

C:\> net use F: \\host\directory

This example maps the named directory on the named host to NT drive letter F:. The reverse problem of mounting NT filesystems on a Unix host works only for GNU/Linux hosts at present:

gnulinux% smbmount //nthost/directory /mountpoint -U administrator

9.11 The printer service

Printing services vary from single printers coupled to private workstations to huge consolidated spooling services serving large organizations [329, 251].

Host print services need to be told about available printers by registering the printers in a local database. In BSD-like print servers this database is kept in a flat file called /etc/printcap. In System V print servers, a program called lpadmin is used to register printers and it’s anyone’s guess what happens to that information.

The way in which we register printers thus depends on

•What kind of operating system we are using

•Whether we are running any special network printer software.

The main difference is between BSD-like systems and System V. Recently a replacement print service was introduced for a generic heterogeneous network. Called LPRng, this package preserves the simplicity of the BSD system while providing superior functionality to both [243]. Another alternative is the Common Unix Printing System (CUPS).

In order to register a printer with a BSD-like printer service, we do the following:

•Think of a name for the printer.

•Decide whether it is going to be connected directly to a host or stand alone on the network.

•Register the printer with the printing system so that the daemons which provide the print service know how to talk to it. This can include manually making a ‘spool’ directory for its queue files. This normally lies under var/spool or /usr/spool.

mkdir /var/spool/ printer-name

•Most Unix systems assume the existence of a default printer which is referred to by the name ‘lp’. If you do not specify a particular printer when printing, your data are sent to the default printer. It is up to us to name or alias one of our printers ‘lp’. Each printer may have several names or aliases.

With some print spoolers, we also need to decide whether to send all data to a common central server, or whether to let each host handle its own negotiations for printing. If we are interested in maintaining a record of how many pages each user has printed, then a centralized solution is a much simpler option. The downside of this is that, if there is a large user base, the traffic might present a considerable load for one host. A central print spooler must have sufficient disk space to temporarily store all the incoming print jobs.

9.11.1CUPS/LPRng

The Common Unix Print System (CUPS) has emerged in the last few years as the favored printing solution on many desktops. It reads information from traditional Unix format files.