ManagingTaylor UUCPLinux Network Administrators GuidePrevNextChapter 16. ManagingTaylor UUCPTable of ContentsUUCP Transfers and Remote ExecutionUUCP Configuration FilesControlling Access to UUCP FeaturesSetting Up Your System for Dialing InUUCP Low-Level ProtocolsTroubleshootingLog Files and DebuggingUUCP was designed in the late seventies by Mike Lesk at AT&T Bell
Laboratories to provide a simple dialup network over public telephone
lines. Despite the popularity of dialup PPP and SLIP connections to the
Internet, many people who want to have email and Usenet News on their home
machine still use UUCP because it is often cheaper, especially in countries
where Internet users have to pay by the minute for local telephone calls, or
where they do not have a local ISP and must pay long distance toll rates to
connect. Although there are many implementations of UUCP running on a wide
variety of hardware platforms and operating systems, overall, they are highly
compatible.However, as with most software that has somehow become “standard”
over the years, there is no UUCP that one would call the
UUCP. It has undergone a steady evolution since the first version was
implemented in 1976. Currently, there are two major species that differ
mainly in their hardware support and configuration. Of these two,
various implementations exist, each varying slightly from its siblings.One species is known as Version 2 UUCP, which dates back to a 1977
implementation by Mike Lesk, David A. Novitz, and Greg Chesson. Although it
is fairly old, it is still frequently used. Recent implementations of
Version 2 provide much of the comfort that the newer UUCP species do.The second species was developed in 1983 and is commonly referred to
as BNU (Basic Networking Utilities) or HoneyDanBer UUCP. The latter
name is derived from the authors' names (P. Honeyman, D. A. Novitz,
and B. E. Redman) and is often shortened further to HDB, which is the
term we'll use in this chapter. HDB was conceived to eliminate some of
Version 2 UUCP's deficiencies. For example, new transfer protocols
were added, and the spool directory was split so that now there is one
directory for each site with which you have UUCP traffic.
The implementation of UUCP currently distributed with Linux is Taylor
UUCP 1.06, which is the version this
chapter is based upon.[1] Taylor UUCP Version 1.06 was released in August 1995.
Apart from traditional configuration files, Taylor UUCP can also be compiled
to understand the newstyle—a.k.a. Taylor—configuration files.Taylor UUCP is usually compiled for HDB compatibility, the Taylor
configuration scheme, or both. Because the Taylor scheme is much more
flexible and probably easier to understand than the often obscure HDB
configuration files, we will describe the Taylor scheme below.This chapter is not designed to exhaustively describe the command-line
options for the UUCP commands and what they do, but to give you an
introduction to how to set up a working UUCP node. The first section gives
a gentle introduction about how UUCP implements remote execution and file
transfers. If you are not entirely new to UUCP, you might want to skip to
the section the section called UUCP Configuration Files” later in this
chapter, which explains the various files used to set up UUCP.We will, however, assume that you are familiar with the user programs of
the UUCP suite, uucp and uux.
For a description, refer to the online manual pages.
Besides the publicly accessible programs uucp and
uux, the UUCP suite contains a number of commands used
for administrative purposes only. They are used to monitor UUCP traffic
across your node, remove old log files, or compile statistics. None of these
will be described here because they are peripheral to the main tasks of UUCP.
Besides, they're well documented and fairly easy to understand; refer to
the manual pages for more information. However, there
is a third category, which comprise the actual UUCP
“work horses.” They are called uucico
(where cico stands for copy-in copy-out), and
uuxqt, which executes jobs sent from remote systems.
We concentrate on these two important programs in this chapter.If you're not satisfied with our coverage of these topics, you should read
the documentation that comes with the UUCP package. This is a set of
Texinfo files that describe the setup using the Taylor configuration
scheme. You can convert the Texinfo files into a dvi file
using the texi2dvi (found in the Texinfo package in your
distribution) and view the dvi file using the
xdvi command.
Guylhem Aznar's UUCP-HOWTO is another good source for information about UUCP
in a Linux environment. It is available at any Linux Documentation
Project mirror and is posted regularly to
comp.os.linux.answers.
There's also a newsgroup for the discussion of UUCP called comp.mail.uucp. If you have questions
specific to Taylor UUCP, you may be better off asking them there,
rather than on the comp.os.linux.* groups.UUCP Transfers and Remote Execution
The concept of jobs is vital to understanding UUCP.
Every transfer that a user initiates with uucp or
uux is called a job. It is made up of
a command to be executed on a remote system, a collection of files to
be transferred between sites, or both.As an example, the following command makes UUCP copy the file
netguide.ps to a remote host named
pablo and execute the
lpr command on
pablo
to print the file:$ uux -r pablo!lpr !netguide.ps
UUCP does not generally call the remote system immediately to execute a job
(or else you could make do with kermit). Instead, it
temporarily stores the job description away. This is called
spooling. The directory tree under which jobs are stored
is therefore called the spool directory and is generally
located in /var/spool/uucp. In our example, the job
description would contain information about the remote command to be executed
(lpr), the user who requested the execution, and a couple
of other items. In addition to the job description, UUCP has to store the
input file netguide.ps.The exact location and naming of spool files may vary, depending on
some compile-time options. HDB-compatible UUCPs generally store spool
files in a /var/spool/uucp subdirectory with the name
of the remote site. When compiled for Taylor configuration, UUCP creates
subdirectories below the site-specific spool directory for different types
of spool files.At regular intervals, UUCP dials up the remote system. When a connection to
the remote machine is established, UUCP transfers the files describing the
job, plus any input files. The incoming jobs will not be executed
immediately, but only after the connection terminates. Execution is handled
by uuxqt, which also takes care of forwarding any jobs that
are designated for another site.
To distinguish between more and less important jobs, UUCP associates a
grade with each job. This is a single digit ranging
from 0 through 9, A through Z, and a through z, in decreasing precedence. Mail
is customarily spooled with grade B or C, while news is spooled with grade
N. Jobs with higher grades are transferred earlier. Grades may be assigned
using the –g flag when invoking uucp
or uux.You can also prohibit the transfer of jobs below a given grade at certain
times. To do this we set the maximum spool grade
that will be prohibited during a conversation. The maximum spool grade
defaults to z, meaning all grades will be transferred every time. Note the
semantic ambiguity here: a file is transferred only if it has a grade
equal to or above the maximum spool grade threshold.The Inner Workings of uucico
To understand why uucico needs to know particular
information, a quick description of how it actually connects to a remote
system is helpful.
When you execute uucico -s system
from the command line, uucico first has to connect
physically. The actions taken depend on the type of connection to
open. Thus, when using a telephone line, it has to find a modem and dial
out. Over TCP, it has to call gethostbyname to convert
the name to a network address, find out which port to open, and bind the
address to the corresponding socket.
A successful connection is followed by authorization. This procedure
generally consists of the remote system
asking for a login name and possibly a password. This exchange is commonly
called the login chat. The authorization procedure is
performed either by the usual
getty/login suite,
or on TCP sockets by uucico itself. If authorization
succeeds, the remote end fires up uucico. The local copy of
uucico that initiated the connection is referred to as
master, and the remote copy as slave.
Next follows the handshake phase : the master sends
its hostname plus several flags. The slave checks this hostname for
permission to log in, send, and receive files, etc. The flags describe
(among other things) the maximum grade of spool files to transfer. If
enabled, a conversation count or call sequence number
check takes place here. With this feature, both sites maintain a count of
successful connections, which are compared. If they do not match, the
handshake fails. This is useful to protect yourself against impostors.Finally, the two uucicos try to agree on a common
transfer protocol. This protocol governs the way data is
transferred, checked for consistency, and retransmitted in case of an error.
There is a need for different protocols because of the differing types of
connections supported. For example, telephone lines require a
“safe” protocol, which is pessimistic about errors, while TCP
transmission is inherently reliable and can use a more efficient protocol that
foregoes most extra error checking.After the handshake is complete, the actual transmission phase begins.
Both ends turn on the selected protocol driver. At this point, the drivers
possibly perform a protocol-specific initialization sequence.The master then sends all files queued for the remote system whose
spool grade is high enough. When it has finished, it informs the slave
that it is done and that the slave may now hang up. The slave now can
either agree to hang up or take over the conversation. This is a
change of roles: now the remote system becomes master, and the local one
becomes slave. The new master now sends its files. When done, both
uucico s exchange termination messages and close the
connection.If you need additional information on UUCP, please refer to the
source code. There is also a really antique article floating around the Net,
written by David A. Novitz, which gives a detailed description of the UUCP
protocol.[2] The Taylor UUCP FAQ also
discusses some details UUCP's implementation. It is posted to
comp.mail.uucp regularly.
uucico Command-line Options
In this section, we describe the most important command-line options for
uucico :– – system, –s systemCalls the named system unless prohibited by call-time
restrictions.–S systemCalls the named system unconditionally.– –master, –r1Starts uucico in master mode. This is the default when
–s or –S is given. All by itself,
the –r1 option causes uucico to try
to call all systems in the sys file described in the
next section of this chapter, unless prohibited by call or retry time
restrictions.– –slave, –r0Starts uucico in slave mode. This is the default
when no –s or –S is
given. In slave mode, either standard input/output are assumed to be
connected to a serial port, or the TCP port specified by the
–p option is used.– –ifwork, –CThis option supplements –s or
–S and tells uucico to call the
named system only if there are jobs spooled for it.– –debug type, –x type, –X typeTurns on debugging of the specified type. Several types can be given as a
comma-separated list. The following types are valid:
abnormal,
chat,
handshake,
uucp-proto,
proto,
port,
config,
spooldir,
execute,
incoming, and
outgoing.
Using all turns on all options. For
compatibility with other UUCP implementations, a number may be specified
instead, which turns on debugging for the first n
items from the above list.Debugging messages will be logged to the Debug
file below /var/spool/uucp.Notes[1]Written and copyrighted by Ian Taylor, 1995.[2]It's also included in the 4.4BSD System Manager's Manual.PrevHomeNextNetWare Server Emulation UUCP Configuration Files
Wyszukiwarka
Podobne podstrony:
x 087 2 uucp config filesx 087 2 uucp misc faqx 087 2 uucp dialinx 087 2 uucp protocolsx 087 2 uucp permissionsx 087 2 intro uucpx 087 2 accounting zeroing counterx 087 2 cnews miscx 087 2 cnews nfsx 087 2 mail deliveryx 087 2 masq namelookupsx 087 2 firewall filteringmethodsx 087 2 accountingx 087 2 firewall filteringUUCP HOWTO pl 1 (2)x 087 2 nis shadow087 092 zzhjfir6ptmapevkxbqtgyde3cqjmuka5gvkruawięcej podobnych podstron