INN provides the news administrator the ability to control which
newsgroups are forwarded on to other news servers and how they will be
forwarded. The most common method uses the NNTP protocol described
earlier, but INN also allows newsfeeds via other protocols, such as UUCP.
The newsfeeds file determines where news articles
will be sent. It normally resides in the /etc/news/
directory.
The format of the newsfeeds is a little complicated at
first. We'll describe the general layout here, and the
newsfeeds(5) manual page describes
what we leave out. The format is as follows:
# newsfeeds file format
site:pattern:flags:param
site2:pattern2\
:flags2:param2 |
Each news feed to a site is described by a single line, or may be
spread across multiple lines using the \ continuation character. The
: characters delimit the fields in each line. The # character at the
start of a line marks that line as a comment.
The site field names the site to which this feed
description relates. The sitename can be coded any way you like and
doesn't have to be the domain name of the site. The site name will be
used later and will refer to an entry in a table that supplies the
hostname to the innxmit program that transmits the
news articles by NNTP to the remote server. You may have multiple
entries for each site; each entry will be treated individually.
The pattern field specifies which news groups are
to be sent to this site. The default is to send all groups, so if that
is what you want, just make this field empty. This field is usually a
comma-delimited list of pattern-matching expressions. The * character
matches zero or more of any character, the . character has no special
significance, the ! character (if used at the start of an expression)
performs a logical NOT, and the @ character at the start of a
newsgroup name means “Do not forward any articles that are
posted or crossposted to this group.” The list is read and
parsed from left to right, so you should ensure that you place the
more specific rules first. The pattern:
rec.crafts.brewing*,!rec.crafts.brewing.poison,@rec.crafts.brewing.private |
would send all of the rec.crafts.brewing news heirarchy
except the rec.crafts.brewing.poison.
It would not feed any articles that were either posted or crossposted to the
rec.crafts.brewing.private newsgroup; these articles will
be trapped and available only to those people who use this server.
If you reversed the first two patterns, the first pattern would be overridden
by the second and you would end up feeding articles for the
rec.crafts.brewing.poison newsgroup. The same is true of
the first and last patterns; you must always place the more specific
patterns before any less specific patterns for them to take effect.
flags controls and places constraints on the feed
of news articles to this site. The flags field is a
comma delimited list can contain any of the items from the following list, delimited by commands:
- <size
Article must be less then size bytes.
- Aitems
Article checks. items can be one or more of
d (must have Distribution header) or
p (don't check for site in Path header).
- Bhigh/low
Internal buffer size before writing to output.
- H[count]
Article must have less then count hops; the default is 1.
- Isize
Internal buffer size (for a file feed).
- Mpattern
Only moderated groups that match the pattern.
- Npattern
Only unmoderated groups that match the pattern.
- Ssize
Start spooling if more than size bytes get queued.
- Ttype
Feed types: f (file), m (funnel; the
param field names the entry that articles will be
funneled to), p (pipe to program), c
(send to stdin channel of the param field's
subprocess), and x (like c, but handles commands on stdin).
- Witems
What to write: b (article bytesize), f
(full path), g (first newsgroup), m
(Message ID), n (relative path), s (site
that fed article), t (time received), *
(names of funnel feed-ins or all sites that get the article),
N (newsgroups header), D (distribution
header), H (all headers), O (overview
data), and R (replication data).
The param field has special coding that is dependent on
the type of feed. In the most common configuration it is where you specify
the name of the output file to which you will write the outgoing feed.
In other configurations you can leave it out. In yet other configurations
it takes on different meanings. If you want to do something unusual, the
newsfeeds(5) manual page will explain the use of the
param field in some detail.
There is a special site name that should be coded as ME
and should be the first entry in the file. This entry is used to control
the default settings for your news feeds. If the ME
entry has a distribution list associated with it, this list will
be prepended to each of the other site entries before they are sent.
This allows you to, for example, declare some
newsgroups to be automatically fed, or automatically blocked from
feeding, without having to repeat the pattern in each site entry.
We mentioned earlier that it was possible to use some special feeds to
generate thread data that makes the newsreader's job easier. We'll do this
by exploiting the overchan command that is part of the
INN distribution. To do this, we've created a special local feed called
overview that will pass the news articles to the
overchan command for processing into overview data.
Our news server will provide only one external news feed, which goes to
the Groucho Marx University, and they receive articles for
all newsgroups except the control and
junk newsgroups, the
rec.crafts.brewing.private newsgroup, which will be
kept locally, and the rec.crafts.brewing.poison
newsgroup, which we don't want people from our brewery seen posting to.
We'll use the nntpsend command to transport the news via
NNTP to the news.groucho.edu server. nntpsend requires us to use the “file”
delivery method and to write the article's pathname and article ID. Note
that we've set the param field to the name of the output
file. We'll talk a little more about the nntpsend
command in a moment. Our resulting newsfeed's configuration is:
# /etc/news/newsfeeds file for the Virtual Brewery
#
# Send all newsgroups except the control and junk ones by default
ME:!control,!junk::
#
# Generate overview data for any newsreaders to use.
overview::Tc,WO:/usr/lib/news/bin/overchan
#
# Feed the Groucho Marx University everything except our private newsgroup
# and any articles posted to the rec.crafts.brewing.poison newsgroup.
gmarxu:!rec.crafts.brewing.poison,@rec.crafts.brewing.private:\
Tf,Wnm:news.groucho.edu
# |
The nntpsend program manages the transmission of
news articles using the NNTP protocol by calling the
innxmit command. We saw a simple use of the
nntpsend command earlier, but it too has a
configuration file that provides us with some flexibility in how we
configure our news feeds.
The nntpsend command expects to find batch files
for the sites it will feed. It expects those batch files to be named
/var/spool/news/out.going/sitename. innd
creates these batch files when acting on an entry in the
newsfeeds, which we saw in the previous
sections. We specified the sitename as the filename in the
param field, and that satisfies the
nntpsend command's input requirements.
The nntpsend command has a configuration file called
nntpsend.ctl that is usually stored in the
/etc/news/ directory.
The nntpsend.ctl file allows us to associate a fully
qualified domain name, some news feed size constraints, and a number of
transmission parameters with a news feed site name. The sitename is a means
of uniquely identifying a logical feed of articles.
The general format of the file is:
sitename:fqdn:max_size:[args] |
The following list describes the elements of this format:
- sitename
The sitename as supplied in the newsfeeds file
- fqdn
The fully qualified domain name of the news server to which we will be feeding
the news articles
- max_size
The maximum volume of news to feed in any single transfer
- args
Additional arguments to pass to the innxmit command
Our sample configuration requires a very simple
nntpsend.ctl file. We have only one news feed. We'll
restrict the feed to a maximum of 2 MB of traffic and we'll pass an
argument to the innxmit that sets a 3-minute
(180 second) timeout. If we were a larger site and had many news feeds,
we'd simply create new entries for each new feed site that looked much
the same as this one:
# /etc/news/nntpsend.ctl
#
gmarxu:news.groucho.edu:2m:-t 180
# |
