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1989-06-27
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IIIInnnnssssttttaaaalllllllliiiinnnnggg
g ````````CCCC NNNNeeeewwwwssss'''''''' NNNNeee
ttttwwwwoooorrrrkkkk NNNNeeeewwwwssss SSSSoooof
fffttttwwwwaaaarrrreeee
Geoff Collyer
Department of Statistics
University of Toronto
This document describes the flow of network news
within and between machines, what each component of C
news does, and how to install C news.
IIIInnnnttttrrrroooodddduuuuccccttttiiiioooon
nn
Network news (or _n_e_t_n_e_w_s for short) consists of a collection
of messages formatted similarly to ARPAnet mail (see ARPA Inter-
net RFC 1036 for details), widely spread. The logical network,
imposed on top of various real networks, formed by the set of all
interconnected sites exchanging network news is called ``Usenet''
and was formed in 1979, radiating out from Duke University. Net-
news is propagated between cooperating machines by a flooding
algorithm, with some loop prevention heuristics: each machine
sends its neighbours news that the neighbours have (probably) not
yet seen.
Flow of netnews between machines may be achieved by use of
any network which can transmit an arbitrary stream of (at least
7-bit) ASCII code, unmodified. If a network cannot transmit
ASCII intact (e.g. BITNET), it is possible to encode netnews
before transmission across the network and decode it upon recep-
tion from the network. Since one cannot be certain that one's
network neighbours will be up and reachable at all times, outgo-
ing netnews must be queued, at least in the case of network trou-
ble. To date, at least these networks, protocols and media have
been used to transmit netnews correctly: UUCP, RS232, NNTP, Eth-
ernet(Reg), the ARPA Internet, Datakit(Reg), ACSnet, magnetic
tape, SMTP, and BITNET, though at least the last two require some
form of encapsulation to avoid corruption of articles; SMTP
because some common implementations get the newline-CRLF mappings
wrong, thus throwing off byte counts in batches, and BITNET
because of its Procrustean chopping, expanding, mapping, bashing
and smashing of all data sent through it (sending lines of 80 or
fewer characters of letters of either case and digits and plus
and minus appears to be safe).
- 2 -
Netnews arrives via some network, which causes a command to
be executed upon arrival (e.g. _r_n_e_w_s). _r_n_e_w_s typically
pools
the inbound netnews for later processing. Eventually (often
within the hour or at the end of the business day), the input
queue is run and the netnews is stored locally, typically under
/_u_s_r/_s_p_o_o_l/_n_e_w_s, and queued for transmission to netn
ws neigh-
bours. Once stored on disk, netnews may be read by any of a col-
lection of unprivileged news readers, including _c_a_t(1). _E_x_p_i_
_e
is run typically each night to remove old netnews from disk.
C News was originally written to provide a much faster and
smaller, more robust, reliable and correct implementation of net-
news software than B 2.11 news. We believe that C News is also
faster, smaller and more robust than B 3.0 news. B 3.0 news has
many more features; take that as you will.
CCCC NNNNeeeewwwwssss CCCCoooommmmppppoooonnnn
eeennnnttttssss....
_R_n_e_w_s invokes the input subsystem, which spools incoming
netnews in its original form, as received, typically in
compressed batches. Periodically, the input queue should be run
by invoking _n_e_w_s_r_u_n, thus uncompressing any compressed input and
feeding it to _r_e_l_a_y_n_e_w_s.
_R_e_l_a_y_n_e_w_s files incoming netnews as articles on disk
and
initiates spooled transmission to other machines, often by simply
writing the names of the disk files containing the articles on
the ends of `batch' files of file names. Quite a bit of policy
from RFC 1036 is embedded in _r_e_l_a_y_n_e_w_s. _i_n_e_w_s
s a complex
front-end for _r_e_l_a_y_n_e_w_s which implements much of the per-
ite
policy on news posting. _i_n_e_w_s is a fairly-slow shell script
which is adequately fast for most sites, but it will need to be
replaced by something more streamlined for sites which gateway
mailing lists into netnews, for example.
The output _b_a_t_c_h_e_r reads lists of file names and generates
news batches (see RFC 1036 or _n_e_w_s(5) for the format) of
prescribed sizes and queues the batches for transmission to other
sites. The batcher is run asynchronously with _r_e_l_a_y_n_e_w_s, t
pi-
cally once an hour outside of business hours.
_E_x_p_i_r_e is generally run once per night to remove from disk
news articles older than a few days. _E_x_p_i_r_e can use different
expiry criterion for different newsgroups and can archive arti-
cles instead of removing them. _E_x_p_i_r_e also runs asynchronously
with _r_e_l_a_y_n_e_w_s.
There are many news readers. C News comes with a limited
news reader (_r_e_a_d_n_e_w_s by Michael Rourke) sufficient to repla
e
long-winded /_e_t_c/_m_o_t_ds but you will want a heavy-duty news reader
if you plan to read more than local news groups. We recommend _r_n
by Larry Wall, available from your netnews neighbours or your
nearby ccccoooommmmpppp....ssssoooouuuurrrrcccce
eessss....uuuunnnniiiixxxx archive site. There are others:
_v_n and
_v_n_e_w_s are two.
- 3 -
PPPPrrrreeeeppppaaaarrrraaaattttiiiioooonnnn f
fffoooorrrr IIIInnnnssssttttaaaallllllllaaaatt
tiiiioooonnnn
Netnews consumes a lot of disk space and often a lot of
transmission time. Here are some relevant measurements regarding
a full netnews feed as of the time of writing (January 1989),
taken from _n_e_w_s._l_i_s_t_s: a day's netnews is about 3Mb and 1
400
articles in 450 newsgroups. Years ago, sites often kept 14 days
of netnews on disk, but now many sites keep news for 3 to 5 days,
thus allowing for the occasional long weekend. Thus a full news
feed expired after 4 days will consume about 12Mb. Some people
feel that news volume is doubling roughly every 16 months. If
this is true, we can expect volume to increase by a factor of 10
in about 4 years to 30Mb per day or 115Mb for 4 days. It is thus
wise planning to set aside a lot of disk space for netnews.
There are two ways to cope with ever-increasing volumes of net-
news: refuse to accept more newsgroups, or expire news after
shorter intervals on disk. A current full feed takes just over 7
hours to transmit at 1200 baud, so for dial-up connections one
clearly wants the fastest modems one can afford.
Clearly, transmitting a full news feed is a non-trivial com-
mitment of resources, so you may have some difficulty in finding
a site willing to supply one. Such a site may in turn expect you
to feed yet other sites. You will need to agree with your pros-
pective netnews neighbour(s) upon transfer media, protocols and
networks.
Before proceeding to install C News, you should read this
document through to the end, probably read the companion document
_T_h_e _I_n_t_e_r_f_a_c_e _B_e_t_w_e_e_n _C _N_e_w_s _
_n_d _T_h_e _O_u_t_s_i_d_e _W_o_r_l_d, and possibly
read selected items in the _C _N_e_w_s _I_m_p_l_e_m_e_n_t_o_r'
s _N_o_t_e_b_o_o_k and the
manual pages.
You will need to assign a user id and group id to netnews
(often new ids called ``news''); initialise these directories:
NEWSCTL (typically ////uuuussssrrrr////lllliiiibbbb//
//nnnneeeewwwwssss), NEWSBIN (////uuuussssrrrr////
llliiiibbbb////nnnneeeewwwwssssbbbbiiiinnnn),
and NEWSARTS (////uuuussssrrrr////ssssppppoooooooo
lll////nnnneeeewwwwssss); and install each subsystem.
NEWSCTL and NEWSARTS are logically one subtree, defining a news
data base, but are split for backward compatibility with older
news software, particularly old news readers. NEWSBIN contains
programs and shell scripts which might be common amongst machines
sharing a common architecture (e.g. Sun 3's); NEWSCTL////bbbbiiiin
nn may
override these. The goal is to install the subsystems, integrate
them into a working news system, and configure the news system to
communicate with other news systems.
There are a few key files that must exist before any serious
attempt may be made to operate the news software. NEWSCTL////aaaacccc
tttiiiivvvveeee
is the list of newsgroups that this site knows (is willing to
accept or individually reject), and must be owned by the NEWS
userid (the userid that owns NEWSBIN////rrrreeeellllaaaayyyy
///rrrreeeellllaaaayyyynnnneeeewwwwssss, typicall
_n_e_w_s). You will probably want to get your initial aaaacccctt
ttiiiivvvveeee file
from your upstream feed and edit it to suit the set of groups you
wish to receive. Be sure to make the second field more than five
- 4 -
digits wide, by adding leading zeroes (ten digits is a conserva-
tive width). NEWSCTL////ssssyyyyssss defines the newsgroups that
this site
is willing to accept and describes how they are to be forwarded
to its neighbours. NEWSCTL////sssseeeerrrrvvvveeeerrrr c
ntains the hostname of your
file server, if you have multiple machines sharing news via a
network file system. NEWSCTL////wwwwhhhhooooaaaammmmiiii
similarly contains the name
by which a cluster of machines sharing news is to be known for
purposes of news. NEWSCTL////mmmmaaaaiiiillllnnnnaaaamm
mmeeee is optional and contains the
full (possibly dotted) name by which your cluster is known for
purposes of mail. NEWSCTL////oooorrrrggggaaaannnniiiiss
ssaaaattttiiiioooonnnn (or NEWSCTL////oooorrrrgggga
aannnniiiizzzzaaaattttiiiioooonnnn
if you insist) contains the name of your organisation, which will
be copied into the OOOOrrrrggggaaaannnniiiizzzzaaaa
tttiiiioooonnnn:::: header of articles posted
locally, by default. NEWSCTL////mmmmaaaaiiiillllppppaaaat
ttthhhhssss defines mail routes to
machines which contain aliases for postings to moderated news-
groups. NEWSCTL////lllloooogggg, NEWSCTL////eeeerrr
rrrrrlllloooogggg, NEWSCTL////hhhhiiiissssttttoo
oorrrryyyy,
NEWSCTL////hhhhiiiissssttttoooorrrryyyy....ddddi
iirrrr, and NEWSCTL////hhhhiiiissssttttoooorrrryyy
y....ppppaaaagggg must exist and be
owned by the NEWS userid. Tentative versions of all these files
are built by the installation procedures, but it is quite likely
that you'll have to edit some of them.
CCCC NNNNeeeewwwwssss IIIInnnnssssttttaaaallll
lllaaaattttiiiioooonnnn
Proceed to the ccccoooonnnnffff directory of the distribution.
There is
a major shell file here, named bbbbuuuuiiiilllldddd, that will
interrogate you
at length and construct shell files to do the real work. You may
need to do ``chmod +x build'' before running it, to make it exe-
cutable.
You will probably need your system's manuals on hand to
answer bbbbuuuuiiiilllldddd's questions. Another terminal (or
another window,
on a bitmap display) would also be useful. You'd best be
prepared to take notes, also, as bbbbuuuuiiiilllldddd will occa
ionally suggest
that something be checked when you're done.
BBBBuuuuiiiilllldddd itself does not alter any files or per
orm any instal-
lation chores: all it does is create shell files in the ccccoooonn
nffff
directory. If you already know something about news software, or
are merely suspicious that bbbbuuuuiiiilllldddd hasn't done e
erything right,
you should probably read the shell files before running them.
There are four of them: ddddooooiiiitttt....rrrroooo
oootttt, ddddooooiiiitttt....bbbbiiiinnnn, dddd
oooiiiitttt....nnnneeeewwwwssss, and
aaaaggggaaaaiiiinnnn....rrrrooooooootttt.
DDDDooooiiiitttt....rrrrooooooootttt sets up th
major directories for news, and sets
their ownerships correctly. It typically will have to be run as
_r_o_o_t to have adequate permissions for all of this. It is brief.
DDDDooooiiiitttt....bbbbiiiinnnn does most of the
ork of building and installing
the programs. It should be run as the user who owns the distri-
bution directories and will own the executable programs under
NEWSBIN.
DDDDooooiiiitttt....nnnneeeewwwwssss does some
ther small chores and installs control
files. If any of the control files already exist, it will com-
plain and refuse to overwrite them, as a safety precaution. It
- 5 -
should be run as the owner of the news files. Since many of the
files it is installing are built by ddddooooiiiitttt....bbbbi
iiinnnn, that should be run
first.
Finally, aaaaggggaaaaiiiinnnn....rrrroooooooot
ttt tends to ownership and permission
changes on a few programs that need to run set-userid. It
requires the ability to change ownerships and to set permissions
on the files afterwards, which usually means running it as _r_o_o_t.
It too is brief.
There are undoubtedly strange systems out there that bbbbuuuuiii
illlldddd
and friends are not smart enough to cope with. In such cases it
will be necessary to edit the shell files before running them, or
to use them as guides and do the work by hand. In particular,
systems that require strange options in MMMMaaaakkkkeeeeffffii
illlleeees will need to
have those inserted by hand.
If you want to test pieces of C News without installing
them, some (not all) of the subsystems have a ``make r'' feature
that runs a regression test. Note: almost all of these require
that NEWSCTL////bbbbiiiinnnn////ccccoooonnnnffffii
iigggg, or its local equivalent, be in place
already so that shell files can find out what PATH (etc.) they
should be using.
Note that it is easy to build a test news system which is
completely independent of other existing news systems on the same
machine, or to build one which shares its NEWSBIN with another C
news system, or shares input of articles (e.g. running an old B
news system and a new C news system off the same stream of input
until you are confident that your new C news system is operating
to your satisfaction). See _s_u_b_s_t(1) for the mechanism which per-
mits quickly changing all the places that know the location of
NEWSCTL////bbbbiiiinnnn////ccccoooonnnnffffiiiig
gg.... After that, edit this news system's
NEWSCTL////bbbbiiiinnnn////ccccoooonnnnffffiiiig
gg and things should be set up for separate
existence.
FFFFiiiirrrrsssstttt NNNNeeeewwwwssss
When you arrange to get a news feed from your neighbor, you
should also ask him to send you the current set of articles in
the newsgroup nnnneeeewwwwssss....aaaannnnnnnnoooou
uunnnncccceeee....nnnneeeewwwwuuuusssseeeerrr
ssss. Several of these are very
important reading for people who are new to the net.
UUUUnnnnuuuussssuuuuaaaallll SSSSyyyysssstttte
eeemmmmssss
We believe that C News runs fine on 16-bit machines, but it
hasn't been tested very thoroughly on them lately. It will not
perform quite as well with the more limited space.
Machines with very old compilers can be a headache. There
are some hooks in hhhh////nnnneeeewwwwssss....hhhh
for doing without ``void'' and
``unsigned long'', two particular problem areas, but they have to
be arranged manually; bbbbuuuuiiiilllldddd does not know about t
em.
- 6 -
Some very old systems cannot do _s_e_t_u_i_d(_g_e_t_e_u_i_
()), which
makes it impossible for a daemon to make directories and get the
ownership right. We provide a small program, sssseeeettttnnnneee
ewwwwssssiiiiddddssss, to run
setuid-root. RRRReeeellllaaaayyyynnnneeeewwwwssss
knows about it and invokes it if
_s_e_t_u_i_d(_g_e_t_e_u_i_d()) fails; it then sets permissions co
rectly and
re-invokes rrrreeeellllaaaayyyynnnneeeewwwwssss.
he code is short enough to be read and
understood in full, so that the suspicious system administrator
can be sure that this setuid-root program is not going to do
something awful.