NAME¶
leafnode - NNTP server for small (dialup) sites
SYNOPSIS¶
leafnode
DESCRIPTION¶
Leafnode is a USENET package intended for small sites, where there are
few users and little disk space, but where a large number of groups is
desired.
The design of
leafnode is intended to self-repair after problems, and to
require no manual maintenance.
The
leafnode program itself is the NNTP server. It is run from
inetd(8),
xinetd(8) or
tcpserver when someone wants to
read news. The other parts of the package,
fetchnews and
texpire, are responsible for fetching new news from another server, and
for deleting old news.
ACCESS CONTROL¶
No authentication or access control is supported. This is a deliberate omission:
Implementing this is a job which should not be redone for each and every
service.
It is mandatory that you use external access control mechanisms like
tcpd, inetd/xinetd compiled with libwrap support, tcpserver with -x
option and the like and that these are in effect. tcpd and libwrap are
components of Wietse Venema's fine
tcp_wrappers package.
As a very rough last line of defense against abuse, leafnode will drop
connections from outside your LANs by default. You can configure leafnode to
let go of this restriction (look for the allowstrangers option), but don't do
that unless tight access control is in place. Someone will abuse your computer
sooner or later. Promised.
I recommend that either firewalling or tcpd be used for access control.
FILES¶
All these files and directories
must be readable by the user
"news". It is recommended that, unless otherwise stated, that the
user "news" be the only user in the group "news" and these
files belong to "root:news" (user:group) so leafnode cannot modify
your configuration or filter files.
/etc/news/leafnode should not be writable by the user "news",
but it must be executable for at least any of the group that the user
"news" is in.
/etc/news/leafnode/config contains the
configuration parameters for
leafnode. It
must not be writable
by the user "news". Set this to owner root:news and mode 640. For
details, see CONFIGURATION below.
/var/spool/news must also be readable and writable by the user
"news". It contains the news articles; e.g.
/var/spool/news/alt/fan/agulbra contains the articles in the
alt.fan.agulbra group. Each directory contains articles in numbered
files (decimal numbers, monotonically increasing), and a special file called
.overview which contains the "Subject", "From",
"Date", "Message-ID", "References",
"Bytes" and "Lines" headers for each article in the group.
Several subdirectories are special:
/var/spool/news/leaf.node contains the files that leafnode creates during
operation, for example the
groupinfo file which contains information
about each USENET newsgroup. This file is built by
fetchnews (8). You
can force a complete rebuild of the groupinfo file by calling
fetchnews
with the parameter -f (see
fetchnews (8)).
/var/spool/news/out.going contains local postings that
fetchnews(8) is to pass to the upstream NNTP server. After a posting
has been successfully written to disk, its u+r permission flag is set. This
flag is interpreted by
fetchnews(8) as "you may post this
article". This prevents fetchnews from posting articles that are still
being received from newsreaders. (Note: versions 1.9.23 to 1.9.32 inclusively
used u+x instead, which caused some "stuck post" problems with
articles in the spool when a prior leafnode version was updated to one of
these 10 versions. Updating to leafnode 1.9.33 or later fixes the problem.)
/var/spool/news/failed.postings contains local postings that the upstream
server rejected.
fetchnews(8) will create files in this directory, but
none of the
leafnode programs will delete anything in it.
/var/spool/news/message.id contains hard links to each message; this is
used in place of the
dbz database typically used by bigger servers. (A
directory such as this is probably more efficient for the small servers
leafnode is designed for but scales very badly.)
/var/spool/news/interesting.groups contains one file for each group an
NNTP client has asked to read.
leafnode will update the
ctime
(ls -l usually shows the
mtime, try ls -lc) of the
relevant file when a LISTGROUP, XOVER, XHDR, STAT, HEAD, BODY or ARTICLE
command is issued, when a GROUP or LIST ACTIVE command (the latter only with a
single group, not with patterns) is issued for an interesting group (to avoid
unsubscribing low-traffic groups that are still read) and
fetchnews(8)
will retrieve all new articles in all groups whose files have been either
- - touched during the past two days, or
- - touched more than once, and at least once within the past week.
The timeout is configurable through the
config file variables
timeout_short and
timeout_long. See also
fetchnews(8) for
the
-n option.
/etc/inetd.conf or
/etc/xinetd.conf contains the configuration
which starts
leafnode. It is strongly recommended to start
leafnode as user news.
ENVIRONMENT¶
- LN_REJECT_POST_PRE
- If this variable exists, all POST commands are rejected with a 400 code.
Use only for debugging clients.
- LN_REJECT_POST_POST
- If this variable exists, the POST command is rejected with a 400 code
after the article and CRLF.CRLF has been received. Use only for debugging
clients.
CONFIGURATION¶
All configuration is done using the file
/etc/news/leafnode/config, which
may include a filter description file, filterfile for short, as described
below.
For the purposes of this section, whitespace shall be defined as an arbitrary
sequence consisting of one or more SPACE or HTAB characters, ASCII positions
32 and 9, respectively.
The configuration file is strictly line-oriented with LF or CRLF as line
terminator.
Empty lines and lines consisting of only whitespace, possibly followed by a
comment (introduced by a hash mark (#) and extending through the end of the
line), are skipped.
All other lines have exactly three mandatory fields, a plain text parameter, an
assignment character (=) optionally surrounded by whitespace and a value. The
value is either plain text or - new since leafnode v1.11 - a string in double
quotes with trivial backslash escape (see below).
Plain text starts at the first non-whitespace character and extends through the
last non-whitespace character on the line that is not a comment. A trailing
comment on a line is skipped.
Quoted strings are enclosed in double quote characters ("). The backslash
character (\) is skipped, but it copies the immediately following character
verbatim, so that you can specify the backslash itself by doubling it (\\) or
a double quote character as part of the string by preceding it with a
backslash (\"); the hash mark has no special meaning as command
introducer inside quoted strings. Text after the end of the string is silently
ignored (this may change in future versions). Comments after quoted strings
are ignored.
MANDATORY PARAMETERS
These parameters must be specified for leafnode to work.
- server = news02.example.com
- "server" is used by fetchnews (8) to select what NNTP
server(s) to retrieve news from and to post your articles to. You can
specify more than one news server; in that case, the servers will be
queried from the top down. If you want to post articles, at least one of
your servers should allow you to post. In the example above,
news02.example.com is the news server.
This parameter can be given more than once. Each server starts with a
fresh set of default configuration options, no inheritance takes place
from the previous server definition. Only options explicitly marked
"server-specific" can be set on a per server basis,
"general" options are set for all servers at the same time.
- expire = 5
- "expire" is the number of days an article should be kept around.
In the example, five days after the article has last been read, it is
deleted by texpire (8). This value MUST be at least 1. This
parameter is global, see the introductory paragraph of the following
GENERAL OPTION PARAMETERS section to find out what this means.
GENERAL OPTIONAL PARAMETERS
These options can only be configured once in the configuration file, and take
effect for leafnode as a whole. It does not matter where these are specified
relative to server= options, but for clarity, you are encouraged to place
these before the first server= line. Specifying each of the global options
more than once lets the last copy take effect, but may cause errors in the
future.
- hostname = host.domain.country
- By default, leafnode tries hard to figure the host name of your computer,
skipping inadequate (non-unique) names if possible. It will look up your
computer's host name with gethostname(3) and then try to qualify the name
with gethostbyname(3) if necessary. Common sources for the full name
therefore are /etc/hosts, NIS and DNS, but consult your system
documentation for details.
If leafnode fails to determine the host name, this is usually a hint that
your system is not configured properly, or it has a hostname that is
unsuitable for the domain part of a Message-ID, for example,
"localhost.localdomain", and you should fix the name service
configuration. Adding a unique fully-qualified host name to /etc/hosts is
usually sufficient. Please see README-FQDN for more details.
You can configure the unique fully-qualified host name here as well, but
this is not recommended and discouraged.
- create_all_links = 1
- Normally, fetchnews will store articles only in the newsgroups which it
considers interesting. With this option set, fetchnews will create
hardlinks for all newsgroups in the Newsgroups: header that it knows
about. This may be of interest if you want to apply a score- or killfile
to the local Xref: line.
- maxfetch = 1000
- "maxfetch" specifies the maximum number of articles
fetchnews (8) should fetch from the upstream server in each group.
Its use is not advised, because if you use it you will not see all the
traffic in a group. By default there is no limit.
- initialfetch = 1
- "initialfetch" defines how many articles from a newly subscribed
group should be fetched. The default is to fetch all old articles, which
can get quite time-consuming when subscribing to a very busy group. This
is equivalent to setting initialfetch to zero. If you want to get no old
articles when subscribing to a new group, you should set initialfetch to
one, as in the example above.
groupexpire very.crowded.group = 1
- groupexpire very.crowded.hierarchy.* = 1
- "groupexpire" makes it possible to adjust expiry times for
individual groups. Expiry times are given in days. 0 means "use the
default", negative values prevent the expire process for this group
altogether (you can consider this an archive mode). This value is used by
texpire (8). You can specify as many groupexpire lines as you like.
It is possible to specify glob (7)-like wildcard expressions.
- maxage = 10
- If an article turns up on your upstream news server which is older than
"maxage" days it will not been fetched even if you don't have it
yet. This is useful if your upstream server gets occasional
"hiccups". The default is set to 10. If you want to switch this
feature off, set maxage to some very large value, such as 20000 (this is
equivalent to roughly 54 years).
- maxold = 10
- Is synonymous to maxage, see above.
- maxlines = 2000
- If you want to avoid receiving very large articles, you may set the
"maxlines" parameter to the maximal number of lines an article
should have. By default, this feature is switched off.
- minlines = 2
- Sometimes newsgroups are spammed with empty postings. To reject these
postings, you can set the "minlines" parameter. Setting minlines
to a value larger 4 is probably not a good idea since you will also start
to kill "real" postings then. By default, this feature is
switched off.
- maxbytes = 100000
- If you want to avoid receiving very large articles, instead of using the
"maxlines" parameter you can also use the "maxbytes"
parameter. By default, this feature is switched off.
- maxcrosspost = 5
- If you want to combat spam, you can filter out all postings that are
posted to more than a certain number of newsgroups. The number is defined
by setting "maxcrosspost". Setting this parameter to very low
values is probably a bad idea. This feature is switched off by
default.
- maxgroups = 5
- Synonymous for maxcrosspost. See above.
- filterfile = /etc/news/leafnode/filters
- Leafnode can filter the input headers for arbitrary regular expressions.
These are stored in a file designated "filterfile". The format
of "filterfile" is very simple: one perl-compatible regular
expression per line. If one of the regular expressions fits to a header to
be downloaded, the body of that article will be rejected. This feature is
switched off by default. The format of the regular expressions is
described in pcre(3).
- timeout_short = 2
- By default, a group that has been accidentally touched is being fetched
for two days. You can change this time by changing timeout_short.
- timeout_long = 7
- By default, a group that has not been read at all is being fetched for
seven days before being unsubscribed. This interval can be changed by
setting timeout_long to a different value.
- timeout_active = 90
- By default, active files from the upstream servers are re-read every 90
days. This interval can be changed by setting timeout_active to a
different value. Be aware that reading an active file transfers about one
MB of information if the server that you are using carries a reasonable
number of groups (i. e. around 20,000).
- timeout_client = 900 (since v1.9.23)
- By default, leafnode will drop the connection 900 seconds (15 minutes)
after seeing the last command from the client. You can change the timeout
here. Setting it too low (like below 5 minutes) will annoy your users and
consume more system resources for re-reading all the files.
- timeout_fetchnews = 300 (since v1.9.52)
- Fetchnews will, since v1.9.52, assume the upstream server has become
wedged after waiting for a reply for 300 seconds. You can change the
timeout here.
- timeout_lock = 5 (since v1.9.54)
- Configure how many seconds the leafnode programs (applyfilter,
checkgroups, fetchnews, texpire) will wait for the lock file before
aborting. Setting this to 0 means to wait indefinitely. NOTE: you
can override this by setting the environment variable LN_LOCK_TIMEOUT
(note it is not LN_TIMEOUT_LOCK). The default is 5 seconds.
- delaybody = 1
- With this option set, fetchnews (8) fetches only the headers of an
article for visual inspection. Only when the headers have been read, the
bodies of the articles will be retrieved the next time fetchnews
(8) is called. This can save a huge amount of download time and disk
space.
- delaybody_in_situ = 1 (since v1.9.41)
- This is only applicable with delaybody=1.
By default, leafnode will give the full downloaded article a new article
number so they appear as new in your newsreader. This does not work for
all newsreaders. With this option set, leafnode will retain the original
article number. You'll have to figure out how to tell your newsreader to
show old articles. This option defaults to 0. It is highly
recommended to leave it unset.
- debugmode = 1
- With this option set, fetchnews (8), texpire (8) and
leafnode (8) will start to log lots of debugging output via
syslog (8) at facility news and priority debug. Use it for tracking
down problems with your feed. debugmode should be left at 0 for regular
use because it can log enormous amounts of data. The higher the number,
the more will be logged. Choosing a figure greater than 3 will not make a
difference at the moment.
- allow_8bit_headers = 1 (since v1.9.25)
- By default, leafnode rejects local posts that have 8-bit characters in
their headers, because they violate relevant standards, particularly
RFC-2822 (which RFC-1036 is based on) that demands that Usenet news
headers (as mail headers) must be pure 7-bit US-ASCII, with only
whitespace allowed from the control characters.
However, as UTF-8 is to come, and some national hierarchies, particularly
the Norwegian and Danish (no.*, dk.*) seem to have agreed on preferring
just-send-eight over RFC-2047, you can set this option to allow 8-bit data
in headers. Leafnode will however add a warning header if 8-bit data is
present, stating that the site administrator allowed this.
There is no way to make leafnode accept non-whitespace control characters in
headers.
- allowSTRANGERS = MAGIC (since v1.9.23)
- By default, leafnode refuses connections from outside your LANs. Check
config.example for how to use this parameter to let strangers connect to
your leafnode. Instead of MAGIC, you have to write a number as mentioned
in config.example. Note that capitalization matters.
- linebuffer = 1
- By default, stdout and sometimes stderr of applications are set to
"fully buffered" unless connected to terminals. Use this option
to explicitly request line buffered mode for stdout and stderr.
- clamp_maxage = 0
- By default, leafnode will derive a "maxage" argument from the
expire time that is applicable to the group (groupexpire if set, expire
otherwise), to prevent fetching articles again that were once there and
then cleared by texpire(8). Set clamp_maxage=0 to get rid of this
behaviour.
- article_despite_filter = 1 (since v1.9.33)
- By default, fetchnews will request HEAD and BODY separately if a filter
file is defined and delaybody is off. For high latency, high throughput
links (such as interleaved DSL or satellite links), it may be faster to
request head and body together with an ARTICLE command and ignore the body
if the filters apply (though it may not be cheaper if you pay per MByte),
enabling this option will force leafnode to use the ARTICLE command in
spite of filters being defined. (Note that in delaybody mode, HEAD and
BODY will ALWAYS be requested separately.)
- newsadmin = news@leafnode.example.org (since v1.9.47)
- This option sets the From: address for the placeholder article, it should
be the news administrator's mail address. It defaults to news@HOSTNAME,
where HOSTNAME is leafnode's hostname.
SERVER-SPECIFIC OPTIONAL PARAMETERS
These options can only be placed after the server= line of the server to which
you would like these to apply, and they always pertain to the preceding
server= line. Specifying them before the first server= line is an error.
- username = myname
- If any of your news servers requires authentication, you can enter your
username on that server here. This field may occur multiple times, once
after each server definition. See the introduction of this CONFIGURATION
section for information on how to quote myname.
- password = mypassword
- If any of your news servers requires authentication, you can enter your
password on that server here. This field may occur multiple times, once
after each server definition. Since the password is available in clear
text, it is recommended that you set the rights on the config file as
restrictive as possible, otherwise other users of your computer will be
able to get your password(s) from that file. See the introduction of this
CONFIGURATION section for information on how to quote
mypassword.
- port = 8000
- By default, fetchnews tries to connect to its upstream news servers on the
NNTP port (119). If your servers run on a different port, you can specify
those here. This field may occur multiple times, once after each server
definition.
-
- Note: to modify the port your own leafnode servers listens on,
change the inetd.conf, xinetd.conf configuration file or the
tcpsvd/tcpserver command line. leafnode does not set up its listen port
itself.
- timeout = 30
- By default, leafnode tries to connect for 10 seconds to a server and then
gives up. If you have a slow server, you can try for a longer time by
setting the timeout higher (in this example, 30 seconds). The timeout can
be tuned individually for each server.
- noactive = ANYTHING (v1.9.25 ... v1.11.4)
- noactive = 1 (since v1.11.5)
- If this parameter is set, the active file is never downloaded from this
server. Use this for very slow servers unless they carry groups that other
servers don't offer. Leafnode versions 1.9.25 to 1.11.4 would always
assume that "ANYTHING" had been 1. "noactive = 0" is
supported since v1.11.5.
- nodesc = ANYTHING (until v1.11.4)
- nodesc = 1 (since v1.11.5)
- Some servers do not deliver news groups descriptions correctly because
they cannot parse the XGTITLE and LIST NEWSGROUPS commands. In that case,
put this line after the "server" line. Leafnode versions up to
v1.11.4 would always assume that "ANYTHING" had been 1.
"nodesc = 0" is supported since v1.11.5.
- nopost = 1 (since v1.9.23)
- Prevent posting to this server. You can use this if the upstream won't let
you post but still greet leafnode with 200 or if the upstream doesn't
forward your postings reliably.
- noread = 1 (since v1.9.33)
- Prevent fetching news articles or active files from this server. You can
use this if the upstream is good to post, but too slow to fetch news
from.
- noxover = 1 (since v1.9.47)
- Prevent the use of XOVER on the current server. Fetchnews will use XHDR
instead.
- only_groups_match_all = 1 (since v1.9.52)
- Usually, when cross-posting an article, fetchnews will post the article if
ANY group listed in the Newsgroups: header is matched by the PCRE. With
this option on, ALL groups listed in the Newsgroups: header must match.
This can be used to avoid "poison" groups when you have multiple
upstream servers.
- only_groups_pcre = PCRE (since v1.9.28)
- This parameter lists the Perl-compatible regular expression of groups that
are fetched or posted to this server. The PCRE is automatically anchored
at the left hand side, so you can omit the leading ^. Remember to escape
dots, as in:
de\.comp\.|de\.comm\.
- If this parameter is omitted, all groups are fetched from and posted to
this server.
- Note: you must run fetchnews with the -f option after changing, adding or
removing any only_groups_pcre option.
- Hint: you can use something like this to check your only_groups_pcre
settings:
cut -f1 -d" " @spooldir@/leaf.node/groupinfo \
| pcregrep 'PATTERN'
- post_anygroup = 1 (since v1.9.37)
- This parameter makes leafnode post on this server without checking if it
carries the group an article is posted to. The default is post_anygroup =
0, which means that leafnode will check with a "GROUP" command
if the server carries the group the articles is posted into. Use this on
post-only servers that don't allow the "GROUP" command. Note:
inconsiderate use of this parameter may cause articles to end up in the
failed.postings directory.
OBSOLETE PARAMETERS
- supplement
- is synonymous to server. Don't use it on new installations.
- fqdn
- is synonymous to hostname. Don't use it on new installations.
PROTOCOL¶
Here are the NNTP commands supported by this server:
ARTICLE, BODY, DATE, GROUP, HDR, HEAD, HELP, LAST, LIST, LIST ACTIVE, LIST
ACTIVE.TIMES, LIST EXTENSIONS, LIST NEWSGROUPS, LIST OVERVIEW.FMT, LISTGROUP,
MODE, NEWGROUPS, NEXT, POST, OVER, SLAVE, STAT, XHDR, XOVER. These commands
follow RFC-977 and RFC-2980, except HDR and OVER which are recognized in
anticipation of current NNTP drafts.
Note that the syntax of HDR and OVER may change.
BUGS¶
Leafnode is totally unaware of UTF-8 and will reject a client that posts UTF-8
characters in the header. Current Usefor drafts claim all article headers
UTF-8 encoded Unicode. Leafnode still expects RFC-2047 instead which may
eventually be phased out in favour of UTF-8.
Leafnode stops reading a line at the first NUL character.
Leafnode may not cope well with crosspostings that cross hierarchies if you have
multiple upstream feeds and use the only_groups_pcre configuration option.
Leafnode will only bother to determine the time zone offset for generated Date:
headers for posts that lack them on systems that offer the tm_gmtoff member in
struct tm (commonly BSD and GNU systems).
AUTHOR¶
Written by Arnt Gulbrandsen <agulbra@troll.no> and copyright 1995 Troll
Tech AS, Postboks 6133 Etterstad, 0602 Oslo, Norway, fax +47 22646949.
Modified by Cornelius Krasel <krasel@wpxx02.toxi.uni-wuerzburg.de>,
Randolf Skerka <Randolf.Skerka@gmx.de> and Markus Enzenberger
<enz@cip.physik.uni-muenchen.de>. Copyright of the modifications
1997-1999.
Modified by Matthias Andree <matthias.andree@gmx.de>, Copyright 1999 -
2002. Modified by Ralf Wildenhues <ralf.wildenhues@gmx.de>, Copyright
2002.
Jonathan Larmour <jifl@jifvik.org> contributed the timeout_client feature.
Andreas Meininger <a.meininger@gmx.net> contributed the code to let
texpire ignore groupexpire = -1 groups.
Mark Brown <broonie@debian.org> added the noactive option.
Numerous contributions by other people.
The initial development of
leafnode has been paid for by Uninett AS
(
http://www.uninett.no/).
SEE ALSO¶
applyfilter(8),
checkgroups(8),
fetchnews(8),
newsq(1),
texpire(8).
tcpd(8),
hosts_access(5),
glob(7),
pcre(3),
RFC
977, RFC 2980.