This directory is more popularly known as $NEWSCTL. It contains configuration, log and status files. There are no articles or binaries kept here. Let's see what some of the files are meant for. Control files are dealt in slightly greater detail in "Section 4.3>"
sys: One line per system/NDN listing all the newsgroup hierarchies each system subscribes to. Each line is prefixed with the system name and the one beginning with ME: indicates what we are going to receive. Look up manpage of newssys.
explist: This file has entries indicating articles of which newsgroup expire and when and if they have to be archived. The order in which the newsgroups are listed is important. See manpage of expire for file format.
batchparms: Details of how to feed other sites/NDN, like the size of batches, the mode of transmission (UUCP/NNTP) are specified here. manpage to refer: newsbatch.
controlperm: If you wish to authenticate a control message before any action is taken on it, you must enter authentication-related information here. The controlperm manpage will list all the fields in detail.
mailpaths: It features the e-mail address of the moderator for each newsgroup who is responsible for approving/disapproving articles posted to moderated newsgroups. The sample mailpaths file in the tar will give you an idea of how entries are made.
nntp_access/user_access: These files contain entries of servernames and usernames on whom restrictions will apply when accessing newsgroups. Again, the sample file in the tarball shall explain the format of the file.
log, errlog: These are log files that keep growing large with each batch that is received. The log file has one entry per article telling you if it has been accepted by your news server or rejected. To understand the format of this file, refer to Chapter 2.2 of the CNews guide. Errors, if any, while digesting the articles are logged in errlog. These log files have to be rolled as the files hog a lot of disk space.
nntplog: This file logs information of the nntpd giving details of when a connection was established/broken and what commands were issued. This file needs to be configured in syslog syslogd should be running.
active: This file has one line per newsgroup to be found in your news server. Besides other things, it tells you how many articles are currently present in each newsgroup. It is updated when each batch is digested or when articles are expired. The active manpage will furnish more details about other paramaters.
history: This file, again, contains one line per article, mapping message-id to newsgroup name and also giving its associated article number in that newsgroup. It is updated each time a feed is digested and when doexpire is run. Plays a key role in loop-detection and serves as an article database. Read manpage of newsdb, doexpire for the file format
newsgroups: It has a one-line description for each newsgroup explaining what kind of posts go into each of them. Ideally speaking, it should cover all the newsgroups found in the active file.
Miscellaneous files: Files like mailname, organisation, whoami contain information required for forming some of the headers of an article. The contents of mailname form the From: header and that of organisation form the Organisation: header. whoami contains the name of the news system. Refer to chapter 2.1 of guide.ps for a detailed list of files in the $NEWSCTL area. Read RFC 1036 for description of article headers .
>newsgroup directories: For each newsgroup hierarchy that the news server has subscribed to, a directory is created under $NEWSARTS. Further sub-directories are created under the parent to hold articles of specific newsgroups. For instance, for a newsgroup like comp.music.compose, the parent directory comp will appear in $NEWSARTS and a sub-directory called music will be created under comp. The music sub-directory shall contain a further sub-directory called compose and all articles of comp.music.compose shall reside here. In effect, article 242 of newsgroup comp.music.compose shall map to file $NEWSARTS/comp/music/compose/242.
control: The control directory houses only the control messages that have been received by this site. The control messages could be any of the following: newgroup, rmgroup, checkgroup and cancel appearing in the subject line of the article. More information to be found in "Section 2.4>"
junk: The junk directory contains all articles that the news server has received and has decided, after processing, that it does not belong to any of the hierarchies it has subscribed to. The news server transfers/passes all articles in this directory to NDNs that have subscribed to the junk hierarchy.