Linux Network Administrator Guide, Second Edition

that this rule applies only to moderated newsgroups, a U to mean that this rule applies only to unmoderated newsgroups, or an A to mean that this rule ignores the moderated status and applies to all groups.

keep

This field allows you to specify the minimum time an article with an 'Expires' header will be kept before it is expired. The units are days, and are a floating point, so you may specify values like 7.5 for seven-and-a-half days. You may also specify never if you wish articles to stay in a newsgroup forever.

default

This field is the most important. This field allows you to specify the time an article without an Expires header will be kept. Most articles won't have an Expires header. This field is coded in the same way as the keep field, with never meaning that articles without Expires headers will never be expired.

purge

This field allows you to specify the maximum time an article with an Expires header will be kept before it is expired. The coding of this field is the same as for the keep field.

Our requirements are simple. We will keep all articles in all newsgroups for 14 days by default, and between 7 and 21 days for articles that have an Expires header. The rec.crafts.brewing.private newsgroup is our internal newsgroup, so we'll make sure we don't expire any articles from it:

# expire.ctl file for the Virtual Brewery
# Expire all articles in 14 days by default, 7-21 days for those with
# Expires: headers
*:A:7:14:21
# This is a special internal newsgroup, which we will never expire.
rec.crafts.brewing.private:A:never:never:never

We will mention one special type of entry you may have in your /etc/news/expires.ctl file. You may have exactly one line that looks like this:

/remember/:days

This entry allows you to specify the minimum number of days that an article will be remembered in the history file, irrespective of whether the article itself has been expired or not. This might be useful if one of the sites that is feeding you articles is infrequent and has a habit of sending you old articles every now and again. Setting the /remember/ field helps to prevent the upstream server from sending you the article again, even if it has already been expired from your server. If your server remembers it has already received the article, it will reject attempts to resend it. It is important to remember that this setting has no effect at all on article expiration; it affects only the time that details of an article are kept in the history database.

Handling Control Messages

Just as with C News, INN can automatically process control messages. INN provides a powerful configuration mechanism to control what action will occur for each of a variety of control messages, and an access control mechanism to control who can initiate actions against which newsgroups.

The control.ctl file

The control.ctl file is fairly simple in structure. The syntax rules for this file are much the same as for the other INN configuration files. Lines beginning with # are ignored, lines may be continued using /, and fields are delimited by:.

When a control message is received, it is tested against each rule in turn. The last rule in the file that matches the message is the rule that will be used, so you should put any generic rules at the start of the file and more specific rules at the end of the file. The general syntax of the file is:

message:from:newsgroups:action

The meanings of each of the fields are:

message

This is the name of the control message. Typical control messages are described later.

from

This is a shell-style pattern matching the email address of the person sending the message. The email address is converted to lowercase before comparison.

newsgroups

If the control message is newgroup or rmgroup, this field is a shell-style pattern matching the newsgroup created or removed.

action

This field specifies what action to take for any message matching the rule. There are quite a number of actions we can take; they are described in the next list.

The message field of each line can have one of the following values:

checkgroups

This message requests that news administrators resynchonrize their active newsgroups database against the list of newsgroups supplied in the control message.

newgroup

This message requests the creation of a new newsgroup. The body of the control message should contain a short description of the purpose of the newsgroup to be created.

rmgroup

requests that a newsgroup be removed.

sendsys

This message requests that the sys file of this news server be transmitted by mail to the originator of the control message. RFC-1036 states that it is a requirement of Usenet membership that this information be publicly available because it is used to keep the map of Usenet up to date.

version

This message requests that the hostname and version of news server software be returned to the originator of the control message.

all

This is a special coding that will match any control message.

The message field may include the following actions:

doit

The requested command is performed. In many cases, a mail message will be sent to the administrator to advise them that the action has taken place.

doit=file

This is the same as the doit action except that a log message will be written to the file log file. If the specified file is mail, the log entry is sent by email. If the specified file is the null string, the log message is written to /dev/null and is equivalent to using the unqualified doit action. If the file name begins with a / character, the name is taken to be an absolute filename for the logfile; otherwise, the specified name is translated to /var/log/news/file.log.