expire.ctl - Configuration file for article expiration

The file pathetc/expire.ctl is the default configuration file for expire and expireover, which read it at start-up. It serves two purposes: it defines how long history entries for expired or rejected articles are remembered, and it determines how long articles stored on the server are retained.

Normally, if all of the storage methods used by the server are self-expiring (such as CNFS), all lines except the CW/remember/ setting (described below) are ignored. This can be changed with the -N option to expire or expireover.

Black lines and lines beginning with a number sign (CW#) are ignored. All other lines should be in one of two formats. The order of the file is significant, and the last matching entry will be used.

The first format specifies how long to keep history entries for articles that aren't present in the news spool. These are articles that have either already expired, or articles which the server rejected (when remembertrash is set to true in inn.conf). There should be one and only one line in this format, which looks like:

    /remember/:<days>

where <days> is a decimal number that specifies the minimum number of days a history record for a given message ID is retained, regardless of whether the article is present in the spool. (History entries for articles still present in the spool are always retained.)

The primary reason to retain a record of old articles is in case a peer offers old articles that were previously accepted but have already expired. Without a history record for such articles, the server would accept the article again and readers would see duplicate articles. Articles older than a certain number of days won't be accepted by the server at all (see artcutoff in inn.conf(5) and the -c flag in innd(8)), and this setting should probably match that time period (10 days by default) to ensure that the server never accepts duplicates.

Most of the lines in this file will be in the second format, which consists of either four or five colon-separated fields:

    <pattern>:<flag>:<keep>:<default>:<purge>

if groupbaseexpiry is true in inn.conf (the default), and otherwise:

    <classnum>:<keep>:<default>:<purge>

All lines must be in the correct format given the current setting of groupbaseexpiry, and therefore the two formats cannot co-exist in the same file.

Normally, a rule matches a newsgroup through the combination of the <pattern> and <flag> fields. <pattern> is a uwildmat(3)-style pattern, specifying the newsgroups to which the line is applied. Note that the last matching entry will be used, so general patterns (such as defaults for all groups where <pattern> is CW*) should appear at the beginning of the file before more specific settings.

The <flag> field can be used to further limit newsgroups to which the line applies, and should be chosen from the following set:

    M   Only moderated groups
    U   Only unmoderated groups
    A   All groups
    X   Remove the article from all groups it appears in

Normally, articles are not completely deleted until they expire out of every group to which they were posted, but if an article is expired following a rule where <flag> is X, it is deleted out of all newsgroups to which it was posted immediately.

If groupbaseexpiry is instead set to false, there is no <pattern> and <flag> field and the above does not apply. Instead, there is a single <classnum> field, which is either a number matching the storage class number specified in storage.conf or CW* to specify a default for all storage classes. All articles stored in a storage class will be expired following the instructions in the line with a matching <classnum>, and when articles are expired, they're always removed from all groups to which they were posted.

The remaining three fields are the same in either format, and are used to determine how long an article should be kept. Each field should be either a decimal number of days (fractions like CW8.5 are allowed, but remember that articles are only removed when expire or expireover is run, normally once a day by news.daily) or the word CWnever.

The middle field, <default>, will be used as the expiration period for most articles. The other two fields, <keep> and <purge>, only come into play if the article requests a particular expiration date with an Expires header. Articles with an Expires header will be expired at the date given in that header, subject to the constraints that they will be retained at least <keep> days and no longer than <purge> days.

If <keep> is set to CWnever, no article matching that line will ever be expired. If <default> is set to CWnever, no article matching that line without an explicit Expires header will ever be expired. If <purge> is set to CWnever, Expires headers will be honored no matter how far into the future they are.

One should think of the fields as a lower bound, the default, and an upper bound. Since most articles do not have an Expires header, the second field is the most important and most commonly applied.

Articles that do not match any expiration rule will not be expired, but this is considered an error and will result in a warning. There should always be a default line (a line with a <pattern> of CW* and <flag> of CWA, or a line with a <classnum> of CW*), which can explicitly state that articles should never expire by default if that's the desired configuration. The default line should generally be the first line of the file (except for CW/remember/) so that other expiration rules can override it.

It is often useful to honor the Expires header in articles, especially those in moderated groups. To do this, set <keep> to zero, <default> to whatever normal expiration you wish, and <purge> to CWnever or some large number, like 365 days for a maximum article life of a year.

To ignore any Expires header, set all three fields to the same value.

When groupbaseexpiry is true (the default):

    # Keep expired article history for 10 days, matching artcutoff.
    /remember/:10

    # Most articles stay for two weeks, ignoring Expires.
    *:A:14:14:14

    # Accept Expires headers in moderated groups for up to a year and
    # retain moderated groups for a bit longer.
    *:M:1:30:365

    # Keep local groups for a long time and local project groups forever.
    example.*:A:90:90:90
    example.project.*:A:never:never:never

When groupbaseexpiry is false, for class-based expiration:

    # Keep expired article history for 10 days, matching artcutoff.
    /remember/:10

    # Set a default expiration of seven days.
    *:7:7:7

    # Class 0 is retained for two weeks.
    0:14:14:14

Written by Rich CW$alz <rsalz@uunet.uu.net> for InterNetNews. Converted to POD by Russ Allbery <rra@stanford.edu>.

$Id: expire.ctl.5,v 1.19 2003/04/06 21:50:06 rra Exp $

expire(8), expireover(8), inn.conf(5), innd(8), news.daily(8), storage.conf(5), uwildmat(3)