From : http://www.derkeiler.com/Mailing-Lists/securityfocus/bugtraq/2005-01/0295.html
Date: Tue, 25 Jan 2005 16:21:44 +0200 (EET) To: BUGTRAQ
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I’m sorry, if this is old news to you, but I couldn’t find similar cases in BUGTRAQ archives.
logwatch (www.logwatch.org) is widely recommended tool for creating nice reports of various, often security related logfiles. logwatch is included at least in recent Red Hat/Fedora linux distributions, probably others as well.
logrotate script is used to periodically rotate and delete logfiles.
Default configuration in recent Red Hat/Fedora distributions is following:
run logwatch daily (from /etc/cron.daily, starting at 04:02) using range ‘yesterday’ and skipping log archives (i.e. secure.1)
run logrotate daily (from /etc/cron.daily, after logwatch) using rotation period ‘weekly’, practically every Sunday morning
Above defaults create blind spot every Sunday morning between 00:00:00 - 04:01:59 (system local time), when entries added to any system logs are discarded from logwatch reports.
Situation is even worse on a busy server, in case you need to rotate some or all logfiles daily. In that case, the blind spot happens every day.
This is a problem only for organizations or system administrators relying solely on logwatch reports, as all logged information is still present in system logs.
There are some ways to make logwatch reports more reliable:
set “Archives = yes” in logwatch.conf. You might also want to tune archive settings in /etc/log.d/conf/logfiles/ to prevent unnecessary processing of really old archives. To cover the blind spot with range ‘yesterday’ and weekly rotation, it is usually enough to specify for example “Archive = secure.1” in secure.conf
move logwatch and logrotate to happen at midnight
change date matching logic in /etc/log.d/scripts to match for example previous 24 hours
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