Chapter 36. Log Files
Log files are files that contain
messages about the system, including the kernel, services, and
applications running on it. There are different log files for
different information. For example, there is a default system log
file, a log file just for security messages, and a log file for
Log files can be very useful when trying to troubleshoot a
problem with the system such as trying to load a kernel driver or
when looking for unauthorized log in attempts to the system. This
chapter discusses where to find log files, how to view log files,
and what to look for in log files.
Some log files are controlled by a daemon called syslogd. A list of log messages maintained by
syslogd can be found in the /etc/syslog.conf configuration file.
Most log files are located in the /var/log/ directory. Some applications such as
httpd and samba
have a directory within /var/log/ for
their log files.
You may notice multiple files in the log file directory with
numbers after them. These are created when the log files are
rotated. Log files are rotated so their file sizes do not become
too large. The logrotate package contains
a cron task that automatically rotates log files according to the
/etc/logrotate.conf configuration file
and the configuration files in the /etc/logrotate.d/ directory. By default, it is
configured to rotate every week and keep four weeks worth of
previous log files.