Cisco IOS Cookbook, 2nd Edition

Maintaining Syslog Files on the Server

Problem

You want to automatically rotate and archive router logfiles on a Unix server.

Solution

The Bourne shell script in Example 18-1 automatically rotates router logfiles to ensure that these files don’t become too big and cumbersome to navigate. The script is intended to be invoked via a cron job on a daily basis, but you can also run it manually. By default, the script retains seven days worth of archived logfiles and compresses files older than two days. No arguments are required or expected.

Example 18-1. rotatelog.sh

#!/bin/sh
#
#  rotatelog.sh -- a script to rotate logfiles and
#                  compress archived files 
#
# Set behavior    
SYSLOGPID=/etc/syslog.pid    
LOGDIR=/var/log
LOG=rtrlog
DAYS=7
COMPRESS="/usr/bin/compress -f"
#
# Program body
[ -f $SYSLOGPID ] || echo "Syslog PID file doesn't exist"
if [ -d $LOGDIR ]; then
  cd $LOGDIR
  [ -f $LOG.1 ] && \Q$COMPRESS $LOG.1\Q && sleep 1
  while [ $DAYS -gt 1 ]
  do
        LOW=\Qexpr $DAYS - 1\Q
        [ -f $LOG.$LOW.Z ] && mv $LOG.$LOW.Z $LOG.$DAYS.Z
        DAYS=$LOW
  done
[ -f $LOG ] || echo "Log file $LOG doesn't exist"
[ -f $LOG ] && mv $LOG $LOG.1
touch $LOG
chmod 644 $LOG
sleep 10
kill -HUP \Qcat $SYSLOGPID\Q
#
else
echo "Log directory $LOGDIR is not valid"
fi

Discussion

If left unchecked, the router logfiles grow until your disk space runs out. This script is designed to rotate router logfiles on a daily basis to ensure they don’t grow too large.

This script will rotate logs on a daily basis and retain seven days worth of archived ...