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Rotate Log Files

Sometimes log files can become quite large. To prevent this, they should be "rotated" frequently.

logrotate is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compression, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large.

We cover the configuration of logrotate for the log files of a Tomcat 8 instance in this article, which are located in /home/www-data/example.ch/logs/catalina.out.

Configure Logrotate​

You will need to add a configuration file (e.g. as a hidden file in the home directory): ~/.logrotate.conf. A simple configuration might look like this:

~/.logrotate.conf
~/*/logs/catalina.out {
  daily
  rotate 14
  notifempty
  compress
  copytruncate

  compresscmd /usr/bin/zstdmt
  compressoptions -18 -T0 --rm -qq
  compressext .zst
  uncompresscmd /usr/bin/unzstd
}

With this configuration, logrotate:

  • rotates all files matching ~/*/logs/catalina.out once per day
  • keeps 14 log files
  • does not rotate if the file is empty
  • compresses the log files with ZSTD
  • copies the log file and empties the log file afterwards (copytruncate)

This will end up in daily log files like this:

  • .../catalina.out-20161212.zst
  • .../catalina.out-20161213.zst
  • .../catalina.out-20161214.zst

More configuration options can be found in the logrotate man page.

Execute Logrotate Daily​

Logrotate can be executed like this:

/usr/sbin/logrotate -s ~/.logrotate.status.tmp ~/.logrotate.conf

We have to provide a custom state file with the -s option, since the global state file is only writeable by the root user.

To execute this command daily, we should add it to the crontab by executing crontab -e. Simply add following line to the end of the file:

22 0 * * * /usr/sbin/logrotate -s ~/.logrotate.status.tmp ~/.logrotate.conf >/dev/null 2>&1

Now, the logrotate is executed once a day at 00:22. Be aware that with >/dev/null 2>&1 at the and of the command all output of the command is suppressed.

For more information on configuring cron, see the dedicated Cron Jobs documentation page.