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Packages, services, and logs / Stage 12 of 13

Log rotation and retention

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Step 1 of 9 · on a machine · 5 min

The rule is there, the log is unchanged

What you will learn

  • Read a logrotate rule and tell a rotation plan from a performed rotation.
  • Limit the space the systemd journal takes and free it.
  • Rotate a log so that the program keeps writing to the new one.

The application log /var/log/lab-rotate/app.log has grown, and a rotation rule was written for it. A colleague ran logrotate with the --debug option "to see the details" and is sure the rotation happened. Repeat after them and compare the directory before and after.

Exercise · look

Rotation with --debug

You are in /srv/rotate-lab. Look at the log directory, run logrotate the way your colleague did, and look at the directory again.

First, predict

logrotate will print log needs rotating and renaming /var/log/lab-rotate/app.log to /var/log/lab-rotate/app.log.1. What will the directory hold after the command?

Now start the exercise, run the command and compare your prediction with the output.

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Check yourself 1 question

Why did logrotate describe renaming app.log, while the files in the directory did not change?

  • logrotate printed log needs rotating: 2048 bytes is over the size 1k threshold.

  • The timer runs logrotate with the system rules in /etc/logrotate.d. The rule in /srv/rotate-lab is not among them.

  • The command ran through sudo, and the output has no permission errors. On its first line logrotate itself says it does nothing in debug mode.

--debug only showed the rotation plan, as logrotate warned on its first line.

Found an inaccuracy? Report an error in the lesson

Ubuntu 24.04
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