Log management and rotation in Jenkins - Commands & Configuration

Introduction

Jenkins creates log files to record what happens during builds and system operations. Over time, these logs can grow large and use up disk space. Log management and rotation help keep logs organized and prevent disk space from filling up by automatically archiving or deleting old logs.

When Jenkins server disk space is running low due to large log files

When you want to keep only recent build logs and remove older ones automatically

When you need to archive logs for a certain period for auditing but not keep them forever

When you want to improve Jenkins performance by limiting log file size

When you want to avoid manual cleanup of Jenkins logs

Config File - jenkins.xml

jenkins.xml

<?xml version="1.0" encoding="UTF-8"?>
<jenkins>
  <logRotator>
    <daysToKeep>30</daysToKeep>
    <numToKeep>50</numToKeep>
    <artifactDaysToKeep>-1</artifactDaysToKeep>
    <artifactNumToKeep>-1</artifactNumToKeep>
  </logRotator>
</jenkins>

This configuration sets Jenkins to keep build logs for 30 days or up to 50 builds, whichever limit is reached first. The daysToKeep tag controls how many days logs are kept. The numToKeep tag controls how many builds' logs are kept. Negative values mean unlimited. This helps Jenkins automatically delete old logs and save disk space.

Commands

Starts the Jenkins server on port 8080 so you can access the web interface to configure jobs and log rotation.

Terminal

java -jar jenkins.war --httpPort=8080

Expected Output

Running from: /home/jenkins/jenkins.war

INFO: Jenkins is fully up and running

→

--httpPort=8080 - Sets the HTTP port Jenkins listens on

Uploads a job configuration XML file that includes log rotation settings to Jenkins for the job named 'my-job'. This sets how many build logs to keep.

Terminal

curl -X POST http://localhost:8080/job/my-job/config.xml --data-binary @config.xml -H "Content-Type: text/xml"

Expected Output

No output (command runs silently)

Checks the current log rotation settings for the 'my-job' Jenkins job to verify they are applied.

Terminal

curl http://localhost:8080/job/my-job/api/xml?xpath=//logRotator

Expected Output

<logRotator>

  <daysToKeep>30</daysToKeep>

  <numToKeep>50</numToKeep>

  <artifactDaysToKeep>-1</artifactDaysToKeep>

  <artifactNumToKeep>-1</artifactNumToKeep>

</logRotator>

Lists the build directories and their sizes to see how much disk space the logs are using after rotation settings.

Terminal

ls -lh /var/lib/jenkins/jobs/my-job/builds/

Expected Output

drwxr-xr-x 3 jenkins jenkins 4.0K Jun  1 12:00 1

 drwxr-xr-x 3 jenkins jenkins 4.0K Jun  2 12:00 2

 drwxr-xr-x 3 jenkins jenkins 4.0K Jun  3 12:00 3

→

-lh - Lists files with human-readable sizes

Key Concept

If you remember nothing else from this pattern, remember: configuring log rotation in Jenkins keeps your disk clean by automatically deleting old build logs.

Common Mistakes

Not setting any log rotation policy in Jenkins job configuration

Logs will accumulate indefinitely, filling disk space and slowing Jenkins

Always configure daysToKeep or numToKeep in the job's logRotator section

Setting both daysToKeep and numToKeep to very high or unlimited values

This defeats the purpose of log rotation and can cause disk space issues

Set reasonable limits based on your storage and audit needs

Forgetting to reload or restart Jenkins after changing config files manually

Changes won't take effect until Jenkins reloads configuration

Reload configuration from disk or restart Jenkins after manual edits

Summary

Start Jenkins server to manage jobs and logs.

Configure log rotation in job XML to limit how many build logs are kept.

Verify log rotation settings via Jenkins API or UI.

Check disk usage of build logs to confirm rotation is working.