How to set maximum log file size with Logrotate

Configure Logrotate to rotate a log file when it exceeds a specified size threshold.

Prerequisites

• Linux system with Logrotate installed.
• Root or sudo access to edit files in /etc/logrotate.d/.
• An existing Logrotate configuration file for the target application.

Step-by-Step: Set Maximum Log File Size with Logrotate

1. Open the Logrotate configuration file for the target application. This example uses Nginx:

   sudo nano /etc/logrotate.d/nginx

2. Add the size directive inside the log file block. Logrotate rotates the file when it exceeds the specified size:

   /var/log/nginx/*.log {
       size 100M
       rotate 7
       compress
       missingok
       notifempty
   }

   Logrotate accepts size values in bytes (default), kilobytes ( k), megabytes ( M), and gigabytes ( G). The value 100M triggers rotation when the log file exceeds 100 megabytes.

   

   The size directive overrides time-based directives ( daily, weekly, monthly). Logrotate ignores the schedule and rotates based on file size alone.

3. Save the configuration file and exit the editor.

4. Test the updated Logrotate configuration in debug mode:

   sudo logrotate -d /etc/logrotate.d/nginx

   Logrotate shows whether each file meets the size threshold for rotation.

How to Verify Maximum File Size Rotation Works

Logrotate checks the file size on its next scheduled run. Force an immediate check to verify:

sudo logrotate -vf /etc/logrotate.d/nginx

Logrotate rotates files that exceed the configured size and prints verbose output confirming the action.

Common Issues When Setting Maximum Log File Size with Logrotate

Log files are not rotated despite exceeding the size.Logrotate checks file sizes only when it runs. The default cron job runs once per day. A rapidly growing log file may exceed the size limit between runs. For more frequent checks, create a custom cron job that runs Logrotate hourly with a separate state file.

The size directive conflicts with time-based directives.The size directive takes precedence over daily, weekly, or monthly. To combine both conditions, use maxsize instead. Logrotate rotates when the file exceeds maxsize even if the time interval has not elapsed. Use minsize to require both the time interval AND a minimum file size before rotation.

For a full reference of all Logrotate directives, see the Logrotate directives reference.