log_truncation_guide.md

Log Truncation Utility with systemd

This document explains how to set up and use a log truncation utility on a Linux system using systemd

Setup

Step 1: Script Creation

1. Create the Script (truncate_logs.sh):

   Copy the following script into a new file named truncate_logs.sh. This script searches for log files larger than a specified size and truncates them if they were modified in the last 30 minutes. Add the file in /usr/local/sbin/.

   #!/bin/bash
   
   # Define the directory containing the logs and the size threshold
   LOG_DIR="/var/log"
   MAX_SIZE=100M # Max size in MB, modify as needed
   
   # Find and truncate to 100M the files larger than the specified size.
   find $LOG_DIR -type f -size +$MAX_SIZE -exec truncate -s 100M {} \;

2. Make the Script Executable:

   Run the following command to make the script executable:

   sudo chmod +x /usr/local/sbin/truncate_logs.sh

Step 2: systemd Service File Creation

1. Create the Service File (truncate_logs.service):

   Create a new file named truncate_logs.service in /etc/systemd/system/ with the following content:

   [Unit]
   Description=Log Truncation Service
   
   [Service]
   Type=oneshot
   ExecStart=/usr/local/sbin/truncate_logs.sh
   
   [Install]
   WantedBy=multi-user.target

2. Reload systemd and Enable the Service:

   Run the following commands to reload systemd and enable the service:

   sudo systemctl daemon-reload
   sudo systemctl enable truncate_logs.service

Step 3: systemd Timer File Creation (Optional)

1. Create the Timer File (truncate_logs.timer):

   If you want the script to run automatically at regular intervals (e.g., every half hour), create a file named truncate_logs.timer in /etc/systemd/system/ with the following content:

   [Unit]
   Description=Run log truncation every half hour
   
   [Timer]
   # execute log_truncate service each 30 minutes
   OnCalendar=*:0/30
   Persistent=true
   
   [Install]
   WantedBy=timers.target

2. Enable and Start the Timer:

   Run these commands to enable and start the timer:

   sudo systemctl enable truncate_logs.timer
   sudo systemctl start truncate_logs.timer

Usage

Once set up, the script will run according to the schedule defined in the truncate_logs.timer file (every 30 minutes in this case). You can also manually trigger the script by starting the truncate_logs.service:

sudo systemctl start truncate_logs.service

Customization

• Log Directory and Size Threshold: Modify the LOG_DIR and MAX_SIZE variables in the truncate_logs.sh script to suit your requirements.
• Schedule: Adjust the OnCalendar setting in the truncate_logs.timer file to change the script's execution schedule.