Cron jobs are useful for automating tasks on your server, but running them too frequently can consume server resources and impact performance. To prevent this, you can create a bash script that enforces a minimum interval between cron job executions. In this guide, we'll show you how to create a script called `cronlimit.sh` that limits the frequency of cron jobs to a minimum of 16 minutes.
Step 1: Create the `cronlimit.sh` script
1. Log in to your server as the root user.
2. Navigate to the `/usr/bin` directory by running the command `cd /usr/bin`.
3. Create a new file called `cronlimit.sh` using a text editor like `vi` or `nano`.
4. Copy and paste the following script into the file:
min=16 # the minimum allowed interval between runs
for crontab in /var/spool/cron/*
# replace the * * * * * jobs with */16 * * * * jobs.
sed -i "s/\* \* \* \* \*/\*\/16 * * * */" $crontab
for i in `seq 1 $min`
# replace */N * * * * for every N <= min
sed -i "s/\*\/$i \* \* \* \*/*\/16 * * * */" $crontab
5. Save the file and exit the text editor.
6. Make the script executable by running the command `chmod +x /usr/bin/cronlimit.sh`.
Step 2: Add the `cronlimit.sh` script to the root user's crontab
1. Open the root user's crontab file located in `/var/spool/cron/root` using a text editor like `vi` or `nano`.
2. Add the following line to the bottom of the file:
*/16 * * * * /usr/bin/cronlimit.sh
3. Save the file and exit the text editor.
By creating and configuring the `cronlimit.sh` script, you've enforced a minimum interval of 16 minutes between cron job executions. This helps to prevent excessive resource usage and maintain optimal server performance. Remember to adjust the minimum interval as needed for your specific requirements.