What is a Cron Job? How to Set Up Cron on Thai Hosting 2026

A Cron Job is a scheduled task that runs automatically at specified intervals on your hosting server. The name "cron" comes from the Greek word for time (chronos). Cron jobs are essential for automating repetitive tasks like database backups, email newsletters, sitemap updates, cache clearing, and log rotation — without any manual intervention.

Cron Expression Syntax

A cron expression consists of 5 time fields followed by the command to execute:

* * * * * command
| | | | |
| | | | └── Day of week (0=Sun, 1=Mon...6=Sat)
| | | └──── Month (1-12)
| | └────── Day of month (1-31)
| └──────── Hour (0-23)
└────────── Minute (0-59)

Use * for "any value", numbers for specific values, */n for "every n units", and commas for multiple values.

Common Cron Expression Examples

• 0 * * * * — Run every hour, at minute 0
• 0 2 * * * — Run daily at 2:00 AM
• 0 2 * * 0 — Run every Sunday at 2:00 AM
• 0 2 1 * * — Run at 2:00 AM on the 1st of each month
• */5 * * * * — Run every 5 minutes
• 0 9,17 * * 1-5 — Run at 9AM and 5PM, Monday through Friday

Creating Cron Jobs in DirectAdmin

1. Login to DirectAdmin → Advanced Features → Cron Jobs.
2. Fill in the Minute, Hour, Day, Month, Weekday fields and the Command.
3. Example — daily database backup at 2AM:
   /usr/bin/mysqldump -u dbuser -p'dbpass' dbname > /home/user/backup/db_$(date +\%Y\%m\%d).sql
4. Click Add Cron Job.

WordPress WP-Cron

WordPress has its own scheduling system called WP-Cron, which runs wp-cron.php every time a visitor loads a page. The problem: if your site has no visitors, scheduled tasks won't run.

Solution: Disable WP-Cron and create a real server cron job instead:

# In wp-config.php, add:
define('DISABLE_WP_CRON', true);

# Create a real cron job in DirectAdmin:
*/5 * * * * /usr/bin/php /home/user/public_html/wp-cron.php > /dev/null 2>&1

Popular Cron Job Use Cases

• Database backup: mysqldump every night at 2:00 AM
• Newsletter sending: Process email queue every 15 minutes
• Sitemap updates: Regenerate sitemap.xml every 6 hours
• Cache clearing: Remove expired cache files every hour
• Log rotation: Archive and delete old log files weekly
• SSL expiry check: Daily verification of certificate expiry dates
• Temp file cleanup: Remove temporary upload files daily

Troubleshooting Cron Jobs

• Wrong path: Always use absolute paths in cron (e.g., /usr/bin/php, not just php).
• Wrong permissions: Script files must have execute permission (chmod +x).
• Debug with logging: Add >> /tmp/cron.log 2>&1 to capture output for debugging.
• Environment differences: Cron runs in a minimal environment without the same PATH as your shell session.

Frequently Asked Questions