Cron Manager

Implementation Steps

1. Understand Requirements

• What task needs to be scheduled?
• How frequently should it run?
• What time of day? (if applicable)
• Does the script already exist?

2. Create/Verify Script

• If script doesn't exist, create it
• Make it executable: chmod +x script.sh
• Test it manually first
• Ensure it uses absolute paths
• Add proper logging

3. Add to Crontab

# Edit user's crontab
crontab -e

# Or add directly
(crontab -l 2>/dev/null; echo "SCHEDULE COMMAND") | crontab -

4. Verify Installation

# List current cron jobs
crontab -l

# Check cron logs (if needed)
grep CRON /var/log/syslog

Best Practices

• Always use absolute paths in cron jobs
• Redirect output to log files for debugging
• Test scripts manually before adding to cron
• Add comments to crontab entries
• Use environment variables at top of crontab if needed
• Consider using flock to prevent overlapping executions

Example Cron Entries

# Backup database daily at 2am
0 2 * * * /home/user/scripts/backup_db.sh >> /var/log/backup.log 2>&1

# Clean temp files every 6 hours
0 */6 * * * find /tmp -type f -mtime +7 -delete

# System health check every 15 minutes
*/15 * * * * /home/user/scripts/health_check.sh

# Weekly report every Monday at 9am
0 9 * * 1 /home/user/scripts/weekly_report.sh

Troubleshooting

• Check cron service: systemctl status cron
• View user's crontab: crontab -l
• Check logs: grep CRON /var/log/syslog
• Verify script permissions and paths
• Test script execution manually
• Ensure script has no interactive prompts

Environment Notes

• Cron runs with minimal environment
• Set PATH explicitly if needed
• HOME, USER, LOGNAME are typically set
• Use cd in script if directory matters
• Export variables at top of crontab if needed

Removing Cron Jobs

# Edit and remove manually
crontab -e

# Remove all cron jobs
crontab -r

# Remove specific job programmatically
crontab -l | grep -v "pattern" | crontab -

Related Skills

• systemd-timer: Modern alternative to cron
• bash-automation: Create scripts for cron to run
• systemd-service: Long-running services vs scheduled tasks