When setting up a cron job to run on the first day of each month, you need to understand the five time fields in crontab:

* * * * * command_to_execute
┬ ┬ ┬ ┬ ┬
│ │ │ │ └── Day of week (0-6) (0 is Sunday)
│ │ │ └──── Month (1-12)
│ │ └────── Day of month (1-31)
│ └──────── Hour (0-23)
└────────── Minute (0-59)

For a job that runs at midnight on the first day of every month:

0 0 1 * * /path/to/your/script.sh

This breaks down as:

• Minute: 0 (top of the hour)
• Hour: 0 (midnight)
• Day of month: 1 (first day)
• Month: * (every month)
• Day of week: * (ignored when day of month is specified)

1. Environment Variables

Cron jobs run with a minimal environment. Always specify full paths:

0 0 1 * * /usr/bin/python3 /home/user/scripts/monthly_report.py

2. Permission Issues

Ensure your script is executable:

chmod +x /path/to/your/script.sh

3. Logging for Debugging

Redirect output to a log file:

0 0 1 * * /path/to/script.sh >> /var/log/monthly_job.log 2>&1

Using @monthly Special String

Some cron implementations support:

@monthly /path/to/script.sh

This runs at midnight on the first day of each month.

Systemd Timers (Modern Linux Systems)

Create a timer unit file:

[Unit]
Description=Monthly job

[Timer]
OnCalendar=*-*-01 00:00:00
Persistent=true

[Install]
WantedBy=timers.target

Check system logs to confirm execution:

grep CRON /var/log/syslog

Or test with a temporary job that runs sooner:

* * * * * /path/to/test_script.sh

#!/usr/bin/env python3
import datetime
import sys

try:
    # Your monthly tasks here
    print(f"Monthly job executed at {datetime.datetime.now()}")
except Exception as e:
    print(f"Error: {str(e)}", file=sys.stderr)
    sys.exit(1)

Configure in crontab:

0 0 1 * * /usr/bin/python3 /path/to/monthly.py >> /var/log/monthly.log 2>&1

---

Cron jobs are scheduled using a specific syntax with five time fields followed by the command to execute:

* * * * * command_to_execute
┬ ┬ ┬ ┬ ┬
│ │ │ │ └── Day of the week (0 - 6) (Sunday=0)
│ │ │ └──── Month (1 - 12)
│ │ └────── Day of the month (1 - 31)
│ └──────── Hour (0 - 23)
└────────── Minute (0 - 59)

To run a job on the first day of every month at midnight, use:

0 0 1 * * /path/to/your/script.sh

This breaks down as:

• Minute: 0 (top of the hour)
• Hour: 0 (midnight)
• Day: 1 (first day of month)
• Month: * (every month)
• Day of week: * (ignored when day of month is specified)

Here are some common use cases with complete examples:

1. Database Backup

0 0 1 * * /usr/bin/mysqldump -u root -pPASSWORD database_name > /backups/db_$(date +\%Y\%m\%d).sql

2. Log Rotation

0 0 1 * * /usr/sbin/logrotate /etc/logrotate.d/myapp

3. Monthly Report Generation

0 0 1 * * /usr/bin/python3 /scripts/generate_monthly_report.py

If your cron job isn't working:

1. Check system logs: grep CRON /var/log/syslog
2. Verify the command works when run manually
3. Ensure the script has execute permissions
4. Use absolute paths in your commands
5. Check the user's environment variables

For more complex scheduling needs:

# Run on first weekday of month (Mon-Fri)
0 0 1-7 * * [ "$(date +\%u)" -le 5 ] && /path/to/command

# Run on first Monday of month
0 0 1-7 * * [ "$(date +\%u)" -eq 1 ] && /path/to/command