Crontab 치트 시트 2025: 실제로 사용하는 50+ Cron 표현식 예제

백업 예약, 배포 자동화, 정기 정리 스크립트 실행 등 cron은 Unix/Linux 시스템의 태스크 스케줄링 핵심입니다. 이 치트시트는 50개 이상의 복사 가능한 cron 표현식 예시를 빈도별로 제공합니다.

1. Cron 표현식 구문

표준 cron 표현식은 공백으로 구분된 5개 필드로 구성됩니다:

┌───────────── 분 (0–59)
│ ┌─────────── 시 (0–23)
│ │ ┌───────── 일 (1–31)
│ │ │ ┌─────── 월 (1–12)
│ │ │ │ ┌───── 요일 (0–7)
│ │ │ │ │
* * * * *  command_to_execute

명령어는 5개 필드 뒤에 옵니다. Cron 생성기 도구로 시각적으로 구성할 수 있습니다.

2. 특수 문자

Cron은 4개의 특수 문자를 사용합니다:

3. 50개 이상의 Cron 표현식 예시

가장 많이 사용되는 cron 스케줄을 담은 표입니다.

X분마다

매시

매일

매주

매월

매년/분기별

비즈니스 & DevOps

4. Crontab 명령어

crontab 명령어로 사용자별 cron 파일을 관리합니다:

# Edit crontab
crontab -e

# List all cron jobs
crontab -l

# Backup current crontab to a file
crontab -l > my-crontab-backup.txt

# Install crontab from a file
crontab my-crontab-backup.txt

# Remove all cron jobs (careful!)
crontab -r

5. 플랫폼별 구문

Cron 구문은 플랫폼마다 다릅니다:

# Standard 5-field crontab
*/5 * * * * /usr/local/bin/backup.sh >> /var/log/backup.log 2>&1

# .github/workflows/scheduled.yml
on:
  schedule:
    - cron: '0 9 * * 1-5'  # Weekdays 9AM UTC

# AWS EventBridge (6 fields, note the ?)
cron(0 9 ? * MON-FRI *)  # Weekdays 9AM UTC

# Kubernetes CronJob spec
apiVersion: batch/v1
kind: CronJob
metadata:
  name: daily-backup
spec:
  schedule: "0 2 * * *"
  timeZone: "America/New_York"  # K8s 1.27+

// vercel.json
{
  "crons": [{
    "path": "/api/cron/daily-report",
    "schedule": "0 9 * * *"
  }]
}

6. 자주 하는 실수

Cron에서 가장 흔한 실수:

# Gotcha: overlapping runs - use flock to prevent
*/5 * * * * /usr/bin/flock -n /tmp/myjob.lock /path/to/script.sh

# Gotcha: environment - always use full paths
0 2 * * * /usr/bin/python3 /home/user/scripts/backup.py >> /var/log/backup.log 2>&1

# Gotcha: 30-second workaround (two entries)
* * * * * /path/to/script.sh
* * * * * sleep 30 && /path/to/script.sh

# Gotcha: PATH not set - define it at the top of your crontab
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

# Gotcha: percent signs (%) must be escaped in crontab
# Wrong:
0 0 * * * echo "Today is $(date +%Y-%m-%d)"
# Correct:
0 0 * * * echo "Today is $(date +\%Y-\%m-\%d)"

Sample Crontab File

Here is a complete, real-world crontab file combining several patterns discussed above:

# =============================================
# Crontab for: webserver (production)
# Last updated: 2025-01-15
# =============================================

# Environment
SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
MAILTO="ops-team@example.com"

# --- BACKUPS ---
# Full database backup at 2:00 AM daily
0 2 * * * /usr/bin/flock -n /tmp/db-backup.lock /opt/scripts/db-backup.sh >> /var/log/db-backup.log 2>&1

# Incremental file backup every 6 hours
0 */6 * * * /opt/scripts/file-backup.sh >> /var/log/file-backup.log 2>&1

# --- MAINTENANCE ---
# Clear temp files older than 7 days, daily at 3 AM
0 3 * * * /usr/bin/find /tmp -type f -mtime +7 -delete

# Rotate application logs every Sunday at 4 AM
0 4 * * 0 /opt/scripts/rotate-logs.sh >> /var/log/log-rotation.log 2>&1

# --- MONITORING ---
# Health check every 5 minutes
*/5 * * * * /opt/scripts/healthcheck.sh > /dev/null 2>&1

# SSL certificate expiry check daily at 6 AM
0 6 * * * /opt/scripts/check-ssl.sh

# Disk space alert if usage > 90%, every hour
0 * * * * /opt/scripts/disk-alert.sh

# --- REPORTS ---
# Send daily summary at 8 AM on weekdays
0 8 * * 1-5 /opt/scripts/daily-report.sh

# Monthly analytics report on the 1st at 9 AM
0 9 1 * * /opt/scripts/monthly-report.sh

7. 테스트 및 디버그

프로덕션 배포 전:

# Redirect all output to a log file
0 2 * * * /path/to/backup.sh >> /var/log/cron-backup.log 2>&1

# Disable cron mail for this job
0 2 * * * /path/to/backup.sh > /dev/null 2>&1

# Set MAILTO at the top of crontab
MAILTO=""
# Or send to a real address
MAILTO="admin@example.com"

# Check cron logs on Debian/Ubuntu
grep CRON /var/log/syslog | tail -20

# Check cron logs on CentOS/RHEL
grep CRON /var/log/cron | tail -20

# On systems using journald (systemd)
journalctl -u cron --since "1 hour ago"

# Quick test: add a job that writes to a file
# Then check if the file gets updated
* * * * * echo "cron works: $(date)" >> /tmp/cron-test.log

# Verify your crontab was saved correctly
crontab -l | grep -v '^#'

# Check if cron daemon is running
systemctl status cron    # Debian/Ubuntu
systemctl status crond   # CentOS/RHEL

Common Cron Debugging Checklist

8. 자주 묻는 질문