运维脚本编程基础

手动 SSH 改配置、逐台重启服务无法 scale。Bash / Python 脚本 把重复运维动作自动化：批量查端口、备份邮件队列、DNS 变更验证、健康检查。本课不要求成为开发，但需能 读、改、写 50 行以内的实用脚本。版本管理见 git-essentials，Linux 基础见 linux-essentials，网络排查见 networking-essentials，DNS 验证见 dns-essentials。

学习目标

• 编写带 set -euo pipefail 的健壮 Bash 脚本
• 用 Python 调用 subprocess / socket 做端口与 SMTP 探测
• 将脚本纳入 Git 仓库并与 cron/systemd timer 集成

Bash 脚本模板

#!/bin/bash
# check-mail-ports.sh — 检查邮件相关端口是否监听
set -euo pipefail

PORTS=(25 587 993)
HOST="${1:-127.0.0.1}"

for port in "${PORTS[@]}"; do
  if ss -tln | grep -q ":${port} "; then
    echo "OK  ${HOST}:${port} listening"
  else
    echo "FAIL ${HOST}:${port} not listening" >&2
    exit 1
  fi
done

chmod +x check-mail-ports.sh
./check-mail-ports.sh
./check-mail-ports.sh 192.168.1.10

常用运维脚本模式

备份 Postfix 队列

#!/bin/bash
set -euo pipefail
BACKUP_DIR="/var/backups/postfix"
DATE=$(date +%Y%m%d-%H%M%S)
mkdir -p "$BACKUP_DIR"
tar czf "${BACKUP_DIR}/spool-${DATE}.tar.gz" /var/spool/postfix
find "$BACKUP_DIR" -name 'spool-*.tar.gz' -mtime +7 -delete
echo "Backup done: spool-${DATE}.tar.gz"

DNS 传播检查

#!/bin/bash
set -euo pipefail
DOMAIN="${1:?usage: $0 example.com}"
for resolver in 8.8.8.8 1.1.1.1; do
  echo "=== $resolver ==="
  dig TXT "$DOMAIN" @"$resolver" +short | grep -i spf || echo "(no SPF)"
done

Python：SMTP 探测

#!/usr/bin/env python3
"""smtp_probe.py — 测试 SMTP Submission 端口"""
import socket
import sys

def probe(host: str, port: int = 587, timeout: float = 5.0) -> bool:
    try:
        with socket.create_connection((host, port), timeout=timeout):
            print(f"OK  {host}:{port} reachable")
            return True
    except OSError as e:
        print(f"FAIL {host}:{port} — {e}", file=sys.stderr)
        return False

if __name__ == "__main__":
    host = sys.argv[1] if len(sys.argv) > 1 else "localhost"
    sys.exit(0 if probe(host) else 1)