Linux 服务管理与日志

systemctl status nginx                                # ⭐ 看一个服务的运行状态
systemctl is-active nginx                             # 只输出 active / inactive
systemctl is-enabled nginx                            # 是否开机自启
systemctl list-units --type=service                   # 列出所有运行中的服务
systemctl list-units --type=service --state=failed    # 列出挂掉的服务
systemctl list-unit-files --type=service              # 列出所有定义过的服务（含未启用）

● nginx.service - A high performance web server
     Loaded: loaded (/lib/systemd/system/nginx.service; enabled; ...)
     Active: active (running) since Wed 2026-05-02 10:00:00 UTC; 2h ago
   Main PID: 1234 (nginx)
      Tasks: 3 (limit: 4915)
     Memory: 12.3M
        CPU: 215ms
     CGroup: /system.slice/nginx.service
             ├─1234 nginx: master process /usr/sbin/nginx
             └─1235 nginx: worker process

May 02 10:00:00 web01 systemd[1]: Started A high performance web server.
May 02 10:00:01 web01 nginx[1234]: configuration test successful

sudo systemctl start nginx              # 启动
sudo systemctl stop nginx               # 停止
sudo systemctl restart nginx            # 重启（先 stop 再 start，会有短暂中断）
sudo systemctl reload nginx             # 平滑重载配置（不中断，仅部分服务支持）
sudo systemctl reload-or-restart nginx  # 优先 reload，不支持则 restart

sudo systemctl enable nginx           # 设置开机自启（不会立即启动）
sudo systemctl enable --now nginx     # ⭐ 同时立即启动 + 设置自启
sudo systemctl disable nginx          # 取消开机自启（不会停止当前进程）
sudo systemctl disable --now nginx    # 同时立即停止 + 取消自启

sudo systemctl daemon-reload          # ⭐ 重新加载所有 unit 文件配置
sudo systemctl restart myapp          # 然后重启服务让新配置生效

journalctl -u nginx                          # 看 nginx 服务的所有日志
journalctl -u nginx -n 100                   # -n 最近 100 行
journalctl -u nginx -f                       # ⭐ 实时跟踪（tail -f 的 systemd 版）
journalctl -u nginx --since "10 min ago"     # 最近 10 分钟
journalctl -u nginx --since "2026-05-02 10:00"
journalctl -u nginx --since today
journalctl -u nginx -p err                   # -p = priority，只看 error 级别
journalctl -u nginx --no-pager               # 不分页直接输出（脚本里用）
journalctl -xe                               # 看系统级最近错误（启动失败常用）

tail -f /var/log/nginx/error.log              # 应用日志
tail -f /var/log/nginx/error.log | grep ERROR # 只看 ERROR
tail -f -n 100 app.log                        # 先显示最后 100 行再实时跟

sudo systemctl restart myapp
sudo systemctl status myapp                  # 看是否 active
journalctl -u myapp -n 50 --no-pager         # 没起来就看日志
tail -f /var/log/nginx/error.log             # 反代的错也要看

# 1. 登录后看清状况
ssh deploy@web01
pwd && whoami && uname -a
df -h && free -h

# 2. 安装依赖
sudo apt update
sudo apt install -y nginx python3 python3-pip git

# 3. 上传/拉取代码
cd /opt
sudo git clone https://github.com/me/myapp.git
sudo chown -R deploy:deploy /opt/myapp
cd /opt/myapp

# 4. 装 Python 依赖
pip3 install -r requirements.txt

# 5. 写 systemd 服务
sudo vim /etc/systemd/system/myapp.service       # 按 2.6 章模板
sudo systemctl daemon-reload
sudo systemctl enable --now myapp

# 6. 检查
sudo systemctl status myapp
ss -tlnp | grep :8000
curl http://localhost:8000/health

# 7. 配置 nginx 反向代理
sudo vim /etc/nginx/sites-available/myapp
sudo ln -s /etc/nginx/sites-available/myapp /etc/nginx/sites-enabled/
sudo nginx -t                # 测试配置
sudo systemctl reload nginx  # 平滑重载

# 8. 验证
curl -I http://your-domain.com

# 9. 出问题查日志
sudo journalctl -u myapp -n 100 --no-pager
sudo tail -f /var/log/nginx/error.log