systemd

Systemd 服务管理

概述

Systemd 服务单元编写、依赖管理、日志查看等技能。

服务管理

基础命令

# 启停服务
systemctl start service-name
systemctl stop service-name
systemctl restart service-name
systemctl reload service-name       # 重载配置（不中断服务）

# 开机启动
systemctl enable service-name
systemctl disable service-name
systemctl enable --now service-name # 启用并立即启动

# 查看状态
systemctl status service-name
systemctl is-active service-name
systemctl is-enabled service-name
systemctl is-failed service-name

服务列表

# 列出所有服务
systemctl list-units --type=service
systemctl list-units --type=service --state=running
systemctl list-units --type=service --state=failed

# 列出所有单元文件
systemctl list-unit-files --type=service

# 查看依赖
systemctl list-dependencies service-name
systemctl list-dependencies --reverse service-name

单元文件

文件位置

# 系统单元（包管理器安装）
/usr/lib/systemd/system/

# 管理员自定义
/etc/systemd/system/

# 运行时生成
/run/systemd/system/

# 优先级：/etc > /run > /usr/lib

基础服务单元

# /etc/systemd/system/myapp.service
[Unit]
Description=My Application
Documentation=https://example.com/docs
After=network.target
Wants=network-online.target

[Service]
Type=simple
User=appuser
Group=appgroup
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/bin/start.sh
ExecStop=/opt/myapp/bin/stop.sh
ExecReload=/bin/kill -HUP $MAINPID
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

服务类型

# simple（默认）- 主进程即服务进程
Type=simple
ExecStart=/usr/bin/myapp

# forking - 传统守护进程
Type=forking
PIDFile=/var/run/myapp.pid
ExecStart=/usr/bin/myapp -d

# oneshot - 一次性任务
Type=oneshot
ExecStart=/usr/bin/backup.sh
RemainAfterExit=yes

# notify - 服务就绪通知
Type=notify
ExecStart=/usr/bin/myapp

环境变量

[Service]
# 直接设置
Environment="VAR1=value1" "VAR2=value2"

# 从文件加载
EnvironmentFile=/etc/myapp/env
EnvironmentFile=-/etc/myapp/env.local  # - 表示可选

# 传递给子进程
PassEnvironment=HOME USER

资源限制

[Service]
# 文件描述符
LimitNOFILE=65535

# 进程数
LimitNPROC=4096

# 内存限制
MemoryLimit=512M
MemoryMax=1G

# CPU 限制
CPUQuota=50%

# 超时设置
TimeoutStartSec=30
TimeoutStopSec=30