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Linux系统服务

概述

Linux系统服务是在后台运行的程序，通过systemd或传统init系统管理。

systemd服务管理

基本操作

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# 查看服务状态
systemctl status nginx
systemctl status sshd

# 启动服务
systemctl start nginx

# 停止服务
systemctl stop nginx

# 重启服务
systemctl restart nginx

# 重载配置
systemctl reload nginx

# 查看是否激活
systemctl is-active nginx

# 查看是否开机自启
systemctl is-enabled nginx

开机自启

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# 启用开机自启
systemctl enable nginx

# 禁用开机自启
systemctl disable nginx

# 启用并立即启动
systemctl enable --now nginx

# 禁用并立即停止
systemctl disable --now nginx

服务列表

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

# 列出运行中的服务
systemctl list-units --type=service --state=running

# 列出失败的服务
systemctl list-units --type=service --state=failed

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

# 列出已启用的服务
systemctl list-unit-files --type=service --state=enabled

编写systemd服务

简单服务文件

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# /etc/systemd/system/myapp.service
[Unit]
Description=My Application
After=network.target

[Service]
Type=simple
User=myapp
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/bin/myapp
Restart=on-failure

[Install]
WantedBy=multi-user.target

服务类型

类型 说明
simple 主进程就是服务进程
forking 服务进程fork后退出
oneshot 执行一次后退出
notify 服务会发送通知
dbus D-Bus激活的服务

完整服务示例

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

[Service]
Type=notify
User=myapp
Group=myapp
WorkingDirectory=/opt/myapp

Environment="NODE_ENV=production"
EnvironmentFile=/opt/myapp/.env

ExecStart=/opt/myapp/bin/myapp --config /opt/myapp/config.yaml
ExecReload=/bin/kill -HUP $MAINPID
ExecStop=/bin/kill -WINCH $MAINPID

Restart=on-failure
RestartSec=5s

LimitNOFILE=65535
LimitNPROC=4096

PrivateTmp=true
ProtectSystem=strict
NoNewPrivileges=true

StandardOutput=journal
StandardError=journal
SyslogIdentifier=myapp

[Install]
WantedBy=multi-user.target

应用服务文件

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# 重载systemd配置
systemctl daemon-reload

# 启用并启动
systemctl enable --now myapp

# 查看状态
systemctl status myapp

# 查看日志
journalctl -u myapp

服务依赖

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[Unit]
Description=My Service
After=network.target        # 在network后启动
Requires=network.target     # 依赖network
Wants=network-online.target # 希望network在线
Conflicts=oldapp.service    # 与oldapp冲突
Before=otherapp.service     # 在otherapp之前启动

服务日志

journalctl查看

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# 查看服务日志
journalctl -u nginx

# 实时查看
journalctl -u nginx -f

# 限制行数
journalctl -u nginx -n 100

# 按时间过滤
journalctl -u nginx --since "1 hour ago"
journalctl -u nginx --since "2024-01-01"
journalctl -u nginx --since "2024-01-01 10:00:00" --until "2024-01-01 11:00:00"

# 按优先级过滤
journalctl -u nginx -p err
journalctl -u nginx -p warning

# 查看内核消息
journalctl -k

# 持续监控所有日志
journalctl -f

传统init脚本

/etc/init.d脚本

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#!/bin/bash
# /etc/init.d/myapp

case "$1" in
    start)
        echo "Starting myapp"
        /opt/myapp/bin/myapp &
        echo $! > /var/run/myapp.pid
        ;;
    stop)
        echo "Stopping myapp"
        kill $(cat /var/run/myapp.pid)
        rm /var/run/myapp.pid
        ;;
    restart)
        $0 stop
        $0 start
        ;;
    status)
        if [ -f /var/run/myapp.pid ]; then
            echo "myapp is running"
        else
            echo "myapp is not running"
        fi
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|status}"
        exit 1
        ;;
esac

exit 0
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# 使用service命令
service myapp start
service myapp stop
service myapp status

定时器服务

创建定时器

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# /etc/systemd/system/mytask.service
[Unit]
Description=My Task

[Service]
Type=oneshot
ExecStart=/opt/scripts/mytask.sh
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# /etc/systemd/system/mytask.timer
[Unit]
Description=My Task Timer

[Timer]
OnCalendar=*-*-* 02:00:00    # 每天凌晨2点
Persistent=true               # 错过时间后补执行

[Install]
WantedBy=timers.target
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# 启用定时器
systemctl enable --now mytask.timer

# 查看定时器
systemctl list-timers

定时器配置

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[Timer]
OnCalendar=*-*-* 02:00:00     # 每天2点
OnCalendar=*-*-* *:0:0        # 每小时
OnCalendar=Mon *-*-* 00:00:00 # 每周一
OnCalendar=*-*-01 00:00:00    # 每月1号

OnBootSec=5min                # 启动后5分钟
OnUnitActiveSec=1h            # 每小时执行

RandomizedDelaySec=300        # 随机延迟（分散负载）

Socket激活

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# /etc/systemd/system/myapp.socket
[Unit]
Description=My App Socket

[Socket]
ListenStream=8080

[Install]
WantedBy=sockets.target
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# /etc/systemd/system/myapp@.service
[Unit]
Description=My App Instance

[Service]
ExecStart=/opt/myapp/bin/myapp
StandardInput=socket

服务资源限制

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[Service]
# CPU限制
CPUQuota=50%
CPUShares=512

# 内存限制
MemoryLimit=1G
MemoryHigh=800M
MemoryLow=200M

# 进程数限制
LimitNPROC=100

# 文件描述符限制
LimitNOFILE=65535

# I/O限制
IOReadBandwidthMax=/dev/sda1 10M
IOWriteBandwidthMax=/dev/sda1 10M

参考资料