CentOS 7下的 systemd
安装下centos 7 ，发现已不能在/etc/init.d/配置服务了，网上学学一下。CentOS 7使用systemd替换了现在常用的System V与BSD风格init程序。
systemd采用了以下新技术：
- 采用Socket激活式与总线激活式服务，以提高相互依赖的各服务的并行运行性能；
- 用cgroups代替PID来追踪进程，以此即使是两次fork之后生成的守护进程也不会脱离systemd的控制。
systemd服务管理
systemctl is-enabled .service #查询服务是否开机启动 systemctl enable .service #开机运行服务 systemctl disable .service #取消开机运行 systemctl start .service #启动服务 systemctl stop .service #停止服务 systemctl restart .service #重启服务 systemctl reload .service #重新加载服务配置文件 systemctl status .service #查询服务运行状态 systemctl --failed #显示启动失败的服务
[root@lab ~]# systemctl status httpd.service
httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled)
Active: active (running) since Sat 2014-07-12 15:30:07 CST; 5 days ago
Process: 3229 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
Process: 3868 ExecReload=/usr/sbin/httpd $OPTIONS -k graceful (code=exited, status=0/SUCCESS)
Main PID: 3234 (httpd)
Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
CGroup: /system.slice/httpd.service
+-3234 /usr/sbin/httpd -DFOREGROUND
+-3874 /usr/sbin/httpd -DFOREGROUND
+-3875 /usr/sbin/httpd -DFOREGROUND
+-3876 /usr/sbin/httpd -DFOREGROUND
+-3877 /usr/sbin/httpd -DFOREGROUND
+-3878 /usr/sbin/httpd -DFOREGROUND
+-8338 /usr/sbin/httpd -DFOREGROUND
+-8339 /usr/sbin/httpd -DFOREGROUND
+-8340 /usr/sbin/httpd -DFOREGROUND
Jul 12 15:30:07 localhost.localdomain httpd[3234]: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using lo... message
Jul 12 15:30:07 localhost.localdomain systemd[1]: Started The Apache HTTP Server.
Jul 13 03:40:01 lab.qzlab.cn systemd[1]: Reloading The Apache HTTP Server.
Jul 13 03:40:02 lab.qzlab.cn httpd[3868]: AH00557: httpd: apr_sockaddr_info_get() failed for lab.qzlab.cn
Jul 13 03:40:02 lab.qzlab.cn httpd[3868]: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0....s message
Jul 13 03:40:02 lab.qzlab.cn systemd[1]: Reloaded The Apache HTTP Server.
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