systemctl -- 系统服务管理器

Posted 2020-10-30 the_tops ----

systemctl  -- 系统服务管理器

systemctl 是系统服务管理器命令，它实际上将 service 和 chkconfig 这两个命令组合到一起。

直接运行命令可以列出所有正在运行的服务，输出列表具有更详细的信息，比如：

[root@beyes   command]# systemctl
... ...
sendmail.service          loaded active exited        LSB: start and stop sendmail
sshd.service              loaded active running       LSB: Start up the OpenSSH server daemon
udev.service              loaded active running       udev Kernel Device Manager
... ...

这里，还有一个 systemd-cgls 命令可以以树状的形式列出正在运行的进程信息。

如果要启动 httpd 服务，那么运行下面命令：

[root@beyes   command]# systemctl start httpd.service

注意，上面的 httpd 后面的 .service 是不能少的。

同理，停止服务和重启服务可以分别如下运行命令：

# systemctl stop httpd.service       #停止服务
# systemctl restart httpd.service              #重启服务

如果我们要查看服务的运行状态，那么如下运行：

[root@beyes   command]# systemctl status httpd.service
httpd.service - LSB: start and stop Apache HTTP Server
      Loaded: loaded (/etc/rc.d/init.d/httpd)
      Active: active (running) since Wed, 22 Feb 2012 10:37:30 +0800; 2s ago
     Process: 2573 ExecStop=/etc/rc.d/init.d/httpd stop (code=exited, status=0/SUCCESS)
     Process: 2589 ExecStart=/etc/rc.d/init.d/httpd start (code=exited, status=0/SUCCESS)
    Main PID: 2594 (httpd)
      CGroup: name=systemd:/system/httpd.service
          ├ 2594 /usr/sbin/httpd
          ├ 2596 /usr/sbin/httpd
          ├ 2597 /usr/sbin/httpd
          ├ 2598 /usr/sbin/httpd
          ├ 2599 /usr/sbin/httpd
          ├ 2600 /usr/sbin/httpd
          ├ 2601 /usr/sbin/httpd
          ├ 2602 /usr/sbin/httpd
          └ 2603 /usr/sbin/httpd

如果我们打算让服务可以随机启动，那么如下运行：

[root@beyes   command]# systemctl enable httpd.service
httpd.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig httpd on

用 chkconfig 命令检测一下服务是否运行成功

[root@beyes   command]# chkconfig --list |grep httpd

Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.

httpd              0:off    1:off    2:on    3:on    4:on    5:on    6:off

可见服务已经在 第2 到 第5 运行等级打开。

同理禁止服务随机启动可以如下运行：

[root@beyes   command]# systemctl disable httpd.service
httpd.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig httpd off

用 chkconfig 检测一下：

[root@beyes   command]# chkconfig --list |grep httpd

Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.

httpd              0:off    1:off    2:off    3:off    4:off    5:off    6:off

已经关闭成功。

此外，我们还可以直接检测服务是否随机启动或否，如下运行命令：

[root@beyes   command]# systemctl is-enabled httpd.service; echo $?
httpd.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig httpd --level=5
0

上面，0 表示该服务已经使能随机启动；如果返回 1 那么表示该服务不随机启动

ref:http://www.groad.net/bbs/simple/?t6224.html