作用:Force changed blocks to disk, update the super block. 促使内存块中数据存进磁盘,更新超级块。
2.shutdown - Halt, power-off or reboot the machine 这三个命令用来停止,断电或重启机器。语法:shutdown [OPTIONS…] [TIME] [WALL…]
time :now 立刻 ,HH:mm 定时关机,+m m分钟后关机
例如:shutdown -P now 立即关机
用法:
语法:halt [OPTIONS…] reboot [OPTIONS…]–halt Halt the machine, regardless of which one of the three commands is invoked.不论三个命令中的哪个命令被调用,停止机器运行,但不断电。(可能是中止之前的命令执行)-p, --poweroff Power-off the machine, regardless of which one of the three commands is invoked.不论三个命令中的哪个命令被调用,都关机–reboot Reboot the machine, regardless of which one of the three commands is invoked.不论三个命令中的哪个命令被调用,都重启。-f, --force Force immediate halt, power-off, reboot. Do not contact the init system.立即执行相应命令,不和系统交互。