What are the several restart commands in linux?

Five restart commands for Linux: 1. Shutdown command, which can be used to shut down the computer or restart it. The syntax is "shutdown -r now"; 2. Reboot command, which can be used to shut down the computer. Causes the host to restart; 3. init command, which can be restarted through "init 1"; 4. halt command, which can be used to restart or shut down; 5. poweroff command, which can be used to shut down the calculator and cut off the power supply.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

In the Linux system, commands are a very important part, because we can perform most operations through commands, making our work more efficient and convenient. So what are the reboot commands in Linux? There are five reboot commands in Linux, namely: shutdown, poweroff, init, reboot, and halt. The following is a detailed introduction.

halt	Shutdown	root user	halt: only shut down the system, the power supply is still running halt -p: Shut down the system and turn off the power (execute halt first, then poweroff)
poweroff	Shutdown	root user	poweroff will send a power-off signal to acpi
reboot	Restart	root user
shutdown	-h: Shutdown -r: Restart -c: Cancel shutdown operation	root user	shutdown actually calls init 0, init 0 will cleanup some work and then call halt or poweroff shutdown -r now: restart after one minute shutdown -r 05:30: restart at the latest 5:30 shutdown -r 10: Restart after ten minutes
init	init 0: Shutdown init 6: Restart	root user	init: Switch the running level of the system

Before shutting down or restarting, execute sync 3 to 4 times to update the data in the memory that has not been saved to the hard disk to the hard disk, otherwise data will be lost. When executing sync, run it as an administrator, because the administrator has permissions on all files, while ordinary users only have permissions on some of their own files.

1. Shutdown command

The shutdown command is the most commonly used and safest shutdown and restart command. It will call fsck to check the disk before shutting down, where -h and -r is the most commonly used parameter:

●-h: Stop the system service and shut down

●-r: Stop the system service and then restart

Example:

shutdown -h now  --立即关机  
shutdown -h 10:53  --到10:53关机，如果该时间小于当前时间，则到隔天  
shutdown -h +10  --10分钟后自动关机  
shutdown -r now  --立即重启  
shutdown -r +30 'The System Will Reboot in 30 Mins'   --30分钟后重启并并发送通知给其它在线用户

2. Reboot command

reboot means to restart immediately, and the effect is equivalent to shutdown -r now.

The working process of reboot is almost the same as halt, but it causes the host to restart, while halt is to shut down. Its parameters are similar to halt.

3. init command

init is the ancestor of all processes. Its process number is always 1, so sending the TERM signal to init will terminate all user processes. daemon process etc. shutdown uses this mechanism.

init defines 7 runlevels:

• init 0 means shutdown or shutdown (never set initdefault to 0 ),

• init 1 is single-user mode, and only the root user performs maintenance.

• init 2 - Multi-user, no NFS, no network

• init 3 - Complete Multi-user mode (standard run level)

• ##init 4 - not used

• init 5 - X11 (xwindow) graphical interface mode

• init 6 - Restart (do not set initdefault to 6)

4. Halt command

The halt command is the simplest shutdown command, which is actually calling

shutdown -h. When halt is executed, it ignores the current system status and performs a hardware shutdown; kills the application process, executes the sync system call, and stops the kernel after the file system write operation is completed.

When halt is executed, the application process is killed, the sync system call is executed, and the kernel is stopped after the file system write operation is completed.

Parameter description:

• [-n] Prevent sync system calls. It is used after patching the root partition with fsck to prevent the kernel from using old versions. The superblock superblock overwrites the patched superblock.

• [-w] Not really a reboot or shutdown, just writing.

• [-d] Do not write wtmp records.

  
  

• [-f] Force shutdown or restart without calling shutdown.

  
  

• [-i] Before shutting down or restarting, turn off all network interfaces.

  
  

• [-p] This option is the default option, which is to call poweroff when shutting down.

5. Poweroff command

poweroff means immediate shutdown, the effect is equivalent to

shutdown -h now, in multi-user Mode (Run Level 3) is not recommended.

The poweroff command is used to turn off the calculator and cut off the power supply.

Usage permissions: System administrator.

Syntax:

poweroff [-n] [-w] [-d] [-f] [-i] [-h]

Parameter description:

• -n Do not write memory data back to the hard disk before shutting down

  
  

• -w does not actually shut down, it just writes the records to the /var/log/wtmp file

  
  

• -d Do not write records to the /var/log/wtmp file

  
  

• -i Stop all network-related devices before shutting down

  
  

• -p Set all hardware in the system to standby mode before shutting down the operating system

  
  

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