Linux Five restart commands and specific instructions

First,Linux five restart command

1, shutdown

2, Poweroff

3. Init

4, reboot

5, halt

Ii. Specific instructions for five restart commands

Shutdown

Reboot

Under Linux Some common shutdown/restart commands have shutdown, halt, reboot, and INIT, they can reach the intention of rebooting the system, but each instruction internal operation process is not the same, after the introduction of this article, I hope you can more sensitive use of various shutdown instructions.

1.shutdown

Shutdown command to safely shut down the system. It is dangerous for some users to turn Linux off using a direct power-off. Because Linux, unlike Windows, runs many processes in the background, forcing a shutdown can cause data loss to the process, leave the system in an unstable state, or even damage the hardware device in some systems. With the shutdown command before the system shuts down, the system administrator notifies all logged-on users that the system will be closed. And the login command is frozen, that is, the new user can no longer log in. It is possible to shut down directly or delay a certain amount of time before shutting down, and it may be possible to restart the computer. This is the signal that the system will receive from all Processes (process) (signal)

Decision-making. This allows programs like VI to have time to store documents that are currently being edited, while programs like Mail (mail) and news (news) can leave normally and so on.

Shutdown performs its job of sending a signal (signal) to the INIT program, requiring it to change the runlevel.

Runlevel 0 is used to stop (halt),runlevel 6 is used to reactivate the (reboot) system, and Runlevel 1 is used to get the system into the state of the management work can be done, this is a preset, assuming that there is no-H and no-R parameter to shutdown. To find out what you did during the (halt) or reboot (reboot), you can see these runlevels related information in this file/etc/inittab.

Shutdown parameter Description:

[-T] tell Init how long it will shut down before changing to another runlevel.

[-R] Restart calculator.

[-K] does not really shut down, just send a warning signal to

(login) per log-in person.

[-h] turn off the power (halt) after shutting down the machine.

[-n] do not use init, but to shut down the machine. The use of this option is discouraged, and the consequences of this option are often not always what you expect it to be.

[-c] Cancel current process cancels the shutdown program that is currently executing. So this option certainly does not have a time parameter, but you can enter a message to interpret, and this information will be sent to each user.

[-f] ignores fsck when restarting the calculator (reboot).

[-f] forces fsck to restart the calculator (reboot).

[-time] Sets the time before the shutdown (shutdown).

2.halt----The simplest shutdown command

In fact, halt is called shutdown-h. When the halt executes, the application process is killed, the sync system is called, and the kernel is stopped after the file system write operation is complete.

Parameter description:

[-n] prevents the sync system from being called, it is used after patching the root partition with fsck to prevent the kernel from overwriting the patched super block with the old version of the Super Block (superblock).

[-W] is not a real reboot or shutdown, just write

Wtmp(/var/log/wtmp) record.

[-d] does not write wtmp record (included in option [-n]).

[-f] does not invoke shutdown and forces shutdown or restart.

[-i] before shutting down (or restarting), turn off all network interfaces.

[-p] This option is the default option. is to call Poweroff when shutting down the machine.

3.reboot

Reboot works almost like halt, but it triggers a host reboot, and Halt is shut down. Its parameters are not much different from the halt.

4.init

Init is the ancestor of all processes, its process number has been 1, so send a term signal to INIT will stop all the user process ﹑ daemon and so on. Shutdown is the use of this mechanism. Init defines 8 operating levels (runlevel), Init 0 for shutdown,init 1 for restart. For Init to be lengthy, it is no longer narrated here. There are other telinit instructions that can change the operation level of INIT, such as,telinit-is can make the system into a single user form, and not get information and wait time when using shutdown.

The above is the Linux five restart instructions specific application instructions, thank you for reading.

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Linux Five restart commands and specific instructions