The shutdown command brings the system down in a secure way. All logged-in users are notified that the system is going down, and login operations are blocked. It is possible to shut the system down immediately, or after a specified delay.
All processes are first notified that the system is going down by the signalSIGTERM. This gives programs like vi time to save the file being edited, mail and news processing programs a chance to exit cleanly, etc.
shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to halt the system, runlevel 6 is used to reboot the system, and runlevel 1 is used to put the system into a state where administrative tasks can be performed (single-user mode). Runlevel 1 is the default, unless the -h or -r options are specified.
Your system may have a different set of options for the shutdown command; check your documentation for details.
Control access to the shutdown command using the control access file /etc/shutdown.allow. See Access Control below for more information.
-k
Do not shut down, but send the warning messages as if the shutdown were real.
-r
Reboot after shutdown.
-h
Instructs the system to shut down and then halt.
-P
Instructs the system to shut down and then power down.
-H
If -h is also specified, this option instructs the system to drop into boot monitor on systems that support it.
-f
Skip fsck after reboot.
-F
Force fsck after reboot.
-n
Don't call init to do the shutdown of processes; instruct shutdown to do that itself.
The use of this option is discouraged, and its results are not always predictable.
-c
Cancel a pending shutdown. (This does not apply to "shutdown now", which does not wait before shutting down.) With this option, it is not possible to give the time argument, but you can still specify an explanatory message that will be sent to all users.
-tsec
Tell init to wait sec seconds between sending processes the warning and the kill signal, before changing to another runlevel.
time
The time argument specifies when to perform the shutdown operation.
The time can be formatted in different ways:
First, it can be an absolute time in the format hh:mm, in which hh is the hour (1 or 2 digits, from 0 to 23) and mm is the minute of the hour (in two digits).
Second, it can be in the format +m, in which m is the number of minutes to wait.
Also, the word now is the same as specifying +0; it shuts the system down immediately.
message
A message to be sent to all users, along with the standard shutdown notification.
Details
If a shutdown is scheduled for the future, it will create the advisory file /etc/nologin which causes programs such as login not to allow new user logins. This file is created five minutes before the shutdown sequence starts. shutdown removes this file if it is stopped before it can signal init (i.e. it is cancelled or something goes wrong). It also removes it before calling init to change the runlevel.
The -f flag means "reboot fast". This only creates an advisory file /fastboot which can be tested by the system when it comes up again. The system boot rc file ("rc" stands for "runcom", which is short for "run commands") can test if this file is present, and decide not to run fsck since the system has been shut down in the proper way. After that, the boot process should remove /fastboot.
The -F flag means "force fsck". This only creates an advisory file /forcefsck which can be tested by the system when it comes up again. The boot rc file can test if this file is present, and decide to run fsck with a special "force" flag so that even properly unmounted file systems get checked. After that, the boot process should remove /forcefsck.
The -n flag causes shutdown not to call init, but to kill all running processes itself. shutdown will then turn off quota, accounting, and swapping and unmount all file systems.
Access Control
shutdown can be called from init when the Ctrl+Alt+Del key combination is pressed, if there exists an appropriate entry in /etc/inittab. This would mean that everyone who has physical access to the console keyboard can shut the system down, however.
To prevent this, shutdown can check to see if an authorized user is logged in. If shutdown is called with the -a argument (add this to the invocation of shutdown in /etc/inittab), it checks to see if the file /etc/shutdown.allow is present. It then compares the login names in that file with the list of people that are logged in on a virtual console (from /var/run/utmp). Only if one of those authorized users or root is logged in, it will proceed. Otherwise, it will write the message
shutdown: no authorized users logged in
...to the (physical) system console. The format of /etc/shutdown.allow is one username per line. Empty lines and comment lines (prefixed by a #) are allowed. Currently there is a limit of 32 users in this file.
Note that if /etc/shutdown.allow is not present, the -a argument is ignored.
Halting vs. Powering Off
The -H option just sets the initenvironment variableINIT_HALT to HALT, and the -P option just sets that variable to POWEROFF. The shutdown script that calls halt as the last thing in the shutdown sequence should check these environment variables and call halt with the right options for these options to actually have any effect.
shutdown +15 "Upgrading hardware, downtime should be minimal"
Schedule the system to shut down in fifteen minutes. Along with the normal message alerting users that the system is shutting down, they will be given the descriptive message about a hardware upgrade.
shutdown now
Bring down the system immediately.
shutdown -r now
Bring down the system immediately, and automatically reboot it.
shutdown -P now
Bring down the system immediately, and automatically power off the system.
shutdown (關閉或重新啟動該系統)
在類Unix操作系統，shutdown命令關閉或重新啟動該系統。
On Unix-like operating systems, the shutdown command shuts down or reboots the system.
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1 shutdown 運行系統環境
2 shutdown 描述
3 shutdown 語法
4 shutdown 例子
shutdown 運行系統環境
Unix&Linux
shutdown 描述
在shutdow命令使以安全的方式關閉系統。將通知所有已登錄用戶系統正在關閉，并且login操作被阻止。可以立即關閉系統，也可以在指定的延遲后關閉系統。
首先，通過信號 SIGTERM通知所有進程系統正在關閉。這使諸如vi的程序有時間保存正在編輯的文件，郵件和新聞處理程序有機會干凈退出等。
shutdown通過發信號通知init進程來完成其工作，要求其更改運行級別。運行級別0用于停止系統，運行級別6用于重新引導系統，運行級別1用于將系統置于可以執行管理任務的狀態（單用戶模式）。除非指定-h或-r選項，否則運行級別1是缺省值。
您的系統對于shutdown命令可能具有不同的選項集。查看您的文檔以了解詳細信息。
The shutdown command brings the system down in a secure way. All logged-in users are notified that the system is going down, and login operations are blocked. It is possible to shut the system down immediately, or after a specified delay.
All processes are first notified that the system is going down by the signal SIGTERM. This gives programs like vi time to save the file being edited, mail and news processing programs a chance to exit cleanly, etc.
shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to halt the system, runlevel 6 is used to reboot the system, and runlevel 1 is used to put the system into a state where administrative tasks can be performed (single-user mode). Runlevel 1 is the default, unless the -h or -r options are specified.
Your system may have a different set of options for the shutdown command; check your documentation for details.
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shutdown 語法
選件
不鼓勵使用此選項，并且其結果并非總是可預測的。
的時間可以不同的方式被格式化：
首先，它可以在格式的絕對時間HH ：毫米，其中HH表示小時（1或2位，從0至23）和毫米表示小時的分鐘（兩位數）。
其次，它可以采用+ m的格式，其中m是等待的分鐘數。
另外，單詞現在與指定+0相同；它會立即關閉系統。
細節
如果計劃在將來shutdown，它將創建咨詢文件/ etc / nologin，這將導致諸如login之類的程序不允許新用戶登錄。該文件是在關閉順序開始前五分鐘創建的。如果該文件在發出啟動信號之前已停止（即已取消或出現問題），則shutdown會刪除該文件。它還會在調用init更改運行級別之前將其刪除。
在-f標志的意思是“快速重啟”。這只會創建一個咨詢文件/ fastboot，當再次出現該文件時，系統可以對其進行測試。系統引導rc文件（“ rc”代表“ runcom”，是“ run命令”的縮寫）可以測試該文件是否存在，并決定不運行fsck，因為系統已通過正確的方式關閉了。之后，引導過程應刪除/ fastboot。
該-F標志的意思是“力量的fsck ”。這只會創建一個咨詢文件/ forcefsck，再次出現該文件時，系統可以對其進行測試。引導rc文件可以測試該文件是否存在，并決定使用特殊的“ force”標志運行fsck，以便甚至檢查正確卸載的文件系統。之后，引導過程應刪除/ forcefsck。
該-n標志導致shutdow不調用初始化，但殺死所有正在運行的進程本身。然后shutdown將關閉quota，accounting和交換并卸載所有文件系統。
訪問控制
如果在/ etc / inittab中存在適當的條目，則可以在按下Ctrl + Alt + Del組合鍵時從init調用shutdown。但是，這意味著可以物理訪問控制臺鍵盤的每個人都可以關閉系統。
為了防止這種情況，shutdow可以檢查，看看是否被授權的用戶登錄，如果shutdow時調用-a參數（這個增加的調用關閉在/ etc / inittab中），它會檢查該文件在/ etc /shutdown.allow存在。然后，它將該文件中的登錄名與在虛擬控制臺上登錄的人員列表進行比較（來自/ var / run / utmp）。僅當這些授權用戶或root用戶之一登錄時，它才會繼續。否則，它將寫消息
...到（物理）系統控制臺。/etc/shutdown.allow的格式是每行一個用戶名。允許使用空行和注釋行（以＃開頭）。目前，此文件中的用戶數限制為32。
請注意，如果不存在/etc/shutdown.allow，則-a參數將被忽略。
停止與關機
該-H選項僅設置init 環境變量 INIT_HALT到HALT，和-P選項只是設置該變量POWEROFF。在關閉序列中最后一個調用halt的關閉腳本應該檢查這些環境變量，并使用正確的選項調用halt，以使這些選項真正生效。
檔案
/ fastboot
/ etc / inittab
/etc/init.d/halt
/etc/init.d/reboot
/etc/shutdown.allow
Options
The use of this option is discouraged, and its results are not always predictable.
The time can be formatted in different ways:
First, it can be an absolute time in the format hh:mm, in which hh is the hour (1 or 2 digits, from 0 to 23) and mm is the minute of the hour (in two digits).
Second, it can be in the format +m, in which m is the number of minutes to wait.
Also, the word now is the same as specifying +0; it shuts the system down immediately.
Details
If a shutdown is scheduled for the future, it will create the advisory file /etc/nologin which causes programs such as login not to allow new user logins. This file is created five minutes before the shutdown sequence starts. shutdown removes this file if it is stopped before it can signal init (i.e. it is cancelled or something goes wrong). It also removes it before calling init to change the runlevel.
The -f flag means "reboot fast". This only creates an advisory file /fastboot which can be tested by the system when it comes up again. The system boot rc file ("rc" stands for "runcom", which is short for "run commands") can test if this file is present, and decide not to run fsck since the system has been shut down in the proper way. After that, the boot process should remove /fastboot.
The -F flag means "force fsck". This only creates an advisory file /forcefsck which can be tested by the system when it comes up again. The boot rc file can test if this file is present, and decide to run fsck with a special "force" flag so that even properly unmounted file systems get checked. After that, the boot process should remove /forcefsck.
The -n flag causes shutdown not to call init, but to kill all running processes itself. shutdown will then turn off quota, accounting, and swapping and unmount all file systems.
Access Control
shutdown can be called from init when the Ctrl+Alt+Del key combination is pressed, if there exists an appropriate entry in /etc/inittab. This would mean that everyone who has physical access to the console keyboard can shut the system down, however.
To prevent this, shutdown can check to see if an authorized user is logged in. If shutdown is called with the -a argument (add this to the invocation of shutdown in /etc/inittab), it checks to see if the file /etc/shutdown.allow is present. It then compares the login names in that file with the list of people that are logged in on a virtual console (from /var/run/utmp). Only if one of those authorized users or root is logged in, it will proceed. Otherwise, it will write the message
...to the (physical) system console. The format of /etc/shutdown.allow is one username per line. Empty lines and comment lines (prefixed by a #) are allowed. Currently there is a limit of 32 users in this file.
Note that if /etc/shutdown.allow is not present, the -a argument is ignored.
Halting vs. Powering Off
The -H option just sets the init environment variable INIT_HALT to HALT, and the -P option just sets that variable to POWEROFF. The shutdown script that calls halt as the last thing in the shutdown sequence should check these environment variables and call halt with the right options for these options to actually have any effect.
Files
/fastboot
/etc/inittab
/etc/init.d/halt
/etc/init.d/reboot
/etc/shutdown.allow
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shutdown 例子
安排系統在上午8點關閉
安排系統在晚上8點關閉
安排系統在15分鐘內關閉。除了警告用戶系統已關閉的正常消息外，還將為他們提供有關硬件升級的描述性消息。
立即關閉系統。
立即關閉系統，然后自動重新引導它。
立即關閉系統，并自動關閉系統電源。
Schedule the system to shut down at 8 A.M.
Schedule the system to shut down at 8 P.M.
Schedule the system to shut down in fifteen minutes. Along with the normal message alerting users that the system is shutting down, they will be given the descriptive message about a hardware upgrade.
Bring down the system immediately.
Bring down the system immediately, and automatically reboot it.
Bring down the system immediately, and automatically power off the system.
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其他命令行
sysklogd | s2p | service | sag | set | setenv | setfacl | sfdisk | sha224sum | sha256sum | sha384sum | sha512sum | sleep | stat | startx | strftime | strip | swapoff | shred |