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From time to time, you will need to shut the system down. This is necessary for scheduled maintenance, running diagnostics, hardware changes or additions, and other administrative tasks. During a clean system shutdown, the following actions take place: All users are notified that the system will be going down, preferably giving them some reasonable advance warning. All running processes are sent a signal telling them to terminate, allowing them time to exit gracefully, provided the program has made provisions to do so. All subsystems are shut down gracefully, via the commands they provide for doing so. All remaining users are logged off, and remaining processes are killed. Filesystem integrity is maintained by completing all pending disk updates. Depending on the type of shutdown, the system moves to single-user mode, the processor is halted, or the system is rebooted. After taking these steps, the administrator can turn the power off, execute diagnostics, or perform other maintenance activities as appropriate.
Multiple sync commands raise the probability that the write will take place before you enter another command (or turn off the power) by taking up the time needed to complete the operation. However, the same effect can be obtained by waiting a few seconds for disk activity to cease before doing anything else. Typing "sync" several times gives you something to do while you're waiting. There is one situation in which you do not want sync to be executed, either manually or automatically: when you have run fsck manually on the root filesystem. If you sync the disks at this point, you will rewrite the bad superblocks stored in the kernel buffers and undo the fixing fsck just did. In such cases, on BSD-based systems and under HP-UX, you must use the -n option to reboot or shutdown to suppress the usual automatic sync operation. FreeBSD and System V are smarter about this issue. The fsck command generally will automatically remount the root filesystem when it has modified the root filesystem. Thus, no special actions are required to avoid syncing the disks.
The reboot command performs the same function. shutdown -h says to halt the processor instead of shutting down to single-user mode. Once this process completes, the power may be safely turned off. You can also use the halt command to explicitly halt the processor once single-user mode is reached. shutdown -k inaugurates a fake system shutdown: the shutdown messages are sent out normally, but no shutdown actually occurs. I suppose the theory is that you can scare users off the system this way, but some users can be pretty persistent, preferring to be killed by shutdown rather than log out. The Linux shutdown Command The version of shutdown found on most Linux systems also has a -t option which may be used to specify the delay period between when the kernel sends the TERM signal to all remaining processes on the system and when it sends the KILL signal. The default is 30 seconds. The following command shuts down the system more rapidly, allowing only 5 seconds between the two signals: # shutdown -h -t 5 now The command version also provides a -a option, which provides a limited security mechanism for the shutdown command.
On most systems, the only way to abort a pending system shutdown is to kill the shutdown process. Determine the shutdown process' process ID by using a command like the following: # ps -ax | grep shutdown BSD-style # ps -ef | grep shutdown System V-style Then use the kill command to terminate it: # ps -ef | grep shutdown 25723 co S 0:01 /etc/shutdown -g300 -i6 -y 25800 co S 0:00 grep shutdown # kill -9 25723 It's only safe to kill a shutdown command during its grace period; once it has actually started closing down the system, you're better off letting it finish and then rebooting. The Linux version of shutdown includes a -c option that cancels a pending system shutdown. Every version should be so helpful.
I have been... (2 Replies) Discussion started by: Judo_Bear 7. AIX Hi, is there a difference between shutdown -Fand shutdown -h now? (3 Replies) Discussion started by: x_adm 3 Replies 8. UNIX for Advanced & Expert Users Dear all, I've just installed a Vanilla kernel (last stable version downloaded from) as an exercice in order to better understand how to compile linux kernel. I loaded the file of the current kernel (Redhat kernel) in the menuconfig in order to restore all already... (0 Replies) Discussion started by: dariyoosh 0 Replies 9. AIX After issuing shutdown -F or shutdown -F now my server is getting restarted. Any Idea? (3 Replies) Discussion started by: laris 10. Solaris Hi is shutdown and init 0 are same command in solaris? (2 Replies) Discussion started by: mokkan 2 Replies
If possible, automatically turns off power on systems that support this feature. init 6 To shut down the system to run level 0, and then reboot to multiuser level with NFS resources shared (or anyother level is the default in the inittab file). ================================= How to find out, in which LEVEL my system is running? $ who -r /etc/inittab file init is a daemon (daemon is a background program). when init command is run, init daemon reads the contents in /etc/inittab file. In this file, follwing thing are there: The system's default run level What processes to start, monitor, and restart if they terminate What actions to take when the system enters a new run level ================================================ Complete details on init command is available at
Shut Down or Reboot a Solaris System Normally, the system reboots at power-up or after a system crash. You can reboot a system by using either the init command or the reboot command. The init 6 command asks for stop methods (either SMF or rc. d). Whereas, the reboot command does not, thereby making the reboot command a more reliable way of rebooting a system. Solaris is usually used as a server operating system. Because of this, you want to make sure that you shut the system down as gracefully as possible to ensure there isn't any data loss. For every application that is installed on your server, you should make sure that you have the correct scripts in /etc/rc(x). d to gracefully shut down the service. Shutdown You have more than one command option that you can use. The best command is this, executed as root: shutdown -y -i5 -g0 This will immediately shut the system down. You can also use the older command that still works: sync;sync;init 5 You can even use: poweroff Reboot If you are trying to reboot the system as opposed to turning it off, you could use: shutdown -y -i6 -g0 Or: sync;sync;init 6 Or even: reboot So many commands to do the same thing…
The shutdown command for solaris is root# init 0 you should get "ok" as output In the "ok" prompt, type " poweroff " ================================================== init 0 is called as PROM mode. It is used to bring a running system to the OK prompt, either to turn the system off or to perform a PROM ok prompt is also called as OPEN BOOT PROMPT mode function =============================================== The important Levels are: init 0 To shut down the operating system; then you can turn off the pwoer safely init s or S To run as a single user with some file systems mounted and accessible. init 1 To access all available file systems. User logins are disabled init 2 For normal operations. Multiple users can access the system and all file system. All daemons are running except for the NFS server daemons init 3 (this is the default run level for solaris): For normal operations with NFS resources shared. This is the default run level for the Solaris OS. init 4 Not configured by default, but available for customer use init 5 To shut down the operating system so that it is safe to turn off power to the system.
When it is invoked with this option, the command determines whether any of the users listed in the file /etc/ are currently logged in on the console (or any virtual console attached to it). If not, the shutdown command fails. The purpose of this option is to prevent casual passers-by from typing Ctrl-Alt-Delete on the console and causing an (unwanted) system reboot. Accordingly, it is most often used in the inittab entry corresponding to this event. Ensuring Disk Accuracy with the sync Command As we've noted previously, one of the important parts of the shutdown process is syncing the disks. The sync command finishes all disk transactions and writes out all data to disk, guaranteeing that the system can be turned off without corrupting the files. You can execute this command manually if necessary: # sync # sync Why is sync executed two or three times (or even more [ 15])? I think this is a bit of Unix superstition. The sync command schedules but does not necessarily immediately perform the required disk writes, even though the Unix prompt returns immediately.
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