Solaris System Shutdown

The first three commands—/usr/sbin/shutdown, /sbin/init, and /usr/sbin/halt—initiate shutdown procedures, kill all running processes, write data to disk, and shut down the system software to the appropriate run level. The /usr/sbin/reboot  command does all these tasks as well, and it then boots the system back to the state defined as initdefault  in /etc/inittab. The /usr/sbin/poweroff  command is equivalent to init  state 5. The last command, which is really a series of keystrokes, stops the system unconditionally.

CAUTION

Aborting the Operating System Using the Stop+A key sequence (or L1+A) abruptly breaks execution of the operating system and should be used only as a last resort to restart the system.

The /usr/sbin/shutdown  Command

You use the shutdown  command to shut down a system that has multiple users. The shutdown  command sends a warning message to all users who are logged in, waits for 60 seconds (by default), and then shuts down the system to single-user state. The command option -g  lets you choose a different default wait time. The -i  option lets you define the init  state to which the system will be shut down. The default is S.

NOTE

Sending a Shutdown Message When using either shutdown  or init, you might want to give users advance notice by sending an email message about any scheduled system shutdown.

The shutdown  command performs a clean system shutdown, which means that all system processes and services are terminated normally, and file systems are synchronized. You need superuser privileges to use the shutdown  command.

When the shutdown  command is initiated, all logged-in users and all systems mounting resources receive a warning about the impending shutdown, and then they get a final message. For this reason, the shutdown  command is recommended over the init  command on a server with multiple users.

The proper sequence of shutting down the system is described in Step by Step 3.3

Step by Step 3.3: Shutting Down a System

1. As superuser, type the following to find out if users are logged in to the system:

   # who

2. A list of all logged-in users is displayed. You might want to send an email message or broadcast a message to let users know that the system is being shut down.
3. Shut down the system by using the shutdown  command:

   # shutdown -i<init-state> -g<grace-period> -y

Options for the shutdown  Command

The /sbin/init  Command

You use the init  command to shut down a single-user system or to change its run level. The syntax is as follows:

init <run-level>

<run-level>  is any run level described in Table 3.21. In addition, <run-level>  can be a, b, or c, which tells the system to process only /etc/inittab  entries that have the a, b, or c  run level set. These are pseudo-states, which can be defined to run certain commands but which do not cause the current run level to change. <run-level>  can also be the keyword Q  or q, which tells the system to reexamine the /etc/inittab  file.

You can use init  to place the system in power-down state (init  state 0) or in single-user state (init  state 1). For example, to bring the system down to run level 1  from the current run level, you type the following:

init 1

NOTE

The telinit  Command The telinit  command is the same as the init  command. It is simply a link to the /usr/sbin/init  command.

The system responds with this:

INIT: New run level: 1
Changing to state 1.
Unmounting remote filesystems: /vol nfs done.
System services are now being stopped.
Mar 14 13:13:22 unknown /usr/sbin/vold[475]: problem unmounting /vol;
Interrupted system call
Mar 14 13:13:22 unknown pseudo: pseudo-device: tod0
Mar 14 13:13:22 unknown genunix: tod0 is /pseudo/tod@0
Mar 14 13:13:22 unknown pseudo: pseudo-device: pm0
Mar 14 13:13:22 unknown genunix: pm0 is /pseudo/pm@0
Print services stopped.
Mar 14 13:13:22 unknown syslogd: going down on signal 15
Killing user processes: done.
Change to state 1 has been completed.
Type control-d to proceed with normal startup,
(or give root password for system maintenance):

As another example, say you made a change to the /etc/inittab  file and you want to have the system reread /etc/inittab  and implement the change. In this case, you type the following:

init q

No system messages are displayed, and the inittab  file is reexamined.

The /usr/sbin/halt  Command

You use the halt  command when the system must be stopped immediately and it is acceptable not to warn current users. The halt  command shuts down the system without delay and does not warn other users on the system of the shutdown.

The /usr/sbin/reboot  Command

You use the reboot  command to shut down a single-user system and bring it into multiuser state. reboot  does not warn other users on the system of the shutdown.

The Solaris reboot  and halt  commands perform unconditional shutdown of system processes. These commands shut down the system much more quickly than the shutdown  command, but they do not do so as gracefully because they do not run the kill scripts located in /etc/rc<n>.d. No messages are sent to users; although reboot  and halt  do not notify all logged-in users and systems mounting resources of the impending shutdown, they do synchronize file systems.

The speed of such a reboot is useful in certain circumstances, such as when you're rebooting from the single-user run state. Also, the capability to pass arguments to OpenBoot via the reboot  command is useful. For example, this command reboots the system into run level s  and reconfigures the device tables:

reboot -- -rs

The /usr/sbin/poweroff  Command

The poweroff  command is equivalent to the init 5  command. The poweroff  command immediately shuts down the system, without running rc0  kill scripts. Users are not notified of the shutdown. If the hardware supports it, the poweroff  command also turns off power.

NOTE

The init  and shutdown  Commands Using init  and using shutdown  are the most reliable ways to shut down a system because these commands use rc  scripts to kill running processes and shut down the system with minimal data loss.

The halt, poweroff, and reboot  commands do not run the rc  scripts properly and are not the preferred method of shutting down the system.

Stopping the System for Recovery Purposes

Occasionally, a system might not respond to the init  commands described earlier in this chapter. A system that doesn't respond to anything, including reboot  or halt, is called a "crashed" or "hung" system. If you try to use the commands discussed in the preceding sections but get no response, you can press Stop+A or L1+A to get back to the boot PROM. (The specific Stop key sequence depends on your keyboard type.) On terminals connected to the serial port, you can press the Break key, as described in the section "Accessing the OpenBoot Environment," earlier in this chapter.

Some OpenBoot systems provide the capability of commanding OpenBoot by means of pressing a combination of keys on the system's keyboard, referred to as a keyboard chord or key combination. These keyboard chords are described in Table 3.26. When issuing any of these commands, you press the keys immediately after turning on the power to your system, and you hold down the keys for a few seconds until the keyboard light-emitting diodes (LEDs) flash.

Keyboard Chords

To change the default abort sequence on the keyboard, you need to edit the /etc/default/kbd  file. In that file, you can enable and disable keyboard abort sequences, and change the keyboard abort sequence. After modifying this file, you issue the kbd –i  command to update the keyboard defaults.

NOTE

Disabling Keyboard Chords The commands in Table 3.26 are disabled if PROM security is on. Also, if your system has full security enabled, you cannot apply any of these commands unless you have the password to get to the ok  prompt.

The process of breaking out of a hung system is described in Step by Step 3.4.

TIP

Interrupting a Hung System Step by Step 3.4 describes an objective that is sure to be on the exam. Make sure that you understand each step and the order in which the steps are executed.

Step by Step 3.4: Breaking Out of a Hung System

1. Use the abort key sequence for your system (Stop+A or L1+A).

   The monitor displays the ok  PROM prompt.

2. Type the sync  command to synchronize the disks:

   ok sync

   The sync procedure synchronizes the file systems and is necessary to prevent corruption to the file system.

3. When you see the syncing file systems  message, press the abort key sequence for your system again.
4. Type the appropriate reset  command to reset the hardware and start the boot process:

   ok reset

5. After you receive the login:  message, log in and type the following to verify that the system is booted to the specified run level:

   # who –r

6. The system responds with the following:

   run-level 3 Jun 9 09:19 3  0 S