Chapter 8 Introduction to Shutting Down and Booting a System

The Solaris Operating System (Solaris OS) is designed to run continuously so that electronic mail and network resources are available to users. This chapter provides guidelines for shutting down and booting a system.

This is a list of the information in this chapter:

• What's New in Shutting Down and Booting a System

• Where to Find Shut Down and Boot Tasks

• Shut Down and Boot Terminology

• Guidelines for Shutting Down a System

• Guidelines for Booting a System

• When to Shut Down a System

• When to Boot a System

For an overview of all of the boot features and methods that are available in the Solaris release, see Chapter 9, Shutting Down and Booting a System (Overview)

For instructions on booting a Solaris system, see Chapter 12, Booting a Solaris System (Tasks).

What's New in Shutting Down and Booting a System

This section describes new boot features in the Solaris release.

x86: iSCSI Boot

Solaris Express Community Edition, build 104: The iSCSI Boot feature enables you to initialize an operating system over the network from a remote location, such as a storage disk array. This version of iSCSI Boot supports booting from x86 based systems. iSCSI Boot is typically loaded onto an initiator or a diskless client, while the hard disk resides on a SCSI target that is attached to the network. Because the feature uses a standard Ethernet-based infrastructure, data, storage, and networking traffic can be consolidated on a standard network. More information about iSCSI Boot can be found at http://wikis.sun.com/display/OpenSolarisInfo/iSCSI+Boot.

Fast Reboot on the x86 Platform

Solaris Express Community Edition, build 100, and the OpenSolaris 2008.11 release: The Fast Reboot feature enables you to reboot an x86 based system, bypassing the firmware and boot loader processes. Fast Reboot implements an in-kernel boot loader that loads the kernel into memory and then switches to that kernel, so that the reboot process occurs within seconds. This feature is implemented on both 32-bit and 64-bit kernels.

For more information about this feature, see x86: Introducing Fast Reboot.

ZFS Boot Support

Solaris Express Community Edition, builds 88 and 90: This release includes ZFS ^TM installation and boot support. Systems can now be installed and booted from a ZFS root file system. This implementation applies to both SPARC and x86 based systems. Booting, system operations, and installation procedures have been modified to support this change.

For more information, see Booting From a ZFS Root File System.

x86: New findroot Command

Solaris Express Community Edition, build 88: All Solaris installation methods, including Solaris Live Upgrade, now use the findroot command for specifying which disk slice on an x86 based system to boot. This implementation supports booting systems with ZFS roots, as well as UFS roots. Previously, the root command, root (hd0.0.a), was used to explicitly specify which disk slice to boot. This information is located in the menu.lst file that is used by GRUB.

The most common form of the GRUB menu.lst entry is now:

findroot (rootfs0,0,a)
kernel$ /platform/i86pc/kernel/$ISADIR/unix -B $ZFS-BOOTFS
module$ /platform/i86pc/$ISADIR/boot_archive

For more information, see x86: Implementation of the findroot Command.

Support for Specifying Platform by Using bootadm Command

Solaris Express Community Edition, build 87: A new -p option has been added to the bootadm command.

This option enables you to specify the platform or machine hardware class of a client system in situations where the client platform differs from the server platform, for example when administering diskless clients.

The -p option must be used with the -R option.

# bootadm -p platform -R [altroot]

The specified platform must be one of the following:

• i86pc

• sun4u

• sun4v

For more information, see the bootadm(1M) man page.

Solaris SPARC Bootstrap Process Redesigned

Solaris Express Community Edition, build 80: The Solaris SPARC bootstrap process has been redesigned to increase commonality with the Solaris x86 boot architecture.

Other enhancements include an improved boot architecture that supports booting a system from additional file system types, for example a ZFS file system or a single miniroot for installation, as well as booting from DVD, NFS, or HTTP. These enhancements increase flexibility and reduce maintenance requirements on SPARC based systems.

As part of this redesign, the Solaris boot archives and the bootadm command, previously only available on the Solaris x86 based platform, are now an integral part of the Solaris SPARC boot architecture.

The primary difference between the SPARC and x86 boot architectures is how the boot device and file are selected at boot time. The SPARC based platform continues to use the OpenBoot^TM PROM (OBP) as the primary administrative interface, with boot options selected by using OBP commands. On x86 based systems, these options are selected through the BIOS and the GRand Unified Bootloader (GRUB) menu.

Although the implementation of the Solaris SPARC boot has changed, no administrative procedures for booting a SPARC based system have been impacted. Boot tasks that are performed by the system administrator remain the same as they were prior to the boot architecture redesign.

For more information, see the boot(1M) and bootadm(1M) man pages.

For more information in this document, see Understanding the New Solaris SPARC Boot Architecture.

x86: Support for Booting the Solaris OS as a Virtualized Control Domain

Solaris Express Community Edition, build 75: In this release, the GRUB boot loader is capable of booting a Solaris release that runs with hypervisor technology. The hypervisor can securely execute multiple virtual machines simultaneously, each running its own operating system, on a single physical system. You can decide at boot time whether to run the Solaris OS as a virtualized domain0, also called a dom0, or as a stand-alone operating system.

You can run the Solaris OS as a virtualized dom0. Whether to run the Solaris OS as a virtualized dom0 or as a stand-alone operating system is a decision you can make at boot time. To run the Solaris OS as a virtualized dom0, there must first be an entry in the menu.lst file that specifies the hypervisor. The entry can be the default boot entry, or it can be an option that you select manually at boot time. Note that when you upgrade your system to a Solaris release that includes this capability, the bootadm command automatically adds a menu entry for the hypervisor to the menu.lst file.

The bootadm command installs a default boot entry in the menu.lst file that is similar to the following:

kernel$ /boot/$ISADIR/xen.gz
module$ /platform/i86xpv/kernel/$ISADIR/unix /platform/i86xpv/kernel/$ISADIR/unix -B $ZFS-BOOTFS 
module$ /platform/i86pc/$ISADIR/boot_archive

The format for entries that are used in the menu.lst file for booting the Solaris OS as a control domain differs slightly from the format that is used for other menu.lst entries. The kernel$ line must identify the hypervisor binary to use and includes any options that are accepted by the hypervisor. The first module$ line in the file identifies the Solaris kernel to use, for example unix, and include any options the unix kernel accepts. Due to an implementation detail that exists in this version of GRUB, the specified unix kernel must be named twice on the first module$ line. The second module$ line identifies the boot archive to use.

For more information, see Description of a menu.lst File That Supports Hypervisor Technology.

For more information about administering Solaris systems that support the hypervisor, see http://www.opensolaris.org/os/community/xen/docs/ and System Administration Guide: Virtualization Using the Solaris Operating System

x86: GRUB Support for Directly Loading and Booting the unix Kernel

Solaris Express Community Edition, build 57: This release includes changes to the GRUB based boot environment to enable the boot loader to directly load and boot the unix kernel.

The GRUB multiboot module is no longer used.

This implementation integrates the previous multiboot functionality directly into the platform-specific unix kernel module. These changes reduce the time, as well as memory requirements, that are needed to boot the Solaris OS on x86 based systems.

Two new keywords, kernel$ and module$, have been added to GRUB to assist in creating menu.lst entries that work with either 32-bit or 64-bit systems. In addition, the bootadm command that manages the menu.lst file has been modified to create file entries for the platform-specific unix module that is loaded by GRUB. During an upgrade, the bootadm command converts any existing multiboot menu.lst entries to unix entries.

The kernel$ and module$ keywords are identical to the kernel and module commands that are used in the GRUB multiboot implementation, with the addition of the $ISADIR keyword. This keyword provides the capability to expand to amd64 on 64-bit capable hardware. If the x86 based system is not 64-bit capable, the $ISADIR keyword is a null value (""). In this case, the system boots the 32-bit kernel.

These changes do not prevent you from booting a newer Solaris kernel with an older implementation of GRUB. Nor do the changes prevent you from booting an older Solaris kernel with a newer implementation of GRUB.

For information about booting an x86 based system with GRUB, see x86: Administering the GRUB Bootloader.

x86: Support for Using Power Button to Initiate System Shutdown

Pressing and releasing the power button on x86 based systems initiates a clean system shutdown and turns the system off. This functionality is equivalent to using the init 5 command to shut down a system. On some x86 based systems, the BIOS configuration might prevent the power button from initiating shutdown. To enable use of the power button to perform a clean system shutdown, reconfigure the BIOS.

On certain x86 based systems that were manufactured before 1999 and are running an older Solaris release, pressing the power button immediately turns off system power without safely shutting down the system. This same behavior occurs when pressing the power button on systems that are running with ACPI support that is disabled through the use of acpi-user-options.

For more information about acpi-user-options, see the eeprom(1M) man page.

Where to Find Shut Down and Boot Tasks

Use these references to find step-by-step instructions for shutting down and booting a system.

Shut Down and Boot Terminology

This section describes the terminology that is used in shutting down and booting a system.

Run levels and init states

A run level is a letter or digit that represents a system state in which a particular set of system services are available. The system is always running in one of a set of well-defined run levels. Run levels are also referred to as init states because the init process maintains the run level. System administrators use the init command or the svcadm command to initiate a run-level transition. This book refers to init states as run levels.

Boot options

A boot option describes how a system is booted.

Different boot options include the following:

• Interactive boot – You are prompted to provide information about how the system is booted, such as the kernel and device path name.

• Reconfiguration boot – The system is shutdown and rebooted to add new devices, if the devices are not hot-pluggable.The system is reconfigured to support newly added hardware or new pseudo devices.

• Recovery boot – The system is hung or an invalid entry is prohibiting the system from booting successfully or from allowing users to log in.

For terminology that is specific to GRUB based booting, see x86: GRUB Terminology.

Guidelines for Shutting Down a System

Keep the following in mind when you shut down a system:

• Use the init and shutdown commands to shut down a system. Both commands perform a clean system shutdown, which means that all system processes and services are terminated normally.

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  x86 only –

  For x86 based systems that are running at least the Solaris 10 6/06 release, you can initiate a clean system shutdown by pressing and releasing the power button. Shutting down an x86 based system in this manner is equivalent to using the init 5 command to shut down a system. On some x86 based systems, the BIOS configuration might prevent the power button from initiating a system shutdown. To use the power button, reconfigure the BIOS.

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• Use the shutdown command to shut down a server. Logged-in users and systems that mount resources from the server are notified before the server is shut down. Additional notification of system shutdowns by electronic mail is also recommended so that users can prepare for system downtime.

• You need superuser privileges to use the shutdown or init command to shut down a system.

• Both shutdown and init commands take a run level as an argument.

  The three most common run levels are as follows:

  • Run level 3 – All system resources are available and users can log in. By default, booting a system brings it to run level 3, which is used for normal day-to-day operations. This run level is also known as multiuser level with NFS resources shared.

  • Run level 6 – Stops the operating system and reboots to the state that is defined by the initdefault entry in the /etc/inittab file.

  • Run level 0 – The operating system is shut down, and it is safe to turn off power. You need to bring a system to run level 0 whenever you move a system, or add or remove hardware.

  Run levels are fully described in Chapter 16, Managing Services (Overview).

Guidelines for Booting a System

Keep the following in mind when you boot a system:

• After a SPARC based system is shut down, it is booted by using the boot command at the PROM level.

• After an x86 based system is shut down, it is booted by selecting an OS instance in the GRUB menu.

• In the Solaris 9 release and some Solaris 10 releases, after an x86 based system is shut down, it is booted by using the boot command at the Primary Boot Subsystem menu.

• A system can be rebooted by turning the power off and then back on.

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  Caution –

  This method is not considered a clean shutdown, unless you have an x86 based system that is running a Solaris release that supports this shutdown method. See x86: Support for Using Power Button to Initiate System Shutdown. Use this shutdown method only as an alternative in emergency situations. Because system services and processes are terminated abruptly, file system damage is likely to occur. The work required to repair this type of damage could be substantial and might require the restoration of various user and system files from backup copies.

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• SPARC and x86 based systems use different hardware components for booting. These differences are described in Chapter 15, x86: GRUB Based Booting (Reference).

When to Shut Down a System

The following table lists system administration tasks and the type of shutdown that is needed to initiate the task.

For examples of shutting down a server or a stand-alone system, see Chapter 10, Shutting Down a System (Tasks).

When to Boot a System

The following table lists system administration tasks and the corresponding boot option that is used to complete the task.