System Administration Guide: Basic Administration

x86: Boot Process

The following table describes the boot process on x86 based systems.

Table 16–2 x86: Description of the Boot Process

Boot Phase 



1. When the system is turned on, the BIOS runs self-test diagnostics to verify the system's hardware and memory. The system begins to boot automatically if no errors are found. If errors are found, error messages are displayed that describe recovery options. 

The BIOS of additional hardware devices are run at this time. 


2. The BIOS boot program tries to read the first disk sector from the boot device. This first disk sector on the boot device contains the master boot record mboot, which is loaded and executed. If no mboot file is found, an error message is displayed.

Boot Programs 

3. The master boot record, mboot, contains disk information needed to find the active partition and the location of the Solaris boot program, pboot, loads and executes pboot, mboot.


4. The Solaris boot program, pboot, loads bootblk, the primary boot program. The purpose of bootblk is to load the secondary boot program, which is located in the UFS file system.


5. If there is more than one bootable partition, bootblk reads the fdisk table to locate the default boot partition, and builds and displays a menu of available partitions. You have a 30 seconds to select an alternate partition from which to boot. This step occurs only if there is more than one bootable partition present on the system.


6. bootblk finds and executes the secondary boot program, boot.bin or ufsboot, in the root (/) file system. You have five seconds to interrupt the autoboot to start the Solaris Device Configuration Assistant.


7. The secondary boot program, boot.bin or ufsboot, starts a command interpreter that executes the /etc/bootrc script. This script provides a menu of choices for booting the system. The default action is to load and execute the kernel. You have a 5–second interval to specify a boot option or to start the boot interpreter.

Kernel initialization 

8. The kernel initializes itself and begins loading modules by using the secondary boot program (boot.bin or ufsboot) to read the files. When the kernel has loaded enough modules to mount the root (/) file system, the kernel unmaps the secondary boot program and continues, using its own resources.


9. The kernel creates a user process and starts the /sbin/init process, which starts other processes by reading the /etc/inittab file.


10. In this Oracle Solaris release, the /sbin/init process starts /lib/svc/bin/svc.startd, which starts system services that do the following:

  • Check and mount file systems

  • Configure network and devices

  • Start various processes and perform system maintenance tasks

In addition, svc.startd executes the run control (rc) scripts for compatibility.