Troubleshoot Boot Issues

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Once the POST tests are complete, the firmware searches for devices as specified in the boot sequence.

• If the first device in the sequence is not found, the system attempts to boot from the next device
  • E.g., if there is no fixed disk, the boot sequence checks for a USB-attached drive
• If no disk-based boot device is found, the system might attempt to boot from the network
• If no boot device is found, the system displays an error message and halts the boot process
• If the system attempts to boot from an incorrect device
  • check that the removable drives do not contain media that are interfering with the boot process
  • and that the boot device order is correctly configured
• If a fixed disk is not detected at boot, try to check that it is powering up
  • Drive activity is usually indicated by an LED on the front panel of the system unit case
  • If this is inactive, check that the drive has a power connector attached
  • If the PC has no LEDs, or you suspect that they may be faulty, it is usually possible to hear a hard disk spinning up
• Once you have determined that the drive is powering up, try the following:
  • Check that data cables are not damaged and that they are correctly connected to the drive
  • If the drives are connected to a motherboard port, check that it has not been disabled by a jumper or via system setup

Troubleshoot Boot Sector Issues

If you can rule out issues with power and cabling, suspect an issue with the device’s boot sector and files.

• Corruption due to faults in the disk unit, power failure, incorrect installation of multiple operating systems, or malware will prevent the disk from working as a boot device
• two ways of formatting the boot information:
  • legacy master boot record (MBR) scheme, the MBR is in the first sector of the first partition.
    • Partitions allow a single disk device to be divided into multiple logical drives
    • The first sector contains information about the partitions on the disk plus some code that points to the location of the active boot sector
    • The boot sector is located either on the sector after the MBR or the first sector of each other partition
      • It describes the partition file system and contains the code that points to the method of booting the OS
      • Typically, this will be the Boot Configuration Data (BCD) store for a Windows system or GRUB or LILO Linux boot managers
    • Each primary partition can contain a boot sector, but only one of them can be marked active
  • globally unique ID (GUID) partition table (GPT) boot scheme, the boot information is not restricted to a single sector but still serves the same basic purpose of identifying partitions and OS boot loaders.
• Whether the disk is using an MBR or GPT partitioning scheme, damage to these records results in boot errors such as “Boot device not found,” “OS not found,” or “Invalid drive specification”
  • If this problem has been caused by malware, the best way to resolve it is to use the boot disk option in your antivirus software
    • will include a scanner that may detect the malware that caused the problem in the first place and contain tools to repair the boot sector
  • If you don’t have the option of using a recovery disk created by the antivirus software, you can try to use the repair options that come with the OS setup disk

Troubleshoot OS Errors and Crash Screens

If a boot device is located, the code from the boot sector on the selected device is loaded into memory and takes over from the system firmware.

• boot sector code loads the rest of the operating system files into system memory
• Error messages received after this point can usually be attributed to software or device driver problems rather than physical issues with hardware devices

If there is a serious fault, a Windows system will display a blue screen of death (BSOD).

• typically indicates that there is:
  • a system memory fault
  • a hardware device/driver fault
  • corruption of operating system files
• Use a camera to scan the quick response (QR) error code and open the URL with further information
• error should also be written to the System log with BugCheck as the source
• From the event description, use the first hex value, such as 0x0a, to find information about the event online
• system will generate a memory dump that you can forward for analysis if you have a support contract