Computer Service and Repair, 3rd Edition Page 674 (674 of 976)

674 Computer Service and Repair
Linux Boot Sequence
Some common versions of Linux are SUSE, Xandros, Red Hat, Caldera, and
Debian. All have graphical user interfaces available and appear similar to the
Windows screen display.
Linux is similar to the other systems in that a POST is performed and a BIOS
routine is loaded. It is common to boot from a floppy disk when using Linux,
but you may also boot from the hard drive. Like any typical startup operating
system, after the initial system startup, the Linux operating system takes over.
Linux uses a boot manager called lilo, which stands for Linux loader. Lilo looks
at the configuration file called
lilo.conf
to detect operational information. The lilo
boot manager allows the user to select other operating systems when more than
one exists on the hard drive. Linux operating systems can coexist with Microsoft
Windows operating systems. Once the Linux kernel loads, the system runs the
init program. The init is the system initialization, similar to DOS or Windows.
All the system processes, such as the keyboard, mouse, and network connections,
require initialization.
Data Recovery Techniques
Many times data on a nonfunctioning hard drive is not actually lost, although
it cannot be directly accessed. Think about the causes of failure for a hard drive.
They include the electronics board mounted on the hard drive, the mechanical
parts inside the drive, or simply a boot sector failure. If you can still see the drive
directory on drive
C
when using a boot disk, chances are excellent for recovering
the data.
One of the most common ways to recover data is with software. There are
a number of third-party programs out there designed to read disks that show
as bad. Figure 15-29 shows a disk being accessed by Norton Disk Editor. It can
examine the disk and display the sectors in your choice of ASCII, binary, or
hexadecimal code. Sections can then be copied to another disk.
Mechanical and electronic repairs should be left to the specialist. Many
businesses specialize in this type of data recovery. An electronic circuit board
controller mounted on the drive could fail. It can be replaced, but it takes a skilled
electronics technician. The circuit conductors are very fragile and easily broken.
Also, disk drive platters can be removed and installed on other drives. However,
it takes special tools, training, and a clean room (which is not just a room that
is clean). A clean room is a room where dust and foreign particles have been
completely eliminated.
clean room
a room where dust
and foreign particles
have been completely
eliminated.

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Extracted Text (may have errors)

674 Computer Service and Repair
Linux Boot Sequence
Some common versions of Linux are SUSE, Xandros, Red Hat, Caldera, and
Debian. All have graphical user interfaces available and appear similar to the
Windows screen display.
Linux is similar to the other systems in that a POST is performed and a BIOS
routine is loaded. It is common to boot from a floppy disk when using Linux,
but you may also boot from the hard drive. Like any typical startup operating
system, after the initial system startup, the Linux operating system takes over.
Linux uses a boot manager called lilo, which stands for Linux loader. Lilo looks
at the configuration file called
lilo.conf
to detect operational information. The lilo
boot manager allows the user to select other operating systems when more than
one exists on the hard drive. Linux operating systems can coexist with Microsoft
Windows operating systems. Once the Linux kernel loads, the system runs the
init program. The init is the system initialization, similar to DOS or Windows.
All the system processes, such as the keyboard, mouse, and network connections,
require initialization.
Data Recovery Techniques
Many times data on a nonfunctioning hard drive is not actually lost, although
it cannot be directly accessed. Think about the causes of failure for a hard drive.
They include the electronics board mounted on the hard drive, the mechanical
parts inside the drive, or simply a boot sector failure. If you can still see the drive
directory on drive
C
when using a boot disk, chances are excellent for recovering
the data.
One of the most common ways to recover data is with software. There are
a number of third-party programs out there designed to read disks that show
as bad. Figure 15-29 shows a disk being accessed by Norton Disk Editor. It can
examine the disk and display the sectors in your choice of ASCII, binary, or
hexadecimal code. Sections can then be copied to another disk.
Mechanical and electronic repairs should be left to the specialist. Many
businesses specialize in this type of data recovery. An electronic circuit board
controller mounted on the drive could fail. It can be replaced, but it takes a skilled
electronics technician. The circuit conductors are very fragile and easily broken.
Also, disk drive platters can be removed and installed on other drives. However,
it takes special tools, training, and a clean room (which is not just a room that
is clean). A clean room is a room where dust and foreign particles have been
completely eliminated.
clean room
a room where dust
and foreign particles
have been completely
eliminated.

Help

Chapter 15 PC Troubleshooting 675
Preparation for Installing or Upgrading an
Operating System
Before installing a new operating system, several appropriate practices should
be followed for the ideal setup:
✔ Check for viruses.
✔ Defrag the drive.
✔ Read the
readme.txt
file.
✔ Check the operating system’s Web site for latest updates, known installation
problems, hardware compatibility lists, patches, and updates.
If you are upgrading an existing system, be sure to backup existing system
data. You are probably tired of hearing “back up the system data,” but it is
the only way to rebuild a destroyed system. There are two commonly accepted
methods of backing up files: incremental and differential.
The difference between the two is determined by the archive bit. The archive
bit is designed to indicate if a file has been backed up or not. This issue is
important on large data systems where backups are performed daily to ensure
against data loss.
An incremental backup requires a disk or tape for each daily backup. When
performing an incremental backup, only the changes in data since the last
incremental or last full backup are copied. A copy of the last full data backup
plus each incremental backup in sequence must be used to reconstruct an entire
collection of data, Figure 15-30. When performing a differential backup, all
the data changes are copied since the last full backup. Only one disk or tape is
needed to perform the differential backup because it copies all changes in data
since the last full backup was performed. To restore the data, you need only the
last full backup and the last differential backup.
Figure 15-29.
Data on a hard drive
that stops working
can often be accessed
using special
software. Here a file
is being viewed in
Norton’s Disk Editor.
incremental backup
operation that backs
up select files that
have changed since
the last backup of
files. The archive bit
is reset.
differential backup
operation that
saves files that have
changed since the
last full backup of all
files. The archive bit
is not reset.

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Chapter 15 PC Troubleshooting 673
the drivers and devices loaded so far and through the rest of the boot operation.
This information is used for the
Last known good configuration
boot option when
troubleshooting the system or attempting to recover from a system failure. The
kernel then loads the Session Manager (smss.exe).
Session Manager phase
In this phase, the boot process switches from text mode to graphic mode. A
progress bar appears at the bottom of the screen. The session manager continues
to run in the background until the computer is shut down.
The Session Manager starts and runs an abbreviated version of Chkdsk
and determines if the system volumes and partitions are in working order. The
Session Manager is also responsible for loading the page file or virtual memory.
The page file supplements the amount of RAM installed on the computer.
Microsoft does not allow third-party venders’ software applications to
directly access hardware and certain operating system files. But when access is
needed by the third-party software applications, the Session Manager manages
the activities. If the startup process fails here, you will see a Microsoft system
blue screen error. Recall that a blue screen error is a full-screen text message
describing the error on a plain, blue background. There will be a cryptic error
code that can be used to conduct a search at the Microsoft Web site to find the
most likely cause. Microsoft has a very extensive collection of troubleshooting
information at their TechNet Web site. The last phase of the startup process is
called the logon phase.
Logon phase
In this phase, the windows logon file (winlogon.exe) is executed, and the
Windows Logon dialog box appears. A user typically enters his or her logon
name and password to proceed to the operating system desktop.
After a successful logon, the
lsass.exe
file loads and runs. This file is the Local
Security Authority (LSA). Then, the service subsystem file,
services.exe
loads
and runs. The exact services loaded and started is determined by the computer’s
configuration and the user’s credentials. Only the services the user is allowed
to access will start. If there is only one default user and the computer is not
connected to a network with a server, the user will be able to access and run all
services for the computer. If a user has a limited account, they will only be able to
run services allocated by the system administrator.
Startup programs are loaded and run at this point. Any problems such as the
computer freezing up or a very long delayed appearance of the user desktop are
associated with the startup files and services. If a computer user installs many
programs over a period of time, the appearance of the desktop after completing
logon will take more time.
After a successful logon, the boot process is considered a success. The registry
is updated and will become the registry reference for the “Last known good
configuration.” A failure of the system after logon is usually a sign of a failed
service or a software startup application.
One of the best utilities for analyzing failures after logon is the System
Configuration Utility (msconfig.exe). You can select and isolate services and
software applications that might be causing the problem.

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