COMP1321COMP1321

Digital InfrastructureDigital Infrastructure

Richard HensonRichard Henson

FebruaryFebruary 20122012

Week 6: Boot up and the Week 6: Boot up and the Windows RegistryWindows Registry

Objectives:Objectives: Explain the Windows boot-up processExplain the Windows boot-up process Explain why user and system settings need to be Explain why user and system settings need to be

configured for multi-user use and across a networkconfigured for multi-user use and across a network Explain the role of the registry in Windows desktop Explain the role of the registry in Windows desktop

and network configuration, user settings, and and network configuration, user settings, and securitysecurity

Operating System Boot UpOperating System Boot Up

1.1. ROM-BIOSROM-BIOS2.2. Bootstrap sector/file for hard diskBootstrap sector/file for hard disk3.3. System files from hard diskSystem files from hard disk4.4. RegistryRegistry5.5. Configuration of drivers, etc.Configuration of drivers, etc.6.6. Logon…Logon…

BIOS DevelopmentsBIOS Developments Earlier motherboards had a single chip Earlier motherboards had a single chip

containing the BIOS on ROM and a writeable containing the BIOS on ROM and a writeable CMOS areaCMOS area the command line interface invoked was 16-bitthe command line interface invoked was 16-bit

More recent motherboards use EFI More recent motherboards use EFI (Extensible Firmware Interface)(Extensible Firmware Interface) uses a uses a 32-bit command line32-bit command line only really exploited with Windows 7, and 2008 only really exploited with Windows 7, and 2008

Server…Server…

More about ROM-BIOS Not all ROM…

basic operating system programs in the ROM part

Configurable CMOS settings allow configuration and tuning of devices connected directly to the motherboard

including secondary storage boot sequence…

CMOS settings

OS programs

More about booting More about booting to an Intel platformto an Intel platform

BIOS program “points” to selected medium BIOS program “points” to selected medium that contains a “boot loader” programthat contains a “boot loader” program

» contains “master boot record” (MBR)contains “master boot record” (MBR)» points to the boot partition points to the boot partition

containing the operating systemcontaining the operating system

Different media prepared in different waysDifferent media prepared in different ways» hard disk still the conventional boot mediumhard disk still the conventional boot medium

number of partitions so potential choice of bootable medianumber of partitions so potential choice of bootable media

» CDs & USBs only have one partitionCDs & USBs only have one partition

Partitions, Hard Disks and Partitions, Hard Disks and Multiple Operating SystemsMultiple Operating Systems

MBR must be on the first (C:) partitionMBR must be on the first (C:) partition Possible to have different operating systems Possible to have different operating systems

on the same hard disk…on the same hard disk… varieties of Windowsvarieties of Windows varieties of Unix…varieties of Unix…

BUT…BUT… Master Boot Record systems different on Unix and Master Boot Record systems different on Unix and

WindowsWindows still possible to have ONE Unix partition…still possible to have ONE Unix partition…

Storage of User/System Storage of User/System Settings: Windows RegistrySettings: Windows Registry

Early Windows extended DOS text files of Early Windows extended DOS text files of system & user settings:system & user settings: SYSTEM.INI enhanced CONFIG.SYSSYSTEM.INI enhanced CONFIG.SYS WIN.INI enhanced AUTOEXEC.BATWIN.INI enhanced AUTOEXEC.BAT

Windows 95 created a two dimensional Windows 95 created a two dimensional structure… known as The Registrystructure… known as The Registry principles later extended in Windows NT v4 to principles later extended in Windows NT v4 to

allow system and user settings to be downloaded allow system and user settings to be downloaded to local registry to local registry across the networkacross the network

Viewing/Editing the RegistryViewing/Editing the Registry

REGEDT32 from command prompt…REGEDT32 from command prompt…look but don’t touch!look but don’t touch! contents should not be changed manually unless contents should not be changed manually unless

you really know what you are doing!!!you really know what you are doing!!!

Registry data that is loaded into Registry data that is loaded into memory can also be overwritten by memory can also be overwritten by data:data:from local profilesfrom local profilesdownloaded across the network…downloaded across the network…

System SettingsSystem Settings

For configuration of hardware and For configuration of hardware and softwaresoftwaredifferent types of system need different different types of system need different

settingssettingssystem settings for a given computer may system settings for a given computer may

need to be changed for particular users need to be changed for particular users » e.g. refresh rate for an epileptic user can be e.g. refresh rate for an epileptic user can be

configured when the user logs onconfigured when the user logs on

User SettingsUser Settings

More a matter of convenience for the userMore a matter of convenience for the user mandatory profilesmandatory profiles

» users all get the same desktop settings!users all get the same desktop settings!» anything added is lost during logoff!anything added is lost during logoff!

roaming profiles - desktop settings preserved roaming profiles - desktop settings preserved between user sessionsbetween user sessions» saved across the network…saved across the network…

Structure of The Registry?Structure of The Registry?

Five basic subtrees (or hives):Five basic subtrees (or hives): HKEY_LOCAL_MACHINEHKEY_LOCAL_MACHINE : local computer info. : local computer info.

Does not change no matter which user is logged onDoes not change no matter which user is logged on HKEY_USERSHKEY_USERS : default user settings : default user settings HKEY_CURRENT_USERHKEY_CURRENT_USER : current user settings : current user settings HKEY_CLASSES_ROOTHKEY_CLASSES_ROOT : software config data : software config data HKEY_CURRENT_CONFIGHKEY_CURRENT_CONFIG : “active” hardware : “active” hardware

profileprofile

Each subtree contains one or more subkeys…Each subtree contains one or more subkeys…

Location of the Windows RegistryLocation of the Windows Registry Stored in MBR partitionStored in MBR partition

usually C: usually C: actual folder depends on Windows actual folder depends on Windows

version… version… » in XP… Cin XP… C:\windows\system32\config folder:\windows\system32\config folder

The Registry Files & The Registry Files & Setting the DesktopSetting the Desktop

Six files (no file extensions!):Six files (no file extensions!): SoftwareSoftware System – hardware settingsSystem – hardware settings Sam, SecuritySam, Security

» not even viewable through regedt32not even viewable through regedt32

Default – default userDefault – default user Sysdiff – HKEY USERS subkeysSysdiff – HKEY USERS subkeys

Also part of boot process: ntuser.datAlso part of boot process: ntuser.dat» user settings that override default useruser settings that override default user

Emergency Recovery if Emergency Recovery if Registry lost or badly damagedRegistry lost or badly damaged Backup registry files created during text-based Backup registry files created during text-based

part of windows installationpart of windows installation alsoalso stored in: stored in:

» c:\windows\system32\configc:\windows\system32\config» have .sav suffixhave .sav suffix

only updated if “R” option is chosen during a only updated if “R” option is chosen during a windows recovery/reinstallwindows recovery/reinstall

NEVER UPDATED backup is saved toNEVER UPDATED backup is saved to C:\windows\repair folderC:\windows\repair folder no user and software settingsno user and software settings reboots back to reboots back to “Windows is now setting up”“Windows is now setting up”

Backing up the RegistryBacking up the Registry

Much forgotten… an oversight that may later Much forgotten… an oversight that may later be much regretted!!!be much regretted!!! can copy to tape, USB stick CD/DVD, or diskcan copy to tape, USB stick CD/DVD, or disk rarely more than 100 Mbrarely more than 100 Mb

Two options;Two options; Use third-party backup toolUse third-party backup tool

» e.g e.g http://www.acronis.co.uk Use windows “backup”Use windows “backup”

» not recommended by experts!not recommended by experts!» but already there & does work!but already there & does work!» to copy the registry if this tool is chosen, a “system state” to copy the registry if this tool is chosen, a “system state”

backup option should be selectedbackup option should be selected

System Backup and RecoverySystem Backup and Recovery It won’t break down…It won’t break down…

famous last words!famous last words! Early versions of DOS/Windows did

encourage backup From Windows NT v4 onwards, Microsoft

made a real effort…problem was, you had to either be an avid reader

or go on a course to find out where the backup option are and where to use them!

Contrast with Apple approach… » assured that the system will handle it» fine until the system itself crashes!