COMP1321 Digital Infrastructures Richard Henson November 2013

Week 6: Boot up, Files, Storage and the Windows Registry n Objectives:  Explain how data is stored for easy retrieval on a hard disk  Explain the Windows boot-up process  Explain why user and system settings need to be configured for multi-user use and across a network  Explain the role of the registry in Windows desktop & network configuration, user settings, security

Operating System Boot Up 1. ROM-BIOS 2. Bootstrap sector/file for hard disk 3. System files from hard disk 4. Registry 5. Configuration of drivers, etc. 6. Logon…

BIOS Developments n Earlier motherboards had a single chip containing the BIOS on ROM and a writeable CMOS area  the command line interface invoked was 16-bit n More recent motherboards use EFI (Extensible Firmware Interface)  uses a 32-bit command line  only really exploited with Windows 7, and 2008 Server…

More about ROM-BIOS n n 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 to an Intel platform n BIOS program “points” to selected medium that contains a “boot loader” program »contains “master boot record” (MBR) »points to the boot partition n containing the operating system n Different media prepared in different ways »hard disk still the conventional boot medium n number of partition options so potential choice of bootable media »CDs & USBs only have one partition

Storage of Data as Files n Taken for granted, but actually a very ordered process including a minimum of:  filename  filename suffix (type of file)  filesize  address of start of file…

More about Hard Disks n Storage happens because of physical change…  magnetically active coating on a metal platter  particles move in response to magnetic field n Partitioning and Formatting are about  ordering the magnetic arms that move the particles  the particles themselves…

Structure of a Partitioned Hard Disk n Area of disk (could be whole disk) allocated for secondary storage n Formatting organises the magnetic particles on the platter so they can store data, byte-by-byte n All about orientation of particles so they store “0” or “1”… very precise!  more:

Saving to Disk n Assumes disk partitioned and formatted  resulting file organisation depends on »operating system »file system chosen n Unit of storage on disk is the sector  Traditionally, 1 sector = 512 bytes »2011 on… 1 sector = 4096 bytes! »hard disks still have very many sectors on which to store data, but smallest storage now 4K…

Partitions, Hard Disks and Multiple Operating Systems n MBR starts the disk-based boot-up  must be on the first (C:) partition n Possible to have different operating systems on the same hard disk…  varieties of Windows  varieties of Unix… n MBR systems are different on Unix and Windows  BUT…still possible to have ONE Unix partition coexisting with Windows…

Storage of User/System Settings: Windows Registry n Early Windows extended DOS text files of system & user settings:  SYSTEM.INI enhanced CONFIG.SYS  WIN.INI enhanced AUTOEXEC.BAT n Windows 95 created a two dimensional structure… known as The Registry  principles later extended in Windows NT v4 to allow system and user settings to be downloaded to local registry across the network

Viewing/Editing the Registry n REGEDT32 from command prompt…  look but don’t touch!  contents should not be changed manually unless you really know what you are doing!!! n Registry data that is loaded into memory can also be overwritten by data:  from local profiles  downloaded across the network…

System Settings n For configuration of hardware and software  different types of system need different settings  system settings for a given computer may need to be changed for particular users »e.g. refresh rate for an epileptic user can be configured when the user logs on

User Settings n More a matter of convenience for the user  mandatory profiles »users all get the same desktop settings! »anything added is lost during logoff!  roaming profiles - desktop settings preserved between user sessions »saved across the network…

Structure of The Registry? n Five basic subtrees (or hives):  HKEY_LOCAL_MACHINE : local computer info. Does not change no matter which user is logged on  HKEY_USERS : default user settings  HKEY_CURRENT_USER : current user settings  HKEY_CLASSES_ROOT : software config data  HKEY_CURRENT_CONFIG : “active” hardware profile n Each subtree contains one or more subkeys…

Location of the Windows Registry n Stored in MBR partition  usually C:  actual folder depends on Windows version… »in XP… C :\windows\system32\config folder

The Registry Files & Setting the Desktop n Six files (no file extensions!):  Software  System – hardware settings  Sam, Security »not even viewable through regedt32  Default – default user  Sysdiff – HKEY USERS subkeys n Also part of boot process: ntuser.dat »user settings that override default user

Emergency Recovery if Registry lost or badly damaged n Backup registry files created during text-based part of windows installation  also stored in: »c:\windows\system32\config »have.sav suffix  only updated if “R” option is chosen during a windows recovery/reinstall n NEVER UPDATED backup is saved to  C:\windows\repair folder  no user and software settings  reboots back to “Windows is now setting up”

Backing up the Registry n Much forgotten… an oversight that may later be much regretted!!!  can copy to tape, USB stick CD/DVD, or disk  rarely more than 100 Mb n Two options;  Use third-party backup tool »e.g  Use windows “backup” »not recommended by experts! »but already there & does work! »to copy the registry if this tool is chosen, a “system state” backup option should be selected

System Backup and Recovery n It won’t break down…  famous last words! n n Early versions of DOS/Windows did encourage backup n n 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!