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Windows Boot process

What is involved in Windows Boot Process:

Windows_Booting_Procedure

  • Power is turned on.
  • The first process starting when you turn on your computer is BIOS i.e, Basic Input Output System. BIOS has two functions, to conduct POST and read MBR.
    1. POST – POST stands for Power On Self Test. POST checks all the hardware devices connected to a computer like RAM, hard disk etc and make sure that the system can run smoothly with those hardware devices. If the POST is a failure the system halts with a beep sound.
    2. Now BIOS checks the boot priority. We can set the boot priority as CD drive, hard disk or floppy drive
    3. MBR – The next duty of BIOS is to read the MBR. MBR stands for Master Boot Record and its the first sector on a hard disk. MBR
      contains the partition table and boot loader.
  • Functions of Boot loader
    Now BIOS has passed the control to boot loader and boot loader is a small program which loads kernel to computers memory. Actually there are two stages of boot loaders, stage 1 boot loader and stage 2 boot loader. MBR contains the stage 1 boot loader and stage 1 boot loader is a link to the stage 2 boot loader. The stage 2 boot loader resides in the boot partition and it loads the kernel to memory.
  • Boot files and functions
    There are three boot files in a Windows operating system and they are NTLDR, NTDETECT.COM and Boot.ini. The boot files are found in the active partition of hard disk and its normally C drive in a Windows machine.

    1. NTLDR – NTLDR stands for NT Loader and its the second stage bootloader. The path of NTLDR is C:\Windows\i386\NTLDR.
    2. Boot.ini – Boot.ini contains the configuration files of NTLDR. When the operating system is loaded we cannot pass any arguments to kernel, so those arguments are passed through boot.ini. You can edit boot.ini by opening through notepad. The path of Boot.ini is C:\boot.ini.

    3. NTDETECT.COM – This file detect hardware’s and passes information to NTLDR. Using the collected information the NTLDR creates a hardware key and this key is used to detect hardware’s. A new hardware key is generated after each reboot of the operating system and that’s why system asks to reboot after installation of a new hardware. The hardware keys created by NTLDR can be found in Windows registry at
      HKEY_LOCAL_MACHINE -> HARDWARES.

  • Kernel and its functions
    After executing the functions of boot files the control is passed to Kernel. ntoskrnal.exe is the kernel file in a Windows machine and its path is C:\Windows\system 32\ntoskrnal.exe. Kernel acts as a layer between software and hardware. The library file hal.dll (C;\Windows\system32\hal.dll) helps Kernel to interact with hardware’s. HAL stands for Hardware Abstraction Layer and this hal.dll file is
    machine specific. Now the drivers for hardware’s are loaded from the file C:\Windows\system32\config\system and the Kernel is loaded to primary memory.

  • Services and log in procedure
    When kernel is loaded in the primary memory services for each process is started and the registry entry for those services can be found at HKEY_LOCAL_MACHINE – System – Current control set – Services.
    Winlogon.exe (C:\Windows\system32\winlogon.exe) is the last service started during this process.
    Winlogon.exe starts the log in procedures of windows machine. It first calls the library file msgina.dll (C:\Windows\system32\msgina.dll). MSGINA stands for Microsoft Graphics Identification and Authentication and it provides the log in window. Now msginal.dll passes the control to LSA (Local Security Authority), it verifies the username and password from the SAM file. SAM (Security Accounts Manager) contains the information about all users created in a Windows operating system.
    Now the booting procedure is over and we have reached the desktop of Windows operating system.

Source:

  1. https://kb.acronis.com/sites/default/files/content/2006/01/1934/windows_booting_procedure.pdf
  2. http://www.slideshare.net/dominiquec/understanding-the-boot-process
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Search all files containing a specific string

How to search all files containing a specific string on Linux and Windows?

  • On Linux

    grep -rnw ‘directory’ -e “pattern”
    grep –include=\*.{txt,log} -rnw ‘directory’ -e “pattern”
    This will only search for files with .txt or .log extension.
    grep –exclude=*.txt -rnw ‘directory’ -e “pattern”
    This will exclude files with .txt extensions.

  • On Windows

    CD Location
    FINDSTR /L /S /I /N /C:”pattern” *.log

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Browse the internet via command line

How to browse the internet via command line on Linux and Windows?

  • On Linux

    lynx http://google.ca
    If you don’t have lynx on your linux installation, you will have to install it. On Linux Red hat, install it like this:
    yum list lynx (to check the availability of the package)
    yum -y install lynx (to install the package)
    you can also use: curl -0 http://yoursite/index.html to get the source code of a specific file.

  • On Windows

    start /max http://google.ca
    Will open the url using your default browser.

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Check how many CPU cores on Windows and on Linux

How to check how many CPU cores I have on Windows & Linux?

What is a core in a CPU?
In summary, a core is a small CPU or processor built into a big CPU or CPU socket. It can independently perform or process all computational tasks. From this perspective, we can consider a core to be a smaller CPU or a smaller processor within a big processor.
Today, CPUs have been two and 18 cores, each of which can work on a different task. A core can work on one task, while another core works a different task, so the more cores a CPU has, the more efficient it is.

Open a command prompt (Windows) or Terminal (Linux) and type:

  • Windows: WMIC CPU Get /Format:List
    Capture_Check_CPU_Cores
  • Linux: cat /proc/cpuinfo | grep processor | wc -l
    For more details on Linux: ls /sys/devices/system/cpu/

What does 4 CPU cores mean?
A quad-core CPU has four processing cores in a single chip. It is similar to a dual-core CPU, but has four separate processors (rather than two), which can process instructions at the same time.