What are the booting files

That is, before the operating system has loaded. However, there are two types that we need to cover. One set are the files Windows requires in order to boot successfully, that are stored on the hard drive. The other are the bootable files that are stored on other devices that run before the operating system starts. When the Windows OS is first installed, certain files are placed on the hard drive that are required to be there for the operating system to load, whether in Normal Mode or Safe Mode.

When one or more of these boot files are missing, it's common to have a hiccup during startup, where you normally see some kind of error related to the missing file, like " BOOTMGR is missing. See this page for a more comprehensive listing of the boot files required to start different versions of Windows. Under normal conditions, a computer is configured to boot to a hard drive that stores the operating system, like Windows.

When the computer first boots up, the proper boot files mentioned above are read and the operating system can load from the drive. From there, you can open regular, non-bootable files like your images, documents, videos, etc. However, in some circumstances, it's necessary to boot to a device other than the hard drive, like a flash drive or CD.

When the boot sequence is properly changed, and the device is configured to be booted from, you can consider those files "bootable files" since they run at boot time. This is necessary when doing things like reinstalling Windows from a disc or flash drive , running bootable antivirus software , testing the computer's memory , partitioning the hard drive with tools like GParted , wiping all the data from the HDD , or any other task that involves manipulating or reading from the hard drive without actually booting to it.

Once there, you can change the boot order in BIOS to boot to the optical disc drive instead of the hard drive. What happens next is that instead of the computer looking for boot files on the hard drive, it looks for boot files on the disc, and then loads what it finds; AVG Rescue CD, in this case.

To reiterate the difference between boot files and regular computer files, consider that you could install a different AVG program, like the AVG AntiVirus desktop version, onto your computer's hard drive. To run it, you'd need to change the boot order to launch the hard drive's operating system. Windows boot configuration data BCD can be considered a database for boot-time configuration data. In many cases, it does not have a drive letter assigned to it.

Actively scan device characteristics for identification. Before Windows can be booted, its boot loader needs to be found. The Windows boot loader is part of the Windows operating system, which is responsible for starting Windows. Keep in mind that the MBR as well as the VBR boot code executes in real mode as bit instructions, so there are no protection mechanisms in place. After the protected mode has been loaded, another boot manager is loaded into memory, which actually boots the Windows operating system.

This is why the NTLDR program is used to switch to the protected mode and execute the protected mode boot manager. Once the NTLDR is executed, it must access the file system on the boot drive to access the files that it needs.

It first tries to find the hibernation file hiberfil. If the hibernation file is not found, it reads the boot. After that, the Ntdetect. Finally, the Ntoskrnl. The picture below shows the contents of this file:. We can take a look at all the options we can enter into the boot.

On the picture below, we can see the contents of the MBR, dumped with dd and find Linux commands:. Notice that there are two partitions and that the first one is active: this is the partition where the Bootmgr is located. Notice that the Bootmgr file is present on the picture above?

This is the file that gets loaded into memory and executed, which boots the Windows operating system. Keep in mind that Bootmgr is still a bit program, which must be used to switch from real to protected mode. The whole booting process of newer versions of Windows operating systems can be seen on the picture below, which was taken from [2]:.

The boot loader located on that partition then loads the bit Bootmgr, which in turn loads the bit Bootmgr, which then loads the winload. All of them are then used to load the NT kernel. The Bootmgr must also load the configuration files located in the D:Boot directory.

The picture below lists all the files in it:. In Windows, we can use the tool bcdedit. The picture below shows the Windows boot manager and Windows boot loader, which are displayed if we run the bcdedit. When booting the operating system, all of the Windows Boot Loaders are displayed to us and we can choose the one we would like to boot.

If only one boot loader is present as on the picture above , then the screen presenting us with the options to boot from is never shown, because the only option is used. A lot of interesting stuff also happens when the system is being booted, like the ntoskrnl.

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Privacy policy. The Boot. The following sample shows the content of a typical Boot. The [boot loader] section contains option settings that apply to all boot entries on the system. The options include timeout , the boot menu time-out value, and default , the location of the default operating system. The [operating systems] section is comprised of one or more boot entries for each operating system or bootable program installed on the computer. A boot entry is a set of options that defines a load configuration for an operating system or bootable program.

The boot entry specifies an operating system or bootable program and the location of its files. It can also include parameters that configure the operating system or program.