Boot process windows 7 pdf

GRUB was the predominantly-used bootloader for Linux in the s and early s, designed to load not just Linux, but any operating system implementing the open multiboot specification for its kernel. As these values could be changed by recompiling GRUB with different options, different Linux distributions had this file located under different names in different directories. GRUB 2 is a powerful, modular bootloader more akin to an operating system than a bootloader. The grub. As previously mentioned, the stage of the boot process is a little more involved than the previous steps, primarily due to the additional complexity of reading the filesystem.

The bootloader must also obtain information about the underlying machine hardware either via the BIOS or on its own in order to correctly load the desired operating system from the correct partition and provide any additional files or data that might be needed. The bootloader process is certainly a lot more nuanced and complicated than most realize, and it has both been designed and evolved to work in a fairly-standardized fashion across different platforms and under a variety of operating systems.

The individual components of the bootloader are, by and large, self-sufficient and self-contained. They can be swapped out individually without affecting the whole, meaning you can add disks and boot from different devices without worrying about upsetting existing configurations and operating systems.

When working properly, the boot process is a well-oiled machine, but when disaster strikes, it can be a very difficult process to understand and debug.

Some resources that can come handy when troubleshooting the bootloader are listed below:. These additional articles and resources in our wiki and from other websites online contain additional information relevant to this topic:. Over time and with better technology, erasable ROM chips were developed that could be cleared by placing them in a box and blasting them with a dosage of UV ultraviolet radiation, then reprogramming their contents with ROM chip programming hardware.

When that got old and tiring, electrically-erasable programmable ROM EEPROM for short was developed — with it, an electronic signal on specially-selected pins of the EEPROM chip would trigger an erase, and the chip could be programmed directly from where it was located on the motherboard. Easy-peasy-lemon-squeezy, as my wife would say!! Depending on the operating system and platform, the bootstrap code might actually only be anywhere from to bytes as parts of that region might be set aside for other purposes, such as the disk signature and disk timestamp.

On most modern operating systems, is the upper limit as the last 6 bytes are set aside for the 4-byte disk signature at offset 0x01B8 and a 2-byte field indicating the read-write state of the drive at offset 0x01BC with 0x00 indicating read-write and 0x5A5A indicating a read-only drive. What that means is that technically the actual bit indicating that a partition is bootable can actually be present set to a value of 0x80 one more than one or all!

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:.

Common performance vulnerabilities are described in the whitepaper as well. Still, it might require more tools like parallel network traces and additional debug logs such as Gpsvc logging to fully analyze a problem.

If the WinLogonInit phase takes a long time, you can use the Winlogon graph for further analysis. In this example the Group Policy processing took around seconds to complete, before the Windows desktop could be loaded.

While the Winlogon graph does not explain why it took seconds to complete GPO processing which could be related to network issues, policy settings, GPO preferences, scripts, and so on , your can see where to investigate further. The PostBoot phase includes all background activity that occurs after the desktop is ready. The user can interact with the desktop, but the system might still be starting services, tray icons, and application code in the background, potentially having an impact on how the user perceives system responsiveness.

One way to analyze the prefetcher activities is to run xperf. The above should give you some insight into where to start looking for issues during the Windows boot phase, as it will help you identify the correction section to start troubleshooting. A recommendation is to check the hardware platform thoroughly by updating the BIOS and checking hard drive performance with benchmarking tools prior to searching for the problem on the OS layer.

Office Office Exchange Server. If yes, then it offers a menu with the names of the OSs. When you select the OS, it will load the right program, i. The kernel uses the drivers to talk to the hardware and do rest of the things required for the boot process to continue.

Once that has been read, the control is taken by the system manager process. It loads up the UI, the rest of the hardware and software. When the computer starts, it first finds the operating system bootloader. When a computer equipped with UEFI starts, it first verifies that the firmware is digitally signed.

I hope this information helped you to learn more about the Windows 10 Boot process. How satisfied are you with this reply? Thanks for your feedback, it helps us improve the site.