Dual system boot problems after the repair system update

Yesterday because of a system update, I hung up the dual system.

Update the system before the situation:

1. UEFI boot mode
2. ubuntu windows dual system
3. UEFI first start ubuntu, ubuntu boot menu has windows startup items. But the windows of the BCD configuration file is not set ubuntu.
4. Before starting UEFI-term there is no clear set windows startup items
   (because there has been no normal manual start over). But SSDs ESP partition /EFI/Boot/bootx64.efi are windows boot manager (if you choose (the default or manually), UEFI Boot searches for the first block format in the hard disk from the hard disk to FAT / FAT32 partition, namely ESP partition), UEFI will load the default boot manager, that if you choose to manually start from a solid state drive, open windows.

This is the cause boot problems arise update the system status after the update is

1. windows ubuntu dual system
2. UEFI boot missing in ubuntu, windows update adds a UEFI boot entry and because the windows can not be detected by other systems, resulting in the loss of ubuntu guide

The ultimate solution:

Adding Startup Items

The default is UEFI boot, which is the start menu windows linux system has a method.

Since UEFI in the system startup items missing, you can use EasyUEFI add a UEFI boot entry, can be downloaded at the following link EasyUEFI .
Open EasyUEFI, select Manage EFI boot entry, create a new item, fill type and description, select the type of startup items corresponding to the type of system, described casually, and the rest is to choose the target partition and file path.

UEFI boot entry way will be stored on a FAT disk partition format, partition is not, I have a 260M, in establishing the system boot disk may be named as ESP or EFI, with these DiskGenius can easily see, In addition to viewing the partition, behind DG can also be used to change the ESP partition repair guide.
! [Insert Picture description here] (https://img-blog.csdnimg.cn/20200311182444488.png

This is my computer FAT format partitions, called SYSTEM_DRV, watch folders can be seen.

After the press f12 boot into the selection interface UEFI boot entry. UEFI boot into or from disk to boot from the startup items that have been created. From here https://www.jianshu.com/p/9166e8c00ca2 reference picture (because too lazy restarted)

selected from the disk boot, UEFI will choose to search the EFI partition from disk, use / EFI under this partition / Boot /bootx64.efi as the default boot manager, the two entries in the above chart starts.
Choose from the startup items that have been created boot, UEFI ie, the target system will boot manager to start from the boot file to start the next step of the records.

I know that this step is like to engage in: 1 Locate the ubuntu system startup items with EasyUEFI 2. Add the Boot Manager EFI partition. Because of ubuntu grub boot startup information contained windows, so windows can be started.

Start with ubuntu using grub2, in the / EFI / ubuntu of ubuntu grubx64.efi file is the startup manager, EasyUEFI select the file path.
After adding startup items startup items top, you can log normal ubuntu and windows up.

Modify the windows of the BCD configuration file

Use startup items start windows startup process is as follows:
UEFI -----> EFI partition (FAT format) -----> \ EFI \ Microsoft \ Boot \ bootmgfw.efi (windows boot manager) ---- -> read the BCD configuration file ---------> BCD configuration options based on the kernel to load the file \ Windows \ system32 \ winload.exe.
Under the guidance of fashion Legacy + MBR, EasyBCD is the BCD by changing the contents of the file, select the appropriate startup items, but in UEFI boot, EasyBCD is prohibited to add linux boot. DG can be used to copy out the BCD file in the Microsoft folder, and then change the contents of BOOTICE BCD file.

Refer to the following link to change the configuration of Windows BCD file
http://www.upantool.com/jiaocheng/boot/9403.html

I think that using intelligent editing mode better point to start the boot manager to select the file system of the target, and the file path is the same as the first method, after the BCD file modifications to restart the windows you can see a selection menu at startup.

to sum up:

Cause of the problem is the system update when windows get rid of the UEFI boot, but unlike the linux grub2 boot disk can be detected in the same file system and added to the start menu, was a result of the UEFI boot ubuntu lost.

Originally If legacy + mbr boot, use easyBCD can easily add a boot ubuntu in windows of BCD file. But now with the computer using the boot UEFI + gpt is, easyBCD not supported, so engage them took some time. Way to sort out the information, while sharing in the future for inspection.

windows boot mode

There are mainly two main guide way windows: legacy BIOS and UEFI BIOS, there are two disk partition table format: MBR and GPT

MBR

Supports windows operating system MBR partition format up to four primary partitions or three primary partitions an extended partition, the partition can also be extended into logical partitions. MBR partition table is not larger than 2.2TB support partitioning of a hard disk or some manufacturers to upgrade the sector 4KB, the upper limit of the effective capacity of the MBR rose to 16TB

GPT

GPT partition format can support up to 128 primary partitions, the maximum capacity of up to 18EB

Generally a combination of pilot mode and the partition table, there are two, i.e., Legacy + MBR UEFI + GPT. Because, Legacy format MBR partition can be identified, does not identify the GPT partition format. UEFI two kinds of partition format can be identified, but Microsoft can only limit under UEFI boot mode will install windows to GPT disk.

Guiding principle

bootloader:
Broadly speaking equal BIOS boot manager + + + boot file loader
BIOS has Legacy UEFI
boot manager such as windows of bootmgfw.efi grub boot grubx64.efi
startup files such as windows of winload.exe

In a narrow sense means the bootloader and boot manager startup configuration file.

Legacy + MBR boot principle
boot process: Power -> Legacy BIOS-> MBR-> DPT- > PBR-> Bootmgr (vista start) / NTLDR-> BCD (vista Start) /boot.ini-> Winload.exe-> load the kernel -> windows vista / windows xp

UEFI+GPT引导原理
引导过程：上电–>UEFI–>GPT分区表–>EFI分区–>\efi\Microsoft\boot\bootmgfw.efi–>efi\Microsoft\BCD→\Windows\system32\winload.efi。

Reference documents:

1. https://blog.csdn.net/liao20081228/article/details/82591728
2. https://blog.csdn.net/li_qing_xue/article/details/79228867
3. https://www.jianshu.com/p/9166e8c00ca2
4. https://www.cnblogs.com/sddai/p/6354289.html
5. https://blog.csdn.net/donglany/article/details/79961938
6. https://bbs.deepin.org/forum.php?mod=viewthread&tid=147753&extra=