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Two Hidden OS Boot Items Not in the Setup Boot Option List
Overview
- Hardware configuration
TaiShan 200 server
- Symptom
Check the OS boot options, and find two more boot items that are not displayed in the list of setup boot options, as shown in the following figure. However, these two hidden boot items are not displayed for the x86 OS.
Key Process and Cause Analysis
- Key Process
Start the server to access the OS. Run the efibootmgr command in the OS to check the boot option information. Two boot items BootmangerMenuApp and ByoUiApp are found.
- Root Cause Analysis
- BootManagerMenuApp and ByoUiApp correspond to the Boot tab (opened by pressing F2) and the BIOS Setup screen (opened by pressing F4 or DEL) respectively. The two items does not affect the function.
- The BootManager/Setup code of the ARM BIOS is based on the open source EDK II. The open source code manages the Setup menu as a standard boot item. Therefore, Bootxxxx variables are generated and added to the BootOrder variable.
After verification, it is found that efibootmgr reads the BootOrder variable and displays not only Bootxxxx variables included in the BootOrder list, but also other Bootxxxx variables (not in the BootOrder list) in the variable area.