windows:
以管理员身份打开cmd，执行：
bcdedit /enum firmware
====
固件启动管理器
---------------------
标识符 {fwbootmgr}
displayorder {6e9edf43-4038-11ef-b884-806e6f6e6963}
{bootmgr}
{24f342ed-c536-11ed-ae87-bfc294c32d5b}
{24f342ee-c536-11ed-ae87-bfc294c32d5b}
{24f342ef-c536-11ed-ae87-bfc294c32d5b}
timeout 0
Windows 启动管理器
--------------------
标识符 {bootmgr}
device partition=\Device\HarddiskVolume6
path \EFI\Microsoft\Boot\bootmgfw.efi
description Windows Boot Manager
locale zh-CN
inherit {globalsettings}
flightsigning No
default {current}
resumeobject {9d5fbce8-bb84-11ef-bcd8-b97ad1302669}
displayorder {current}
toolsdisplayorder {memdiag}
timeout 30
固件应用程序(101fffff)
-------------------------------
标识符 {24f342ed-c536-11ed-ae87-bfc294c32d5b}
description EFI USB Device
固件应用程序(101fffff)
-------------------------------
标识符 {24f342ee-c536-11ed-ae87-bfc294c32d5b}
description EFI DVD/CDROM
固件应用程序(101fffff)
-------------------------------
标识符 {24f342ef-c536-11ed-ae87-bfc294c32d5b}
description EFI Network
固件应用程序(101fffff)
-------------------------------
标识符 {24f342f1-c536-11ed-ae87-bfc294c32d5b}
description EFI PXE 0 for IPv4 (E8-80-88-32-09-E5)
固件应用程序(101fffff)
-------------------------------
标识符 {6e9edf43-4038-11ef-b884-806e6f6e6963}
device partition=\Device\HarddiskVolume2
path \EFI\ubuntu\shimx64.efi
description ubuntu
固件应用程序(101fffff)
-------------------------------
标识符 {80c4fcf4-356d-11ef-b875-806e6f6e6963}
device partition=\Device\HarddiskVolume2
path \EFI\ubuntu\shimx64.efi
description EFI PXE 0 for IPv6 (E8-80-88-32-09-E5)
====
其中{bootmgr}是Windows，{6e9edf43-4038-11ef-b884-806e6f6e6963}是ubuntu。
displayorder {6e9edf43-4038-11ef-b884-806e6f6e6963} 意思是默认启动ubuntu。
如果需要将默认项改为windows：
bcdedit /set {fwbootmgr} displayorder {bootmgr} /addfirst
然后验证：
bcdedit /enum firmware
====
固件启动管理器
---------------------
标识符 {fwbootmgr}
displayorder {bootmgr}
{6e9edf43-4038-11ef-b884-806e6f6e6963}
{24f342ed-c536-11ed-ae87-bfc294c32d5b}
{24f342ee-c536-11ed-ae87-bfc294c32d5b}
{24f342ef-c536-11ed-ae87-bfc294c32d5b}
timeout 0
...
====
ubuntu:
sudo apt install efibootmgr
sudo efibootmgr -v
====
udo efibootmgr -v
BootCurrent: 0000
Timeout: 0 seconds
BootOrder: 0000,0004,2001,2002,2003
Boot0000* ubuntu HD(2,GPT,482a0972-8bb0-47e8-ad58-72544161a93e,0x8000,0x5f800)/File(\EFI\ubuntu\shimx64.efi)RC
Boot0002* EFI PXE 0 for IPv4 (E8-80-88-32-09-E5) PciRoot(0x0)/Pci(0x2,0x3)/Pci(0x0,0x0)/MAC(e880883209e5,0)/IPv4(0.0.0.00.0.0.0,0,0)RC
Boot0003* EFI PXE 0 for IPv6 (E8-80-88-32-09-E5) PciRoot(0x0)/Pci(0x2,0x3)/Pci(0x0,0x0)/MAC(e880883209e5,0)/IPv6([::]:<->[::]:,0,0)RC
Boot0004* Windows Boot Manager HD(1,GPT,a105c1d0-3330-48e1-8798-fbfec93dbc48,0x800,0x32000)/File(\EFI\Microsoft\Boot\bootmgfw.efi)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.e.a.8.6.2.c.-.5.c.d.d.-.4.e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}....................
Boot2001* EFI USB Device RC
Boot2002* EFI DVD/CDROM RC
Boot2003* EFI Network RC
====
复制BootOrder: 0000,0004,2001,2002,2003里面的全部内容，调整顺序，执行：
sudo efibootmgr -o 0004,0000,2001,2002,2003