efibootmgr: add page (#3788)

pages/linux/efibootbgr.md

@@ -0,0 +1,24 @@
+# efibootmgr
+
+> Manipulate the UEFI Boot Manager (the Bootoptions).
+> More information: https://linux.die.net/man/8/efibootmgr.
+
+- List the current settings / bootnums:
+
+`efibootmgr`
+
+- List the filepaths:
+
+`efibootmgr -v`
+
+- Add UEFI Shell v2 as a boot option:
+
+`sudo efibootmgr -c -d {{/dev/sda1}} -l {{\EFI\tools\Shell.efi}} -L "{{UEFI Shell}}"`
+
+- Change the current boot order:
+
+`sudo efibootmgr -o {{0002,0008,0001,0005}}`
+
+- Delete a boot option:
+
+`sudo efibootmgr -b {{0008}} --delete-bootnum`