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This is efibootmgr, a Linux user-space application to modify the Intel Extensible Firmware Interface (EFI) Boot Manager. This application can create and destroy boot entries, change the boot order, change the next running boot option, and more.

Details on the EFI Boot Manager are available from the EFI Specification, v1.02 or above, available from http://developer.intel.com.

Note: efibootmgr requires that the kernel module efivars be loaded prior to use. 'modprobe efivars' should do the trick.

usage: efibootmgr [options]

1. a | –active sets bootnum active
2. A | –inactive sets bootnum inactive
3. b | –bootnum XXXX modify BootXXXX (hex)
4. B | –delete-bootnum delete bootnum (hex)
5. c | –create create new variable bootnum and add to bootorder
6. d | –disk disk (defaults to /dev/sda) containing loader
7. e | –edd [1|3|-1] force EDD 1.0 or 3.0 creation variables, or guess
8. E | –device num EDD 1.0 device number (defaults to 0x80)
9. g | –gpt force disk w/ invalid PMBR to be treated as GPT
10. H | –acpi_hid XXXX set the ACPI HID (used with -i)
11. i | –iface name create a netboot entry for the named interface
12. l | –loader name (defaults to \elilo.efi)
13. L | –label label Boot manager display label (defaults to “Linux”)
14. n | –bootnext XXXX set BootNext to XXXX (hex)
15. N | –delete-bootnext delete BootNext
16. o | –bootorder XXXX,YYYY,ZZZZ,… explicitly set BootOrder (hex)
17. O | –delete-bootorder delete BootOrder
18. p | –part part (defaults to 1) containing loader
19. q | –quiet be quiet
20. -test filename don't write to NVRAM, write to filename
21. t | –timeout seconds Boot manager timeout
22. T | –delete-timeout delete Timeout value
23. u | –unicode | –UCS-2 pass extra args as UCS-2 (default is ASCII)
24. U | –acpi_uid XXXX set the ACPI UID (used with -i)
25. v | –verbose print additional information
26. V | –version return version and exit
27. w | –write-signature write unique sig to MBR if needed

Typical usage: 1) Root can use it to display the current Boot Manager settings.

[root@localhost ~]# efibootmgr
BootCurrent: 0004
BootNext: 0003
BootOrder: 0004,0000,0001,0002,0003
Timeout: 30 seconds
Boot0000* Diskette Drive(device:0)
Boot0001* CD-ROM Drive(device:FF) 
Boot0002* Hard Drive(Device:80)/HD(Part1,Sig00112233)   
Boot0003* PXE Boot: MAC(00D0B7C15D91)               
Boot0004* Linux

This shows:
BootCurrent - the boot entry used to start the currently running
system.

BootOrder - the boot order as would appear in the boot manager.  The
boot manager tries to boot the first active entry on this list.  If
unsuccessful, it tries the next entry, and so on.

BootNext - the boot entry which is scheduled to be run on next boot.
This superceeds BootOrder for one boot only, and is deleted by the
boot manager after first use.  This allows you to change the next boot
behavior without changing BootOrder.

Timeout - the time in seconds between when the boot manager appears
on the screen until when it automatically chooses the startup value
from BootNext or BootOrder.

Five boot entries (0000 - 0004), the active/inactive flag (* means
active), and the name displayed on the screen.

2) An OS installer would call 'efibootmgr -c'. This assumes that

 /boot/efi is your EFI System Partition, and is mounted at /dev/sda1.
 This creates a new boot option, called "Linux", and puts it at the top
 of the boot order list.  Options may be passed to modify the
 default behavior.  The default OS Loader is elilo.efi.

3) A system administrator wants to change the boot order. She would

 call 'efibootmgr -o 3,4' to specify PXE boot first, then Linux
 boot.

4) A system administrator wants to change the boot order for the next

 boot only.  She would call 'efibootmgr -n 4' to specify that the
 Linux entry be taken on next boot.

5) A system administrator wants to delete the Linux boot option from

 the menu.  'efibootmgr -b 4 -B' deletes entry 4 and removes it
 from BootOrder.

6) A system administrator wants to create a boot option to network

 boot (PXE).  Unfortunately, this requires knowing a little more
 information about your system than can be easily found by
 efibootmgr, so you've got to pass additional information - the ACPI
 HID and UID values.  These can generally be found by using the EFI
 Boot Manager (in the EFI environment) to create a network boot
 entry, then using efibootmgr to print it verbosely.  Here's one example:

   Boot003* Acpi(PNP0A03,0)/PCI(5|0)/Mac(00D0B7F9F510) \
ACPI(a0341d0,0)PCI(0,5)MAC(00d0b7f9f510,0)

 In this case, the ACPI HID is "0A0341d0" and the UID is "0".
 For the zx2000 gigE, the HID is "222F" and the UID is "500".
 For the rx2000 gigE, the HID is "0002" and the UID is "100".
 You create the boot entry with:
 'efibootmgr -c -i eth0 -H 222F -U 500 -L netboot'

Many other uses may be found.