A UEFI machine has two installed distributions. The firmware currently starts the older one first, and you want the newly installed entry to be tried first from now on, without touching the firmware setup screen. Which tool changes the boot order?
LPIC-1 Exam 101-500, objective 101. System architecture medium
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Correct efibootmgr
Correct. efibootmgr reads and writes the EFI boot variables, so `efibootmgr -v` lists the entries and `efibootmgr -o 0003,0001` sets the order in which the firmware tries them.
Not correct grub-install
Wrong for this task. grub-install writes the boot loader image to the EFI System Partition (and normally creates one boot variable for it), but it is not the tool for reordering entries that already exist.
Not correct update-grub
Wrong. update-grub regenerates GRUB's own menu, grub.cfg. That menu is only consulted after the firmware has already chosen which boot loader to start.
Not correct fdisk
Wrong. fdisk edits the partition table. It can show that the EFI System Partition exists, but it cannot influence which boot variable the firmware uses.
Why
UEFI firmware keeps its boot menu in NVRAM as a set of variables: BootXXXX entries, each naming a loader file on the EFI System Partition, plus BootOrder and BootCurrent. efibootmgr is the userspace front end to those variables through /sys/firmware/efi/efivars/, so -o sets the order, -c creates an entry, and -B deletes one. Keep the two menus apart: the firmware's boot order decides which loader runs, and GRUB's grub.cfg decides which kernel that loader offers. If /sys/firmware/efi is absent, the machine booted in legacy BIOS mode and efibootmgr has nothing to talk to.
Where this comes from
- Cited
- manual page efibootmgr(8)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 101 and space the ones you get wrong.
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