On a UEFI machine you run grub-install without naming a disk device and the command succeeds. What has it done?
LPIC-1 Exam 101-500, objective 102. Linux installation and package management hard
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The options
Correct Written a GRUB EFI application into the EFI System Partition given by --efi-directory and registered a boot entry in the firmware's NVRAM.
Correct. UEFI booting is by file, not by boot sector, so grub-install installs an .efi binary under /EFI on the ESP and calls efibootmgr to add the variable that points at it.
Not correct Written the core image into the master boot record of the first disk it found.
Wrong. That is the BIOS installation path, which is exactly why it needs a device argument; UEFI firmware ignores the MBR boot code.
Not correct Generated /boot/grub/grub.cfg from /etc/default/grub and /etc/grub.d.
Wrong. Generating the configuration is the job of grub-mkconfig; grub-install installs the loader itself.
Not correct Created a BIOS boot partition on the disk holding /boot.
Wrong. A BIOS boot partition is only needed for legacy booting from a GPT disk, and grub-install never creates partitions.
Why
The two firmware models change what installation means. Under BIOS, grub-install takes a device and writes boot code into the MBR plus an embedded core image, so the target is a disk. Under UEFI it takes no device: the target is the mounted ESP, selected with --efi-directory, and the firmware finds the loader through an NVRAM boot variable or the fallback path /EFI/BOOT/BOOTX64.EFI. In both cases the menu itself still comes from grub.cfg.
Where this comes from
- Cited
- manual page grub-install(8)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 102 and space the ones you get wrong.
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