You replaced the boot disk in a BIOS/MBR system and need to write the GRUB 2 boot loader into the master boot record of /dev/sda, installing the required GRUB modules under /boot. Which command does that?
LPIC-1 Exam 101-500, objective 102. Linux installation and package management medium
Machine-checked — no person has signed for it. This question was read against the source cited below by an automated pass, which found no contradiction. That is a weaker claim than it sounds: the same kind of process wrote the question, so it can confirm its own mistake.
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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
Not correct grub-mkconfig -o /boot/grub/grub.cfg
Wrong. This only regenerates the menu configuration file. It writes nothing to the disk's boot sector, so a disk with no boot loader stays unbootable.
Correct grub-install /dev/sda
Correct. grub-install writes the boot image to the target device's boot sector and copies the GRUB modules and core image into /boot/grub.
Not correct grub-mkrescue -o /dev/sda
Wrong. grub-mkrescue builds a bootable rescue ISO image; -o names an image file to create, not the system disk to install onto.
Not correct update-grub /dev/sda
Wrong. update-grub is a Debian/Ubuntu wrapper that just runs 'grub-mkconfig -o /boot/grub/grub.cfg' to rewrite the menu file. It writes no boot loader to any device, and a device argument is not valid for it.
Why
Keep the two GRUB 2 halves apart. grub-install puts the boot loader itself onto a device (MBR or the EFI system partition). grub-mkconfig, and its Debian wrapper update-grub, only rebuild the menu file grub.cfg. Installing a new disk needs the first; adding a kernel needs the second.
Where this comes from
- Cited
- LPI exam objective 102.2
- What it says
- Install and configure a boot loader such as GRUB 2, including interacting with the boot loader.
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.
More questions on this objective
- A mail server keeps filling its root filesystem because spooled mail and logs grow without bound, and when the disk fills the whole system becomes unusable. Which single change to the disk layout most directly contains that failure? machine-checked
- In LVM terminology, which object is created directly on a partition or whole disk so that its storage can be added to a pool? machine-checked
- You are laying out storage for a general-purpose Linux server. Which TWO of the following are genuine reasons to use LVM for the data filesystems rather than plain partitions? machine-checked
- Which file is the configuration file that GRUB 2 generates, and which administrators are told not to edit by hand on a typical Linux distribution? machine-checked
- On a GRUB 2 system whose configuration file is /boot/grub/grub.cfg, type the grub-mkconfig command — including the option and its argument — that regenerates that file. machine-checked
- A GRUB menu entry ends with the directives 'set root=(hd0,3)' followed by 'chainloader +1'. What is GRUB doing? machine-checked