Boot Process Flashcards

Which systemd target is the equivalent of the traditional SysVinit runlevel 3?

Answer: multi-user.target

multi-user.target corresponds to runlevel 3 — multi-user, non-graphical mode.

What is the purpose of the initramfs (initial RAM filesystem) during the Linux boot process?

Answer: To provide a temporary root filesystem so the kernel can mount the real root

initramfs provides a temporary root filesystem in RAM that contains tools needed to mount the actual root filesystem.

Which command displays the systemd boot log from the current boot session?

Answer: journalctl -b

journalctl -b shows log entries from the current boot; -b 0 is implicit for the latest boot.

In GRUB2, which file is the primary human-editable configuration file on most Linux distributions?

Answer: /etc/default/grub

/etc/default/grub holds user-editable settings; grub.cfg is auto-generated from it via grub2-mkconfig.

What does the kernel parameter 'rd.break' do when added to the boot command line?

Answer: Drops to a shell just before the real root is switched to

rd.break breaks into a dracut/initramfs shell just before the switch_root call, useful for emergency root password recovery.

Which systemd unit type is responsible for mounting filesystems during boot?

Answer: .mount

.mount units correspond to filesystem mount points and are generated from /etc/fstab entries.

What is the default behavior of GRUB2 when no kernel is selected during the timeout?

Answer: It boots the default (first highlighted) menu entry

GRUB2 automatically boots the default entry once the timeout expires, which is typically the first or most recent kernel.