Linux Boot Process 2 — Questions and Answers
Question 1: Which systemd target is the equivalent of the traditional SysVinit runlevel 3?
- graphical.target
- multi-user.target (Correct answer)
- rescue.target
- network.target
Correct answer: multi-user.target
multi-user.target corresponds to runlevel 3 — multi-user, non-graphical mode.
Question 2: What is the purpose of the initramfs (initial RAM filesystem) during the Linux boot process?
- To store the bootloader configuration
- To provide a temporary root filesystem so the kernel can mount the real root (Correct answer)
- To load the BIOS firmware
- To initialize network interfaces before the kernel starts
Correct 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.
Question 3: Which command displays the systemd boot log from the current boot session?
- dmesg -b
- journalctl -b (Correct answer)
- systemctl log --boot
- bootlog --current
Correct answer: journalctl -b
journalctl -b shows log entries from the current boot; -b 0 is implicit for the latest boot.
Question 4: In GRUB2, which file is the primary human-editable configuration file on most Linux distributions?
- /boot/grub2/grub.cfg
- /etc/default/grub (Correct answer)
- /etc/grub2.conf
- /boot/grub/menu.lst
Correct answer: /etc/default/grub
/etc/default/grub holds user-editable settings; grub.cfg is auto-generated from it via grub2-mkconfig.
Question 5: What does the kernel parameter 'rd.break' do when added to the boot command line?
- Skips loading network drivers
- Drops to a shell just before the real root is switched to (Correct answer)
- Forces the kernel into single-user mode
- Disables SELinux enforcement during boot
Correct 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.
Question 6: Which systemd unit type is responsible for mounting filesystems during boot?
- .service
- .socket
- .mount (Correct answer)
- .path
Correct answer: .mount
.mount units correspond to filesystem mount points and are generated from /etc/fstab entries.
Question 7: What is the default behavior of GRUB2 when no kernel is selected during the timeout?
- It reboots the system
- It boots into rescue mode
- It boots the default (first highlighted) menu entry (Correct answer)
- It halts and waits indefinitely
Correct 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.
Linux Boot Process 2
Which systemd target is the equivalent of the traditional SysVinit runlevel 3?