XK0-005 Question #455: Real Exam Question with Answer & Explanation

Question

A Linux system is failing to start due to issues with several critical system processes. Which of the following options can be used to boot the system into the single user mode? (Choose two.)

Options

• AExecute the following command from the GRUB rescue shell: mount -o remount, ro/sysroot.
• BInterrupt the boot process in the GRUB menu and add systemd.unit=single in the kernel line.
• CInterrupt the boot process in the GRUB menu and add systemd.unit=rescue.target in the kernel
• DInterrupt the boot process in the GRUB menu and add single=user in the kernel line.
• EInterrupt the boot process in the GRUB menu and add init=/bin/bash in the kernel line.
• FInterrupt the boot process in the GRUB menu and add systemd.unit=single.target in the kernel

Explanation

To boot a Linux system into single-user mode (rescue mode) for troubleshooting, an administrator can modify the GRUB kernel line to specify systemd.unit=rescue.target or systemd.unit=single.target.

Common mistakes.

• A. The command mount -o remount, ro/sysroot is used to remount a filesystem read-only within a rescue environment, not to initiate single-user mode.
• B. systemd.unit=single is not a standard systemd unit target for single-user mode; the correct targets are single.target or rescue.target.
• D. single=user is not a valid kernel parameter for booting into single-user mode in modern systemd-based Linux distributions.
• E. While init=/bin/bash can launch a root shell, it bypasses the entire systemd initialization process, which is generally a less controlled and recommended method for recovery compared to using systemd targets.

Concept tested. Linux boot process and recovery modes (GRUB, systemd targets)

Reference. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_basic_system_settings/accessing-rescue-mode-and-emergency-mode_managing-basic-system-settings

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