XK0-005 · Question #455
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.)
The correct answer is C. Interrupt the boot process in the GRUB menu and add systemd.unit=rescue.target in the kernel F. Interrupt the boot process in the GRUB menu and add systemd.unit=single.target in the kernel. 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.
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
How the community answered
(35 responses)- A3% (1)
- C91% (32)
- D6% (2)
Why each option
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`.
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.
`systemd.unit=single` is not a standard systemd unit target for single-user mode; the correct targets are `single.target` or `rescue.target`.
Adding `systemd.unit=rescue.target` to the kernel boot parameters in the GRUB menu instructs systemd to boot into rescue mode, which provides a minimal environment and a root shell for system recovery and troubleshooting.
`single=user` is not a valid kernel parameter for booting into single-user mode in modern systemd-based Linux distributions.
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.
Similarly, adding `systemd.unit=single.target` to the kernel boot parameters in GRUB also achieves single-user mode, providing a minimal system environment with a root shell, often synonymous with rescue mode for system maintenance.
Concept tested: Linux boot process and recovery modes (GRUB, systemd targets)
Source: 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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