XK0-006 Troubleshooting Practice Question
An administrator needs to check the kernel ring buffer for hardware error messages after a system crash. Which command should be used?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
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dmesg
dmesg shows kernel ring buffer messages including hardware errors. journalctl -k shows kernel messages from systemd journal, but dmesg is the direct command for the ring buffer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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dmesg
Why this is correct
dmesg reads the kernel ring buffer, which retains hardware detection, driver and error messages logged by the kernel. After a crash, this buffer holds the relevant hardware diagnostics, satisfying the requirement to inspect kernel-level error output.
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journalctl -k
Why it's wrong here
journalctl -k reads the kernel log only if the systemd journal persists kernel messages; after a crash, dmesg or the saved /var/log/kern.log may hold the hardware errors, and journalctl -k can return nothing if journald storage is volatile. It is tempting because it queries kernel messages, and would be correct on a system with persistent journald storage.
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tail -f /var/log/messages
Why it's wrong here
tail -f /var/log/messages follows a userspace syslog file, which may not exist on systemd distributions and does not reliably capture kernel ring buffer entries. It is tempting because tailing logs suits live monitoring of application or service messages, but hardware errors land in the kernel log, read via dmesg or journalctl -k.
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strace -e trace=open
Why it's wrong here
strace traces a process's system calls, so it cannot read kernel messages. The ring buffer is exposed via dmesg, which prints the kernel log directly. strace would be the right tool for diagnosing which files a failing program opens, not for post-crash hardware diagnostics.
Go deeper
Related to this question
Key term
Kernel
The kernel is the core program of an operating system that manages hardware resources and provides essential services for all other software to run.
Key term
systemd
systemd is a system and service manager for Linux operating systems that initializes and manages processes, services, and system resources after the kernel boots.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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