XK0-006 Troubleshooting Practice Question
A Linux administrator notices that a server's clock is drifting and NTP synchronization is failing. The administrator runs 'chronyc sources' and sees that all sources are marked with a '?' character. Which command should be run next to diagnose why chronyd cannot reach the NTP servers?
⚠ Common exam trap
A common mix-up: candidates confuse the '?' state with a simple lack of synchronization, when it actually indicates the source is unreachable and requires packet-level diagnosis.
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
✓
chronyc ntpdata
The '?' character in chronyc sources means the source is unreachable or has not provided a valid packet. To diagnose why, chronyc ntpdata shows per-source packet details, including whether NTP requests are being sent and responses received. This helps identify network blocks, incorrect server addresses, or firewall rules. Other chronyc subcommands like tracking, activity, and sourcestats do not provide the packet-level view needed for this specific failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
chronyc ntpdata
Why this is correct
chronyc ntpdata displays detailed NTP packet information for each configured source, including the source address, mode, stratum, and whether packets are being received. When a source shows '?', it indicates that no valid packets have been received recently. ntpdata will reveal if packets are being sent but not returned, or if there are errors, helping diagnose firewall, routing, or server issues.
- ✗
chronyc tracking
Why it's wrong here
chronyc tracking shows the current time offset, frequency, and reference ID of the system clock relative to the selected source. It does not show why sources are unreachable; it only reports the state of the local clock. If no source is selected, tracking will show a reference ID of 00000000, but it will not explain the network or configuration issue causing the '?' state.
- ✗
chronyc activity
Why it's wrong here
chronyc activity displays the number of servers and peers that are online or offline, but it does not provide details about why a specific source is unreachable. It gives a high-level count, not per-source diagnostics. To understand the '?' state, you need to see the source's reachability and last packet information, which activity does not show.
- ✗
chronyc sourcestats
Why it's wrong here
chronyc sourcestats shows statistics for each source, such as offset, frequency, and skew, but only for sources that have been reachable. If a source is marked '?', it means no valid packets have been received, so sourcestats will not have data for it. This command is useful for analyzing a source that is already working, not for diagnosing an unreachable one.
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Related to this question
Learn chapter
Installing Linux and Package Management
Key term
NTP
Network Time Protocol is a networking protocol used to synchronize the clocks of computers and devices over a network to a common time reference.
Key term
Linux
Linux is an open-source operating system that manages computer hardware and software, widely used in servers, desktops, and embedded systems.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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