CV0-004 Troubleshooting Practice Question
Exhibit
Refer to the exhibit. [cloud-init] Error: Failed to mount /dev/xvdb1 on /mnt: No such device [cloud-init] Failed to mount /dev/xvdb1 on /mnt: No such device [cloud-init] Instance initialization failed: mountall
A cloud instance fails to initialize. The cloud-init log shows the error above. Which of the following is the most likely cause?
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
✓
The launch template specifies a block device mapping that is not attached to the instance.
The error 'No such device' indicates that the device specified in the block device mapping does not exist on the instance. Option D is correct because the launch template likely references a block device mapping for a device that is not actually attached (e.g., an ephemeral disk or misconfigured EBS volume). Option A is incorrect because an unformatted filesystem would produce a different error (e.g., 'mount: unknown filesystem type'). Option B is incorrect because if the disk were not attached at all, the device path would not appear in the system, but the error references a specific device path that is missing. Option C is incorrect because a corrupted partition table would yield errors like 'invalid partition table', not 'No such device'.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The filesystem on /dev/xvdb1 is not formatted with a recognized filesystem.
Why it's wrong here
Filesystem error would say 'wrong fs type'.
- ✗
The disk is not attached to the instance at all.
Why it's wrong here
If not attached, the device node would not appear.
- ✗
The partition table on /dev/xvdb1 is corrupted.
Why it's wrong here
Corruption gives partition read errors, not 'no such device'.
- ✓
The launch template specifies a block device mapping that is not attached to the instance.
Why this is correct
The device /dev/xvdb1 is present in the mapping but not attached, causing mount failure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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