Exercise 1: Why No Disk-Space Alert Fired — Possible Solution
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CloudWatch automatically collects only metrics visible from OUTSIDE
an EC2 instance -- CPU utilization, network traffic, and disk I/O
(read/write activity) -- with no setup required. Disk SPACE
utilization (how full the disk actually is) is a genuinely different
kind of metric: it requires visibility from INSIDE the instance's own
operating system, which CloudWatch cannot see by default.

Because no disk-space metric was ever actually being collected in the
first place, there was nothing for an alarm to watch, and therefore
nothing that could ever trigger -- not because the alarm was
misconfigured, but because the underlying metric it would need to
watch was never being reported to CloudWatch at all.

ANSWER: This happened because CloudWatch does not report disk-space
utilization automatically -- that requires installing the CloudWatch
Agent inside the instance itself. The missing step was installing and
configuring the CloudWatch Agent; without it, disk-space usage was
never a real metric CloudWatch had access to, so no alarm could ever
have been set up to watch it correctly.

WHY THIS WORKS AS AN ANSWER
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This correctly identifies the real root cause as a genuinely missing
metric, not a misconfigured alarm -- directly matching the chapter's
own warn-box about this specific, common real gotcha (teams assuming
CloudWatch monitors "everything" by default when memory and disk
space are real, documented exceptions).