Exercise 3: The Full Diagnostic Workflow for a Boot That Slowed Down Over a Week — Possible Solution
====================================================================

1. Run systemd-analyze to confirm the boot is genuinely slower than
   before, and get an overall breakdown (kernel/initrd/userspace time)
   -- confirming this really is a userspace/systemd-level slowdown
   worth investigating further, per the chapter's own first diagnostic
   step.

2. Run systemd-analyze critical-chain, NOT just blame, to find the
   actual dependency chain responsible for the total boot time -- per
   the chapter's own central distinction, blame alone could easily
   point at a unit that's slow but irrelevant to overall boot time, so
   critical-chain is the tool that actually identifies the real
   bottleneck.

3. From critical-chain's own output, identify the specific unit (or
   units) on that chain whose duration has genuinely grown -- this is
   the concrete unit responsible for the slowdown, not just "some slow
   unit" from blame's own list.

4. Run journalctl -u THATUNIT -b (systemd1-6's own tool) to
   investigate what that specific unit was actually doing during
   startup -- looking specifically for anything that might explain WHY
   it's gotten slower over the past week (a new dependency, a config
   change, a growing dataset it loads, etc.), since the slowdown
   developed gradually rather than appearing all at once.

5. Based on what's found: if the unit turns out not to be genuinely
   needed at boot time at all, systemctl disable it so it no longer
   delays the critical path; if it's actively causing harm and needs
   to be completely prevented from starting while further
   investigation continues, systemctl mask it instead -- but only
   after checking systemctl list-dependencies --reverse on it first
   (per the chapter's own warn-box), to confirm nothing else on the
   system genuinely depends on it before masking.

WHY THIS WORKS AS AN ANSWER
------------------------------
This reproduces the chapter's own full numbered workflow in the
correct order, correctly substituting critical-chain (not blame) as
the tool that actually identifies the bottleneck, and includes the
warn-box's own dependency check before the final masking step rather
than treating masking as an unconditional first response.