Chapter 11 — Inventory in practice
Lesson map
Lesson 11 published. Map, example, EX031.
flowchart TD
N0["Learning outcomes"]
N1["11.1 Sources"]
N2["11.2 Reconciling"]
N3["11.3 Fields that matter"]
N4["11.4 Keeping it current"]
N5["Disposal"]
N6["Classroom devices"]
N7["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> N6 --> N7
N7 --> EX["Worked example"]
EX --> Q["Exercise EX031"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["11.1 Sources"]
N2["11.2 Reconciling"]
N3["11.3 Fields that matter"]
N4["11.4 Keeping it current"]
N5["Disposal"]
N6["Classroom devices"]
N7["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> N6 --> N7 --> Q["EX031"]
[Learning outcomes]
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[11.1 Sources]
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[11.2 Reconciling]
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[11.3 Fields that matter]
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v
[11.4 Keeping it current]
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v
[Disposal]
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v
[Classroom devices]
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v
[Synthesis]
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[Worked example] --> [Exercise EX031]
Learning outcomes
You will (1) build an asset list from several sources; (2) reconcile differences; (3) keep it current.
11.1 Sources
Tomás gathers the directory's computer list, the management service's device list and the purchasing records. Each is incomplete: the directory includes old computers never removed, the management service misses some classroom laptops, and purchasing lacks donated devices.
Tomás exports all three in the same week so that differences come from the sources rather than from time passing between exports. He also notes what each source is for: the directory controls sign-in, the management service applies settings, and purchasing records what the trust paid for. None of the three sources was ever designed to be a complete inventory.
11.2 Reconciling
He matches by serial number and lists differences. Twelve directory entries are for machines long gone; four laptops are in use but not managed; two donated laptops appear nowhere. Each difference is resolved with Dev: stale entries removed, unmanaged laptops enrolled, donated laptops recorded.
Serial numbers are used because hostnames change when a laptop is rebuilt or passed to a new teacher, while the serial stays with the hardware. Where a source has no serial for a device, Tomás matches it by hostname and last sign-in date instead, and marks it as a weaker match for Dev to confirm.
11.3 Fields that matter
For each device: owner or location, operating system and version, last check-in, encryption state and support end date. These fields support the later chapters on patching, encryption and replacement.
Owner or location says who to ask when something is wrong, which is exactly the field missing for the classroom tablets. Last check-in shows whether a device is still in use and reporting, and support end date drives the replacement plan. Encryption state is kept here as well as in the console, so the inventory alone can answer a data protection question about a lost laptop.
11.4 Keeping it current
A monthly comparison, run by a script, flags new differences. Leavers' laptops are returned and recorded through the same form as account disabling.
The script compares the three exports by serial and prints only the differences, so a month with no changes produces a one-line result. Each difference is resolved the same way as during reconciliation: removed, enrolled or recorded. Dev keeps the monthly outputs in a dated folder, which later shows whether the inventory stayed accurate after the placement ended.
Disposal
An inventory also tracks devices leaving. Old laptops are wiped with the vendor's secure erase for solid-state drives, and the serial is marked as disposed with a certificate from the recycling company. NIST SP 800-88 gives guidance on media sanitisation; Tomás reads its summary to understand why simple deletion is not enough.
The twelve stale directory entries turn out to include four laptops that were recycled without records. Dev contacts the recycler and obtains certificates for three; the fourth is recorded as unknown and reported to the data protection officer.
Classroom devices
The classroom tablets were the one group nobody clearly owned, which is why they were missing from every list. Unowned devices drift: nobody checks their updates, nobody notices when one disappears and nobody removes them when they break. Tomás proposes that each school's computing lead owns its tablets. Each term the lead confirms the count against the management service, reports any lost or broken tablets to Dev and checks that the tablets still receive updates. Ownership does not mean the computing lead does technical work; it means one person notices and asks. The first termly count finds two tablets missing, later found in a storeroom.
Worked example
The reconciled list contains 94 laptops and 6 servers; four unmanaged laptops are enrolled within a week.
Synthetic case. Figures are synthetic.
Errors and limits
An inventory that is not maintained becomes wrong within months.
Exercises
- EX031 — Source weaknesses. Give one weakness of each of the three inventory sources. Rubric: 3 = three correct;; 2 = two;; 1 = one;; 0 = none.
- EX032 — Matching key. What key should match records across sources? Rubric: 3 = serial with reason;; 2 = serial;; 1 = hostname;; 0 = none.
- EX033 — Monthly check. Describe what the monthly script compares. Rubric: 3 = management list against directory and purchasing, reporting differences;; 2 = lists;; 1 = vague;; 0 = none.
Synthesis
Reconciling sources produces an inventory that later checks can trust.
Continue studying — chapter 11 of 30
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