Linux packages, dependencies and safe updates

What it means

A package transaction is the complete set of proposed changes, not just a new version label. Review it in two separate ways: what would change, and whether those changes fit your operational permission and recovery arrangements. A plan can contain the update you wanted and still fail that review because it also removes something outside the agreed scope.

Try it

Example: begin with Candidate transaction = web-only and Documented recovery path verified? = no. Change only Documented recovery path verified? to yes, then use Compare with baseline to inspect the two outcomes. This changes a local planning assertion; it does not verify a backup or authorize an installation.

STOP: recovery plan unknown. Approved fixture scope: update web-example only. Actual candidate: web-example: 2 → 3. The fixture does not establish how the prior working state would be restored. Inspect that evidence before an authorized change.

Keep Candidate transaction = web-only. The invented version change, web-example: 2 → 3, and the approved web-only scope remain fixed while you change the recovery assertion.

Reset restores Candidate transaction = web-only and Documented recovery path verified? = no, removes input errors, and clears the baseline comparison. It preserves your independent choices to open or close FAQ answers and About this model.

How it works

A requested version change is only the starting point. The package manager must account for dependency requirements and the versions available under the configured repositories and policies. Resolving those requirements can produce a broader transaction than the package name you entered. That complete proposal—not the presence of a newer version—is what you need to review. For a separate synthetic dependency example, suppose application A version 3 requires library B version 2 or later, but B version 1 is installed. Updating A alone would leave that requirement unmet: the proposed transaction must also satisfy B's requirement, or the update cannot proceed as proposed. This illustrates a version requirement, not the reason for the lab's invented database removal.

The local example begins after that resolution step: its two plans are already written. The web-only plan contains web-example: 2 → 3. The web-and-database-removal plan adds database-example: remove. The model does not calculate why a dependency would require the removal. It asks a narrower question: does the supplied plan fit the exercise's approved scope?

The decision has two gates. First, a database removal triggers STOP because only the web package update is authorized. If the plan stays within that scope, the model checks the recovery assertion. A no leaves recovery unknown; a yes makes the plan eligible for further review. Neither a technically plausible transaction nor a recovery assertion expands your permission to change the system.

Worked example

This is a synthetic baseline, not captured output from a machine.

The proposed change is web-example: 2 → 3, which fits the exercise's approved package scope. The intermediate condition is therefore not an unexpected package change: it is missing recovery evidence. That produces STOP: recovery plan unknown. Keeping these two checks separate explains why a small, in-scope transaction can still require you to stop.

What changes when the condition changes

Change Documented recovery path verified? from no to yes, keeping Candidate transaction = web-only. The result becomes Plan eligible for further review. Approved fixture scope: update web-example only. Actual candidate: web-example: 2 → 3. The supplied recovery assertion is not a verified restore or execution permission. A real plan and environment must be checked separately.

The package changes are identical to the baseline. Only the recovery assertion changed, so the example no longer reports missing recovery evidence. It has not established that an installation would succeed or that the service would work afterward.

Now keep recovery = yes and select web-and-database-removal. The result is STOP: unexpected removal. The candidate contains web-example: 2 → 3; database-example: remove. The removal exceeds the fixed web-only scope, so a positive recovery assertion cannot make the plan eligible. This scope check takes precedence even when recovery = no.

In practice

Use this as a preflight framework, not an installation command sequence. The command reference supplied here is Debian bookworm apt-get(8); do not assume its behavior or options apply unchanged to every Linux package manager or version.

1. Establish the environment and authority. Identify the distribution, installed package-manager version, configured repositories, affected service, and service owner. Confirm which account may inspect the relevant configuration and who is authorized to make changes. Missing access or uncertain authority is a reason to stop, not to escalate privileges experimentally.
2. Inspect before changing anything. Obtain the proposed transaction using the documented simulation mode for that environment. Read the complete list of proposed installations, upgrades, and removals. Record the exact permitted package set and justified dependency changes. In this exercise, the scope is only web-example: 2 → 3; database-example: remove is outside it. A real simulation does not lock future package or system state.
3. Resolve STOP conditions. Expect every proposed change to have an understood reason within the approved scope. Stop for an unexpected removal, an unexplained dependency change, unknown restart impact, or missing recovery evidence. Investigate the discrepancy before requesting a different scope; do not treat the desired update appearing in the plan as sufficient approval.
4. Prepare the before-state and recovery plan. Record the relevant installed versions, configuration, and expected service behavior. Establish a recovery procedure appropriate to the service and its data, including how you will verify that recovery worked. This page does not establish that reinstalling an older package would restore the prior working state. Without an established recovery route, do not proceed.
5. Keep execution separate from this example. Any real change needs an authorized, environment-specific procedure limited to the reviewed transaction. After that change, verify both the intended package state and the affected service's expected behavior. If either differs, stop further changes and follow the approved recovery procedure when indicated. After recovery, verify both layers again rather than assuming that the rollback action succeeded.

Limits and unknowns

The scene contains two invented transaction plans, not an APT output parser or a package-security check. It cannot tell you whether a real package set is resolvable, whether an update fixes a vulnerability, which services would restart, or whether recovery would work. No package installation, restart, or rollback is performed, and no real machine is inspected.

The unknown baseline means recovery evidence is missing; it is not a prediction that the update will fail. Likewise, Plan eligible for further review is not execution permission or a safety guarantee. The STOP rules express the exercise's declared operational scope and review policy, not rules enforced by APT.

Only the listed transaction choices and yes/no recovery values are supported. If an input is invalid, no calculated outcome applies until you correct it or use Reset; do not rely on an earlier valid result. Without JavaScript, the initial result and written examples remain readable, but the controls do not operate.

What to carry forward

Review the complete proposed transaction, not just the requested version change. A plan must stay within the authorized scope, have an established recovery path, and support checks of both package state and service behavior. If any of those conditions is unknown, your next step is to collect the missing evidence—not to approve the update.