The W series has covered what to check before a major upgrade, when to apply it, and what can go wrong. This fourth part covers the remaining question: how to actually run it. Once the preparation is in place and the timing is right, this is the command sequence to follow — one stage at a time, with a confirmation step at each boundary.
Why not use the admin dashboard Update button
The WordPress admin screen has an "Update All" button that runs core, plugin, and theme updates in a single operation. This is the approach to avoid for major upgrades.
The reason is loss of isolation. When core plus five plugins plus two themes update in one pass, any breakage afterward has multiple suspects and no clear way to narrow them down. The dashboard update also displays "Updated successfully" even when PHP warnings or non-fatal errors occurred during the process — making it easy to miss problems until they surface later.
WP-CLI lets you apply core, the DB migration, plugins (one at a time), and themes in separate steps, with a check between each one.
