Before using an Ubuntu ISO, distinguish two checks: whether the downloaded file matches the expected data, and whether the checksum list is authentic. Ubuntu documents verification of the signed list and comparison of the ISO checksum. The relevant files are SHA256SUMS and SHA256SUMS.gpg for the release you selected.

Prepare a clear working folder

Our suggested workflow starts with a separate folder for one release and one image. Keep a note of where you obtained each file. This makes it easier to avoid comparing a newly downloaded ISO with a list left over from another attempt.

Open the official verification guide and follow its complete sequence, including the signing-key checks. Do not substitute an abbreviated command copied from an unrelated discussion. The exact filenames and the result you are checking should correspond to the files in your folder.

Decide what counts as success

We recommend recording the outcome of each step separately instead of writing only “verified.” Note which image was checked and retain enough information to repeat the process. If a step fails, keep its message and resolve that step before proceeding to installation.

A useful handover to another person contains the chosen release, the image filename and the verification results. Avoid describing an incomplete check as successful simply because the download finished. This guide is a preparation checklist; it does not certify an image we have not inspected or announce a new Ubuntu release.