A hash turns a whole file into one short line. Hash it when you trust it, hash it again later, and the two lines tell you whether anything changed. This set covers what a digest depends on, how a check works, and what a FAILED line does and does not prove.
Each one is marked as you go, and the explanation arrives straight after, which is
the part worth reading.
4 questions, marked as you go.
Tasks
These need your own device. Run the command in Termux, then paste what it printed.
The marking looks at what the output means, so spacing, version numbers and
ordering do not matter. If you have not installed anything yet, the
lesson covers the setup.
Make a manifest and check it
This makes two small files, builds a manifest of their hashes with find and sha256sum, then checks the manifest straight back. Watch the two halves: the digests first, then the OK lines.
Run this in Termux
On your own device. Nothing on this page executes it. The command runs in
your terminal, and this box only reads what you paste back.
The manifest is the list of digests. The check reads that list and re-hashes each file, so the OK lines are the second half of the same run.
the manifest holds a hash for each watched file
the check reports every file as OK
the manifest and the check are both shown
the commands actually ran
What a good answer looks like
Two halves. The first half is the manifest: one line per file, each a 64-character digest, two spaces, then the path, sorted by path so it stays stable. The second half is the check, one line per file ending in OK, because nothing has changed yet. Change a file and its line would read FAILED instead, which is the whole point of keeping the manifest. If no OK line appears, sha256sum -c could not read the manifest.
Marking your own work
Both halves of this are checked in your browser, with no server involved, so nothing
stops you from pasting output you did not run. The tasks are written so that the
easiest way to pass one is to actually do it and read the result, which is the whole
intention.