scripts/assert-uid-free.sh is the verification half of docs/deprovision-os-account.md, written
outside the implementation on purpose: a checker the function calls is a restatement of its own
beliefs rather than an audit. Nine checks — passwd entry, uid reuse, both subid files, linger,
runtime dir, live processes, files owned by the uid, and files owned anywhere in the freed
subuid range.
Two modes, because the range has to be captured BEFORE deletion. userdel removes the
/etc/subuid entry along with the account, and after that there is no way to ask what range it
held — so a checker that only runs afterwards silently drops the half most likely to be wrong.
Exercised against green while fully provisioned: eight of nine checks fail, exit 1. A checker
that has never been seen to fail is not evidence.
And the trap worth knowing before anyone trusts a green result: the subuid check passes
vacuously on most accounts. Files get a mapped owner only when a process inside a container runs
as a NON-root user; an image whose files are root-owned maps to the member's own uid and leaves
the range empty. Measured on green after a night of real use — claude installed, an image
pulled, transcripts written — the range check found zero files and passed without testing
anything. The spec now says how to build a specimen that actually exercises it, and to watch the
check fail on that tree before trusting it to pass on a cleaned one.
Docs and a script only; no behaviour change. On a branch, for whoever merges it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
