Both apps ran `chmod -R 777` over their data dirs in install_post_start —
after the container has booted and written files as its own uid (grafana
472 -> host subuid 231543, prometheus nobody 65534 -> 296605). chmod by a
non-owner fails, so every REINSTALL printed "Operation not permitted" per
file and failed the step; a fresh install passed only because the dir was
still empty when it ran. Reproduced on a live install of both.
The permission is only needed on the DIRECTORY, so the container can
create its store on first boot. What it creates after that is its own and
must stay that way — chowning or chmod'ing it away is what would actually
break these apps. So: non-recursive 0777 on grafana_storage and prom_data.
prometheus's config dir is a separate case — the container only READS it —
so it gets a+rX,go-w instead. The go-w matters: a+rX only adds bits, so
without it prometheus.yml stays world-writable on every install the old
777 already touched, and prometheus obeys that file. Everything there is
written through runFileOp, i.e. by the owner, so owner-write is enough.
updateFileOwnership used `runSystem chown`, but the scoped sudoers grants
the manager root only for the fixed LibrePortal helpers and
systemctl/ufw/nft/sysctl — never a bare chown, which would be
root-equivalent. It was denied on every call ("I'm sorry libreportal"),
printing a red ✗ Error on every prometheus install, and its message
referenced an undefined $user_name so it read "with ownership". Use
runFileOp (runs as the owner of the data plane) and name the user.
Verified live: prometheus and grafana both installed fresh and reinstalled
with 0 errors; prometheus.yml went 0777 -> 0755 with prometheus still
healthy (200); grafana serving 200; grafana.db and prom_data/data keep
their container uids.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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