fix(packaging): let the service user read its own config - #11
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`systemctl start labelfab-agent` fails on any fresh install:
PermissionError: [Errno 13] Permission denied: '/etc/labelfab/agent.toml'
postinst did `chmod 750 /etc/labelfab` but never chowned it, so the directory
stayed root:root. The unit runs as User=labelfab, which therefore could not even
traverse it. The package has been unusable out of the box since the unit gained
User=labelfab; the only reason it was not obvious is that postinst deliberately
enables without starting, so the failure waits until an operator finishes setup and
looks like their misconfiguration rather than ours.
Now root-owned and group-readable: the agent can read its config, only root can
write it. The config file itself was also shipping 0664 -- world-readable, which it
has no reason to be even with the password held outside it -- so it is 0640 now.
Demonstrated in a clean bookworm container, installing each .deb and su'ing to the
service user:
0.2.0 /etc/labelfab root:root read: NO -> PermissionError
0.2.1 /etc/labelfab root:labelfab read: YES -> config loads
The chown of agent.toml is guarded by a -f test because postinst also runs on
upgrade, where a purged-config box would otherwise fail the script under `set -e`.
impuls42
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Jul 30, 2026
Fresh installs could not start: postinst left /etc/labelfab root-owned so the labelfab service user could not read its own config (#11).
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The bug
systemctl start labelfab-agentfails on any fresh install:postinst.shdoeschmod 750 /etc/labelfabbut never chowns it, so it staysroot:root. The unit runs asUser=labelfab, which cannot even traverse the directory — let alone read the config.Found by installing 0.2.0 from apt-tap onto the workshop box and starting the service for the first time.
The package has been unusable out of the box since the unit gained
User=labelfab. It stayed hidden becausepostinstdeliberately enables-but-does-not-start, so the failure surfaces later, during operator setup, where it reads like their misconfiguration rather than ours.Verification
Both
.debs built from this tree and installed in a cleandebian:bookworm, thensu'd to the service user:/etc/labelfabdrwxr-x--- root rootPermissionErrordrwxr-x--- root labelfabChange
Root-owned, group-readable: the agent can read its config, only root can write it.
agent.tomlwas also shipping0664— world-readable. It has no reason to be, even with the MQTT password deliberately held outside it, so it is0640now.The
chownofagent.tomlis guarded by a-ftest:postinstalso runs on upgrade, and on a box whose config had been purged the unguarded form would abort the script underset -e.