Files
felhom.eu/documentation
admin e70b5feebe docs(R-117): the hang case measured — an I/O probe turns a wedged drive into an unkillable agent
Completes the spike once the venue came back. Q4's hang case and teardown are
now measurements, not plans.

Against a dmsetup-suspended device (I/O queues instead of returning EIO):

- P1 (devno compare) and P2 (ext4 abort flags) completed in 364us / 206us.
  They read /proc, so no block device is involved.
- statfs and getdents completed and reported HEALTHY — on a wedged device they
  do not even hang. R-117b confirmed in a second failure mode.
- EVERY probe that touches the device blocked, including a buffered write with
  no fsync: the O_CREAT metadata path needs journal access
  (wchan=do_get_write_access). There is no cheap-and-safe write probe.
- The blocked process survived SIGTERM AND SIGKILL (stat=D,
  wchan=folio_wait_bit_common, still alive 3m50s after kill -9) and died only
  when the device was resumed. So `systemctl restart felhom-agent` would hang,
  leaving the agent unrecoverable until the device returns or the host reboots.
  The thread count does not reveal the leak (5->5, 5->6).

Filed as R-117f. A timeout protects the caller's control flow and nothing else,
so "the fix must issue no block I/O" is now a fence rather than a preference —
the thread-leak hypothesis the probes were built to test turned out to be the
weaker half of the result.

Teardown done, all three layers: guest 9301 destroyed, r117scratch removed, both
dm and both loop devices gone, scsi_debug unloaded, local back to 37.02% against
a 37.00% session start. Fences re-verified AFTER teardown: 9201 running,
drill-r50 stopped, local-lvm 38.84% byte-identical, felhom-backup content
unchanged, live /mnt/felhom-drives intact with both submounts, agent active.
Layer 3 genuinely empty — 9301 had no NIC and ran no controller.

Trap recorded: a suspended dm device must be resumed BEFORE any umount, or the
teardown blocks on the same uninterruptible sleep.
2026-07-30 11:49:59 +02:00
..

Felhom — Documentation

Felhom is a managed home-server service for Hungarian households, built on a three-component model over Proxmox:

  • Hub — operator backend on k3s (hub.felhom.eu). Repo: felhom.eu/hub/.
  • Host agent — one per Proxmox host; operator-tier; owns all Proxmox interaction. Repo: felhom-agent/.
  • In-guest controller — one per customer LXC; Docker-only; manages the customer's apps. Repo: felhom-controller/.

This directory is the central, code-verified documentation home for all three components plus the platform and the security-audit record.

Sections

Controller (in-guest) — controller/

The Docker-only app-domain controller. Full per-area docs grounded in current source (v0.59.0). → controller/README.md: module map, deploy & stack lifecycle, backup architecture, storage/monitoring/metrics, auth/hub/sync/integrations.

Host agent & platform — architecture/, proxmox-platform.md

The operator-tier agent and the Proxmox platform.

Hub (operator backend) — architecture/05

Security audits & remediation — audits/

Spike & test findings — tests/

Per-slice spike/validation findings (phases 05, slices 710). See tests/.

Conventions

  • Code-verified, not memory-derived. Architectural claims here are checked against the actual current source; if a claim can't be verified it is omitted and flagged, not guessed.
  • Per-repo operational working files (CLAUDE.md, CONTEXT.md, CHANGELOG.md, BUGHUNT.md, REPORT.md, TASK.md) live in their own repos — they are operational, not published docs.
  • Authoritative versions at last refresh: controller v0.59.0, agent v0.29.1, hub v0.11.0.