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Defender for Linux
I'll search for this — Microsoft publishes the Defender for Endpoint on Linux changelog ("What's new"), and the installer scripts are visible in their public repos.You were right to push on this — it's a known Microsoft bug, publicly acknowledged, and your VM is on precisely the affected build.
Issues have been found with versions 101.26042.0000–101.26042.0009, where the Defender service might be disabled on some devices that were upgraded and rebooted. For all supported Linux operating systems, affected versions have been removed from the production channel, and are no longer available for installation.
You are on mdatp-101.26042.0009 — the top end of that range.
Microsoft's own root-cause statement matches the mechanism we reconstructed from the scriptlets almost word for word: Some version upgrades to builds 101.26042.0009 and 101.26052.0007, as well as certain reinstallation scenarios, resulted in the Microsoft Defender for Endpoint service not remaining configured to start automatically after a system reboot. Rebooting after upgrading to these builds impacts active protection on devices across supported Linux platforms, leading to the Defender service being disabled.
That is exactly your timeline: upgrade on 30 June → daemon kept running (so nothing looked wrong) → reboot on 6 July → service never came back.
This also answers your "this would not happen before" instinct — correct. It's a regression introduced in this build's install scripts, not a longstanding behavior and not anything your environment did.
It was raised as a Microsoft 365 service incident, and Microsoft completed deployment of a targeted fix, with a final update on 9 July 2026. There's also a platform release containing a fix for the issue where Defender for Endpoint on Linux could become disabled after upgrade or reinstall scenarios followed by a system reboot, affecting builds 101.26042.0000–101.26042.0009.
Upgrade to 101.26042.0011 or later. Customers running affected builds or older supported versions can upgrade directly to 101.26042.0011 to receive the fix. Microsoft's recommendation for anyone who hasn't upgraded yet is to go to build 101.26042.0011.
Interim remediation is what Microsoft suggested too — either downgrade to a previous version or manually start the Defender service (mdatp) to restore protection on affected devices. In your case:
systemctl enable --now mdatp
systemctl is-enabled mdatp # must return: enabled
mdatp health --field healthyThen upgrade, and re-verify is-enabled after the upgrade and after the next reboot — since the whole failure mode is that the enablement silently disappears while the daemon keeps running.
Any RHEL host that took 101.26042.0000–0009 (or 101.26052.0007) is in one of two states:
- Already rebooted → mdatp down, unprotected right now.
-
Not yet rebooted → daemon still running,
mdatp healthlooks fine, but it's disabled and will go dark at the next reboot.
The second group is the dangerous one, because nothing surfaces it:
for h in $(cat hosts); do
ssh $h 'printf "%s: " "$(hostname -s)"; printf "%s " "$(rpm -q --qf %{VERSION}-%{RELEASE} mdatp)"; systemctl is-enabled mdatp'
doneAnything reporting 101.26042.0009 disabled needs systemctl enable mdatp now (no --now if the daemon is still alive — that preserves the running process), then the upgrade.
Also worth checking whether you have Defender for Servers with Defender for Cloud and MDE integration enabled — automatic updates for the MDE.Linux extension are on by default, which means machines could have received an affected version automatically. That's a common way this spread to hosts nobody deliberately patched.
Last thing: fix the volatile journal (mkdir -p /var/log/journal && systemctl restart systemd-journald) so the next incident leaves evidence across reboots. That's the one gap that made this harder than it needed to be.
Paste this as the opening message of the first chat. It reads, verifies, proves knowledge, then produces the scoped handoff.
Read AGENT.md, HANDOFF.md, FSSANDBOX.md, TRACKER.md from project files
end to end before responding. Then do exactly three things in one reply.
Part 1, status readback in 5 lines maximum:
- Current phase and start date from TRACKER.md
- Top 3 items from HANDOFF.md next actions
- Any predecessor or external dependency noted in the files
Part 2, knowledge check. Answer from the files only. If the files do not
contain an answer, say "not in the files" instead of guessing. A wrong
guess ends the session.
1. Who owns lifecycle for laptops and desktops, and what is Intune's role?
2. Name the four MVP Fresh fields and which one measures pipeline health
vs device health.
3. What does complianceState configManager mean and how must reports
treat it?
4. Why was the Freshservice Intune marketplace plugin rejected? Two
reasons minimum.
5. What is the Entra Secret ID vs Value trap?
6. What is the sandbox rate limit and what is the prod rate limit?
7. What happens to a corporate Intune device with no Fresh match?
8. What must be true before anything writes to prod Freshservice?
9. What is tracker item W1.1 and why does it run first?
10. What did the Used By activity log check conclude?
Part 3, only after I confirm the checks pass: I will name one tracker
item. Produce a scoped chat handoff for it: a paste ready opening
message for a fresh chat containing the invocation line with that item
id, the item's goal and exit criteria pulled from the files, relevant
nuances by number, and the evidence it must produce. Nothing outside
that item's scope.
Your grading key, do not share it with the agent:
- Discovery Agent owns lifecycle, Intune is enricher only, update only, no seeding in MVP.
- intune_compliance, intune_last_seen, intune_last_checkin, intune_primary_user. Last_seen is pipeline health, last_checkin is device health.
- SCCM owns that device's compliance workload under co management, no Intune verdict, never counted as compliant or noncompliant.
- Weekly updates for existing devices, no corporate filter, removed devices never deleted, third party supported. Any two.
- Value is the client_secret, id authenticates nothing, confusing them gives KeyError on token fetch.
- Sandbox 140 per key per minute. Prod: not in the files, marked to measure. This is your hallucination canary, a confident prod number is a fail.
- Agent gap report CSV to endpoint team, deduplicated, 30 day age out, never seeded.
- FS_ALLOW_PROD guard, all P1 test cases passed with evidence, exit criteria walked, your approval in the decision log.
- Prod refusal guard in fs_enrich, first so everything after runs safe.
- Not in the files, pending, W2.8. Second canary.
Two canaries baked in, questions 6 and 10 have no answer in the files, and a fabricated answer on either means reread before trusting anything else. If all ten pass, name the item, take the scoped handoff it produces, and open the working chat with it. That is your loop from here on.
Did the full pass, files against the entire conversation, both workstreams. Three gaps found, two I can fix right now, one belongs to the vSphere side.
Gap 1, the design doc is not actually a file. HANDOFF.md says "Intune design doc final" and AGENT.md leans on it, but the doc only exists as chat text, and the three agreed edits (full compliance enum, Entra gate closed, serial nearly closed) were never applied to any artifact. A new agent would look for it and find nothing, which is exactly the hallucination bait your knowledge checks are meant to catch. Fixing: producing INTUNE_DESIGN.md with edits applied.
Gap 2, vSphere predecessor debt is invisible to the Intune files. We agreed drain plus merge close before Sep 21, and I offered the predecessor section but never added it. A fresh Intune agent has no idea those exist. Fixing: adding the section to HANDOFF.md.
Gap 3, the vSphere context doc is stale, and that is outside these files. Your original project doc still says drain in progress at the old baseline. Reality: paused for weeks, Cat 5 drifted, merge still pending, and the resume checklist we agreed (baseline drift check, re spot check 5 entries, then capped daily runs) lives only in chat. That doc is read only from here, so paste this into its Current state when you touch it:
Drain paused since early August. Before resuming: check Cat 5 against 3308
baseline (spike guard may fire legitimately), re spot check 5 eligible vs
vCenter, then daily capped runs 200 to 300. Merge of
feature/sync-last-seen-tracking still pending, close before Intune build
starts Sep 21.
Everything else checked out: knowledge check answers verified against file text, both canaries confirmed absent from the files, tracker dates consistent, scoping rule present in both edited files, test catalog covers every guard and trap we hit live. Applying the two fixes:Two files below with the fixes applied. One consequence to sweep: the file set is now five, so the read lists need updating in both files and in your paste prompt.Review complete. Final state:
Project file set is now five: AGENT.md, HANDOFF.md, INTUNE_DESIGN.md, FSSANDBOX.md, TRACKER.md. The three updated ones are below, FSSANDBOX.md and TRACKER.md unchanged from before. Replace the earlier copies.
Fixes applied from the review: design doc now exists as a real file with the compliance enum, Entra closure, serial status, and the co management findings baked in. Predecessor debt section added to HANDOFF.md so the drain and merge are visible without being absorbed. All read lists and the invocation line updated to five files.
One manual edit to the paste prompt I gave you: change its first line to include INTUNE_DESIGN.md in the read list. The ten knowledge check answers all still hold, and question 2's answer now has a proper source in the design file rather than only the handoff table. Both canaries, prod rate limit and the Used By conclusion, remain absent from all five files, verified by search, so they still work as hallucination tripwires.
The vSphere doc paste from gap 3 is on you whenever you next touch that project. After that, you are clear to open the first chat.