Diag: intake TLS errors, check the clock before the certificates

TL;DR

Add clock sync to your provisioning checklist: every fresh image should sync time before the agent starts. Likely causes: (a) system clock minutes/hours off, (b) NTP not running or blocked (UDP 123 egress), (c) timezone confusion masking the real offset (always compare UTC).

Steps

1. Symptom (exact): forwarder log shows TLS/certificate errors reaching the intake, while DNS and TCP connect fine. Often on fresh VMs, containers without time sync, or after a hypervisor pause.
2. date -u on the host vs real UTC. More than a few minutes off is the diagnosis.
3. timedatectl / ntpq -p: is NTP running and synced? Unsynced with unreachable peers means UDP 123 is blocked.
4. openssl s_client to the intake endpoint: certificate errors that vanish when you mentally shift the clock confirm it.
5. Fix: enable and start NTP/chrony, open UDP 123 egress if blocked, wait for sync. Do not set the clock by hand as a permanent fix; it will drift again.
6. Verify: date -u correct, forwarder accepts payloads, host appears in Infrastructure. Add clock sync to your provisioning checklist: every fresh image should sync time before the agent starts.

When to use

You are seeing this: Symptom (exact): forwarder log shows TLS/certificate errors reaching the intake, while DNS and TCP connect fine. Use this skill when you run into "Diag: intake TLS errors, check the clock before the certificates".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

NTP issues are a listed agent troubleshooting topic; TLS to the per-site intake endpoints fails when the system clock is far off. Verified against live docs 2026-09-26.