🔴 Critical   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: FreeBSD 15

📖 ~1 min read

Table of contents
  1. Symptom & Impact
  2. Environment & Reproduction
  3. Root Cause Analysis
  4. Quick Triage
  5. Step-by-Step Diagnosis
  6. Solution – Primary Fix
  7. Solution – Alternative Approaches
  8. Verification & Acceptance Criteria
  9. Rollback Plan
  10. Prevention & Hardening
  11. Related Errors & Cross-Refs
  12. References & Further Reading

Symptom & Impact

Database service fails at boot, causing full application outage for dependent systems.

Environment & Reproduction

Appears after memory parameter increases or migration to hosts with lower kernel IPC defaults.

Root Cause Analysis

Configured shared memory requirements exceed kernel limits for segments or total allocation.

Quick Triage

Confirm latest parameter changes and inspect startup logs for exact allocation failure messages.

Step-by-Step Diagnosis

Compare PostgreSQL memory settings with host kernel IPC tunables to identify the mismatch.

Illustrative mockup for freebsd-15 — postgres_shm_problem
PostgreSQL fails allocating shared memory — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Adjust kernel and PostgreSQL memory parameters to a validated compatible configuration.

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Illustrative mockup for freebsd-15 — postgres_shm_solution
Kernel and database tuning restoring PostgreSQL startup — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Reduce shared_buffers and related values temporarily while scheduling capacity upgrade.

Verification & Acceptance Criteria

Service starts cleanly and remains stable during checkpoint and workload peaks.

Rollback Plan

Restore prior postgres.conf and loader tunables if new settings cause regressions.

Prevention & Hardening

Tie database parameter changes to host capacity checks and preflight validation scripts.

Linked with hugepages assumptions and concurrent memory pressure from co-located services.

Related tutorial: View the step-by-step tutorial for freebsd-15.

View all freebsd-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

PostgreSQL memory tuning docs, FreeBSD tuning handbook, and IPC parameter references.

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